sign in sign up
<<
Home , Allendeite, Carlfriesite, Cesbronite, Chesterite, Elongated octahedron, Emmonsite

Mineralogical Magazine, May 2016, Vol. 80(3), pp. 415–545 REVIEW OPEN ACCESS

A review of the structural architecture of oxycompounds

1 2,* 3 A. G. CHRISTY ,S.J.MILLS AND A. R. KAMPF 1 Research School of Earth Sciences and Department of Applied Mathematics, Research School of Physics and Engineering, Australian National University, Canberra, ACT 2601, Australia 2 Geosciences, Museum Victoria, GPO Box 666, Melbourne, Victoria 3001, Australia 3 Sciences Department, Natural History Museum of Los Angeles County, 900 Exposition Boulevard, Los Angeles, CA 90007, USA [Received 24 November 2015; Accepted 23 February 2016; Associate Editor: Mark Welch]

ABSTRACT

Relative to its extremely low abundance in the Earth’s crust, tellurium is the most mineralogically diverse , with over 160 mineral species known that contain essential Te, many of them with unique structures. We review the crystal structures of 703 tellurium oxysalts for which good refinements exist, including 55 that are known to occur as . The dataset is restricted to compounds where is the only ligand that is strongly bound to Te, but most of the Periodic Table is represented in the compounds that are reviewed. The dataset contains 375 structures that contain only Te4+ cations and 302 with only Te6+, with 26 of the compounds containing Te in both valence states. Te6+ was almost exclusively in rather regular octahedral coordination by oxygen ligands, with only two instances each of 4- and 5-coordination. Conversely, the lone-pair cation Te4+ displayed irregular coordination, with a broad range of coordination numbers and bond distances. A threshold was applied for Te4+–O links of ∼2.45 Å or 0.3 valence units with some flexibility, as a criterion to define strongly bound Te–O polymers and larger structural units. Using this criterion, Te4+ cations display one-sided 3-, 4- or 5-coordination by oxygen (with rare examples of coordination numbers 2 and 6). For both valence states of Te, examples are known of TemOn complexes which are monomeric (m = 1; neso), noncyclic finite oligomers (soro), rings (cyclo), infinite chains (ino), layers (phyllo) and frameworks (tecto tellurates). There is a clear analogy to the polymerization classes that are known for silicate anions, but the behaviour of Te is much richer than that of Si for several reasons: (1) the existence of two cationic valence states for Te; (2) the occurrence of multiple coordination numbers; (3) the possibility of edge-sharing by TeOn polyhedra; (4) the possibility for oxygen ligands to be 3-coordinated by Te; and (5) the occurrence of TemOn polymers that are cationic, as well as neutral or anionic. While most compounds contain only one or two symmetrically distinct types of Te atom, Pauling’s Fifth Rule is frequently violated, and stoichiometrically simple compounds such as CaTeO3 can have polymorphs with up to 18 distinct Te sites. There is a tendency for local symmetry features such as the threefold axis of a TeO6 4+ or the acentric symmetry of a Te On to be inherited by the host structure; the latter in particular can to useful physical properties such as nonlinear optical behaviour. We develop for the first time a hierarchical taxonomy of Te-oxysalt structures, based upon (1) valence state of Te; (2) polymerization state of TemOn complexes; (3) polymerization state of larger strongly-bound structural units that include non-Te cations. Structures are readily located and compared within this classification.

K EYWORDS: tellurium, oxysalt, crystal chemistry, polymerization, , structural heirarchy.

Introduction

*E-mail: [email protected] TELLURIUM (Te) is an unusual element in that its DOI: 10.1180/minmag.2016.080.093 cosmic abundance is greater than that of any other

© 2016 The Mineralogical Society A. G. CHRISTY ET AL. element with an atomic number >40, as measured Housley et al., 2011; Pekov et al., 2010; Christy by relative number of atoms in C1 chondrite et al., 2016). This represents the greatest flurry of (Anders and Ebihara, 1982). Nevertheless, Te is activity in the study of Te secondary minerals since one of the rarest elements in the Earth’s crust (0.4‒ the 1970s. The majority of these new minerals are 10 ppb; Parker, 1967; Levinson, 1974; Govett, also compounds new to , and 1983; McDonough and Sun, 1995; Reimann and de possess new crystal-structure types. Crystal struc- Caritat, 1998) and also in seawater (up to 0.0009 ppb; tures are now known for 55 of the ∼80 Te Andreae, 1984; Lee and Edmond, 1985). It is thus oxyminerals. It is of particular interest that the Te 3 to 5 orders of magnitude less abundant than other show a wide range of polymerization, even-number elements that are nearby in the somewhat analogous to silicates: examples range 4+ 2– 6+ 6– periodic table, such as and , and is in from isolated [Te O3] and [Te O6] anions to fact rarer than platinum or . complex three-dimensional frameworks. The The extreme depletion of Te in the Earth’s crust is analogy to rock-forming silicates is strengthened probably due to its strongly siderophile character at by the observation that, in a locality with an high pressure, which resulted in much primeval Te unusually large number of tellurate species, there being sequestered in the core, and the small appears to be a correlation between polymerization amounts of Te in the outer layers of the Earth state and both the early or late position of a mineral arriving after core formation in a “late veneer” in the local paragenetic sequence, and the (Wang and Becker, 2013). The extreme scarcity of abundance of ‘network-modifying’ species such Te makes it all the more remarkable that there are as Cu2+ (Christy et al., 2016). ∼160 Te minerals described from Nature: ∼3% of A search of the Inorganic Crystal Structure all known species. Christy (2016) showed that most Database (ICSD) and recent literature has found chemical elements show a power-law dependence good-quality crystal structures for 703 compounds, between their abundance in the Earth’s crust and the in all. The number of structures referenced per year number of mineral species in which they are for the present study suggests that the rate of essential constituents. Other elements that are synthesis and structure refinement has been major constituents of 150–200 species are much increasing through time, and that 40 new more abundant, such as Ce and Ni, present in the compounds and structures per year may now be crust at 33 and 105 ppm, respectively, according to typical (Fig. 1). Thus, the current interest in both Taylor and McLennan (1985). Conversely, if Te synthetic and natural Te oxycompounds, along with followed the typical trend, there would be only the anomalously large number of the latter, justifies seven Te minerals. Tellurium is, in fact, the most a review of their structural chemistry. It should be extreme example of an element that forms an noted that new compounds appear in the literature anomalously large number of distinct species in the constantly, but we had to stop updating our working Earth’s crust. Telluride minerals, containing Te as an list in mid-2015, in order to avoid repeated anion, are probably best known, and are well studied shuffling of the database and the associated risk due to their association with gold in epithermal Au– of introducing errors. Te deposits (cf. Cook and Ciobanu, 2005; Ciobanu Examination of the known structures of Te et al., 2006), often related to alkaline magmatism oxycompounds reveals extraordinary diversity (e.g. Jensen and Barton, 2000). Rare sulfosalts are due to a combination of factors, namely: (1) Te also known in which cationic Te4+ plays a role may occur as Te4+ or Te6+, which are of comparable analogous to As3+, such as the -group stability under atmospheric conditions, so mineral goldfieldite, ideally Cu102(TeS3)4S(Trudu compounds also occur with both oxidation states and Knittel, 1998). Hence, Te can adopt either coexisting. (2) Te6+ is almost invariably octahed- anionic or cationic roles as a chalcophile element, rally coordinated by oxygen (Christy and Mills, 6+ like As and Sb. Also, like those elements, it oxidizes 2013). The Te O6 group is strongly bound, in that readily to form secondary oxycompounds under the average Te–O bond valence is unity. In contrast, near-surface conditions. About half of the known Te Te 4+ has a stereoactive lone electron pair, and may minerals are such tellurites and tellurates. adopt a wide range of coordination . The recent explosion of new secondary mineral Usually, three to four are strongly bound to species, particularly from Otto Mountain, form an asymmetric coordination polyhedron, but , has seen publication of descriptions there may also be several other neighbours at longer for 14 new Te minerals from 2010 up to September, distances (Christy and Mills, 2013). (3) As noted 2015 (Kampf et al., 2010a;Backet al., 2011; above, TeOn polyhedra polymerize readily to form

416 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

FIG. 1. Number of crystal structure references cited per year for the current study.

oligomers, chains, layers and frameworks. These repulsion, although edge-sharing of non- units also link readily to other strongly-bonding tetrahedra and 3-coordination of oxygen atoms are cations to form heteropoly structural building units. seen in beryllosilicates and zincosilicates, where (4) The geometries of TeOn polymers are even more the lower cation valence decreases repulsion, and flexible than those of silicates, in that the polymers gives a small effective non-bonded radius relative may contain Te with various coordination numbers, to bond distances (O’Keeffe and Hyde, 1981). The and may carry not just negative or zero net charge, longer bond distances make such geometries but may also be positively charged in Te ‘salts’.For possible for Te–O polyhedra as well. 4+ + example, a [Te2 O3OH] infinite layer cation can be A structural hierarchy for silicates (Bragg, 1930; identified in (Te2O3OH)(NO3) (Anderson et al., Zoltai, 1960; Liebau, 1985) is used widely to 4+ + 1980), while the [Te (OH)3] has been organize classic textbooks such as Deer et al. recently identified in the structure of Na11H[Te (1966). More recent schemes, such as those for (OH)3]8[SO4]10(H2O)13 by Mills et al. (2016). (5) borate (Hawthorne et al., 1996) and minerals Te polyhedra readily share edges, as well as corners, (Hawthorne et al., 2000), render intelligible the in contrast to SiO4 tetrahedra. (6) Oxygen may be diversity of these large, complex classes, highlight coordinated by three Te4+, as in winstanleyite, structure-composition-property relationships and TiTe3O8 (Bindi and Cipriani, 2003). This possibil- facilitate comparison between species, and also ity does not arise in conventional silicates because aid in applying group nomenclature (Mills et al., the short Si–O distance causes strong Si…Si 2009b). A major objective of the present study is to

417 A. G. CHRISTY ET AL.

create such a structural hierarchy for Te smoothly varying function of two parameters. The oxycompounds. equation most often used is r = r0 – blns, where: r0 In NMR spectroscopy, a concise ‘Q notation’ to is the distance at unit bond valence, and b,a describe polymerization states of silicate species, in ‘softness’ parameter (Brown and Altermatt, 1985; which ‘Qn’ (n =0–4) designates silicate tetrahedra Brese and O’Keeffe, 1991; Brown, 2002). Bond with n bridging oxygen atoms and, by implication, valences and their sums on a central atom are 4-n non-bridging oxygen atoms (cf. Lippmaa et al., powerful crystallographic tools for distinguishing 1980). It would be convenient to use a similar species of similar scattering factor, but different 2– notation in the present study for TeOn polyhedra. valence, and for identifying species such as O , – However, the original symbology makes the OH and H2O and bonds when H cannot assumptions that (1) the coordination of Si is be located in structure refinements. always 4; (2) the coordination of O by Si is either 1 While a universal softness value b = 0.37 Å is (non-bridging) or 2 (bridging) and, concomitantly; often assumed (e.g. Brown and Altermatt, 1985; (3) the number of non-bridging oxygen atoms is the Brese and O’Keeffe, 1991), it has become apparent same as the number of next-nearest neighbour Si that this does not model the bonding behaviour well atoms. For Te, all three of these assumptions are for many heavier atoms. Several alternative para- invalid, as they are violated as a result of variable Te metrizations for particular species have been (CN), plus the possibilities of published in recent years [e.g. for Pb2+ by edge-sharing and CN3 oxygen. More information Krivovichev and Brown (2001); U6+ by Burns is needed to fully specify the polymerization state et al. (1997); Tl1+ by Locock and Burns (2004); and of a Te cation, including the numbers of oxygen Sb3+ and Sb5+ by Palenik et al. (2005), Sidey et al. ligands connected to 1, 2 or 3 Te cations, and the (2009) and Mills et al. (2009a)], and we examined number of edges (i.e. 4-rings, Te–O–Te–O) shared the available structural data for Te4+–O, Te4+–Cl between Te polyhedra. An extended notation Qabcz and Te6+–O bonds in a recent paper (Mills and can do this using four single-digit integers: a = Christy, 2013). For Te4+‒O, we obtained the number of CN1 oxygen atoms, b = number of CN2 parameters r0 = 1.9605 Å and b = 0.41 Å, while for 6+ oxygen atoms, c = number of CN3 oxygen atoms Te ‒O, we obtained the parameters r0 =1.921Å and z = number of shared edges. The total Te CN = and b = 0.56 Å. We considered all Te‒O distances a + b + c, the corresponding number of oxygen out to 3.5 Å as at least weakly bonded. Conversely, ligands per Te is a +½b + ⅓c, and the number of Te 4+ showed a broad distribution of coordination next-nearest Te atoms is b +2c – z. The original numbers from 3 to 12, with two modes at CN6 and silicate Qn would be written Q(4–n)n00 in the CN8 (fig. 1 in Mills and Christy, 2013). The extended notation (Q0 ≡ Q4000,Q1 ≡ Q3100··· distribution of Te4+‒O bond distances is also Q4 ≡ Q0400). Note that 0 ≤ z ≤ ½p( p–1), where bimodal (Fig. 3). Thus, the oxygen neighbours of p = b + c. Te 4+ separate into two groups: strongly-bound Avery large number of different Qabcz states can ligands on the opposite side of the Te from its occur. For 4-coordinate Te alone, there are 80 stereoactive lone electron pair, with bond valences possibilities, and 17 of these are found in the typically 0.3–1.3 valence units (vu) (corresponding structures of the present study. In order to illustrate to a distance of 1.85–2.45 Å), and more distant the value of the notation, the corresponding topolo- ligands, with bond valences usually < 0.15 vu gies are shown very diagrammatically in Fig. 2. (2.74 Å). When three short Te4+‒O bonds are 4+ present, the Te O3 is invariably a rather symmetrical trigonal pyramid, with oxygen atoms Te–O bond length and polyhedral geometry at three of the four corners of a , and the lone pair of the Te directed towards the fourth vertex ‘Bond valence’ is a parameter that expresses the (Fig. 4a); any more distant oxygen atoms are on the strength of a between a cation and an same side of the Te as the lone pair. An apparently anion in terms of the effective number of electron unique alternative to this geometry for 3-coordin- pairs involved in bonding. It is thus a generalization ation is seen in Nd[Te2O5]Br, where the three Te‒O of the concept of ‘bond order’, well entrenched in bonds are coplanar, forming a ‘T’-shape (Tarasov organic chemistry (IUPAC, 1997), and of the et al., 1996; described as structure #285 below). 4+ “electrostatic bond strength” of Pauling (1929). Te O4 may be either pyramidal, with four The bond-valence model relates bond distance, r,to O‒Te‒O angles approximately equal (Fig. 4b), or bond valence, s, for a given cation‒anion pair via a have the oxygen atoms at the apices and two

418 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

abcz FIG. 2. The 17 distinct Q states that are observed for 4-coordinate Te in this study. The central Te atom is dark green, next-nearest neighbour Te atoms are light green and oxygen atoms are red. Examples of all of these in real structures will be depicted in later figures. In some cases, the topology corresponding to the Q number is not unique: for example, there is a different Q0132 configuration to that shown in which an edge is shared between a CN2 oxygen atom and one of the CN3 oxygen atoms.

equatorial positions of a trigonal bipyramid, with ∼1 Å away from the Te atom, which is consistent the lone pair replacing the missing ligand (Fig. 4c). with the centre of lone-pair electron . 4+ The rarer examples of Te O5 approximate octahedra However, the Te–O distances within a given with the lone pair replacing one ligand (Fig. 4d). polyhedron could show a large variance, and the 4+ Subsequent investigation of the Te O6 subset of radius of the sphere of oxygen atoms increased these data by Christy and Mills (2013) showed that, linearly with the tellurium lone-pair distance although the Te–O distances within a given (Christy and Mills, 2013). The volume of the 4+ polyhedron could show a large variance, the Te O6 polyhedron varied, depending on both the 4+ oxygen atoms of a Te O6 polyhedron (including sphere radius and the uniformity of the distribution long bonds) generally fall very nearly on the surface of oxygen atoms over the sphere’ssurface.The of a sphere, not centred on the Te, but on a point polyhedra ranged in volume from nearly twice that

419 A. G. CHRISTY ET AL.

4+ FIG. 3. Overall distribution of Te ‒O bond distances for the data of Mills and Christy (2013).

4+ predicted for a regular Te O6 octahedron, when the refinements are available. Where multiple refine- oxygen atoms are uniformly distributed and the lone ments were available for a compound, one of the pair is highly stereoactive, to 20% less than that of a better ones was selected. Structures with obvious regular octahedra, when the oxygen atoms are errors or that were of solid-solution variants of a crowded on one side of the sphere. Extreme pure end-member were usually rejected. The flexibility in the volume of coordination polyhedron dataset includes 55 mineral species, about two- is, thus, another feature of lone-pair cations, such as thirds of those described to date. Te 4+, which can contribute to their accommodation in a wide range of crystal structures. A further unusual feature, occasionally noted, is Chemical constituents that bonding interactions of lone-pair cations are not limited to those of the conventional cation‒ The frequency of occurrence of specific elements as anion type. Christy and Mills (2013) found that the essential constituents in these 703 compounds is 4+ most compressed Te O6 polyhedra also showed shown on periodic tables in Fig. 5. Apart from Te and short distances between the lone pair and large O, the most common constituents in the mineral cations, such as K or Ba and/or other Te4+ cations, species are Cu and Pb (22 out of 55), H (21), Cl (9), suggesting that weak monopole‒dipole (K,Ba)‒ Fe (8) and Zn (6). While H, Cu, Cl and Pb are also lone-pair and dipole‒dipole Te4+‒lone-pair inter- important in the dataset as a whole, including actions also help to stablize the relevant structures. synthetic compounds (223, 70, 68 and 42 compounds These non-classical ‘bonds’ complicate the appli- respectively out of 703), many of the latter also cation of the bond-valence model to structures include Mo (77), Na (73), K (65), N (49), Ba (48) and containing stereoactive lone pairs. P (38). The alkali metals Na and K are common as Mills and Christy (2013) verified the strong counteranions in many laboratory-crystallized Te preference of Te6+ for octahedral geometry: that oxysalts; while the number of N compounds is 6+ dataset included 100 examples of Te O6 octahe- boosted by the analogous use of the ammonium ion, + dra, plus another five where six additional oxygen NH4. The anomalously large number of Mo atoms lay near the cut-off distance, but only 13 compounds is due to the large number of salts of 6+ 6+ 6– examples of other coordinations. Examples of the tellurohexamolybdate anion, [Te Mo6 O24] , polyhedra with CN4‒6 are shown in Fig. 4e‒g. that have been prepared, while the majority of P compounds are hydrogen-bonded adducts of Te(OH)6 with alkalis and various phosphate anions. The chemical and structural diversity of Te The large proportion of Cu, Pb and H minerals is oxycompounds consistent with these elements, like Te, showing unusually high mineral diversity (Christy, 2015), In the current study, we examine the 703 Te and the common association of primary telluride oxycompounds for which good structure minerals with sulfides of Cu and Pb. It is surprising

420 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

4+ FIG. 4. Monomeric TeOn anions. Lone-pair electron concentrations on Te cations are depicted by small light-green 4+ 2– spheres, reflecting their stereochemical role as ‘pseudo-anions’.(a)[Te O3] in , CuTeO3 ·2H2O (Effenberger, 4+ 4– 1977); (b) square pyramidal [Te O4] in nabokoite, K[Cu7(TeO4)(SO4)5]Cl (Pertlik and Zemann, 1988); (c) ‘trigonal ’ 4+ 4– prism-1 coordinated [Te O4] in , TeO2 (Kholodkovskaya et al., 1995); (d) Capped trigonal pyramid 4+ 4– [Te O4] deduced to be a component of a layer anion in BiTe2O5Cl (Berdonosov et al., 2007); (e) ‘octahedron-1’ 4+ 6− 6+ 2– coordinated [Te O5] in Ba2Te(PO4)2O (Kim et al., 2010); ( f ) Tetrahedral [Te O4] in Cs2TeO 4 (Weller et al., 6+ 4– 1999); (g) trigonal bipyramidal [Te O5] in Cs2K2TeO 5 (Untenecker and Hoppe, 1986a); and (h) octahedral 6+ 6– [Te O6] in mcalpineite, Cu3TeO 6 (Falck et al., 1978a).

that so few secondary Te minerals containing As, Definition of Te4+ coordination and structural Sb and Bi are known, as these are also minera- unit logically diverse chalcophile elements. Syntheses of many Cu and Pb tellurates were probably Mills and Christy (2013) chose 3.5 Å as a cutoff attempted because of the importance of such distance for inclusion of weak bonds to oxygen in phases as minerals. the Te4+ coordination sphere. The corresponding

421 A. G. CHRISTY ET AL.

FIG. 5. Periodic table of elements, colour-coded according to the frequency of specific elements as essential constituents in all the crystal structures of this study (above) and in mineral species only (below). All structures include Te and O (black).

422 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS bond valence is ∼0.023 vu. In contrast, the current although it should be noted that, while the study is concerned primarily with the strongest distribution is little changed for Te4+-only com- bonds of a structure, which define structural pounds (for which the numbers are, respectively, 1, building units. For this study, we divide the 530, 257, 24, 1), the small sample of mixed-valence ‘primary’ and ‘secondary’ Te 4+–O bonds at the compounds show a much greater preference for 4- minimum in the probability distribution between and 5-coordination (frequencies for CN = 2, 3, 4, 5 the two modes of Fig. 2. The threshold bond and 6 are 0, 5, 14, 13 and 1, respectively). distance is thus 2.40–2.45 Å, corresponding to a We have classified the diverse Te-bearing bond valence of 0.34–0.30 vu, using the bond- moieties using a set of nested criteria, as follows: valence parameters of Mills and Christy (2013). (1) Structures are separated into three oxidation- Note that this division is consistent with Hawthorne state taxa: those that contain only Te4+ as an (2014) and references cited therein, who use a bond essential major constituent, those that contain only balance of ∼0.30 vu to differentiate, in crystal Te 6+, and those that necessarily contain both Te4+ structures, between the more strongly bound and Te6+. (2) Within each oxidation-state taxon, we ‘structural unit’ and weakly bound ‘interstitial consider only the Te and its strongly-bound oxygen complex’. The bond-valence threshold identifying atoms. The next level of subdivision is on the basis bonds that form the structural unit is employed with of dimensionality of the TemOn species. By analogy some flexibility. The smaller divalent octahedral with the silicates (e.g. Deer et al., 1966), we use the cations Mg, Zn, Fe2+ and Mn2+, with bond-valence categories (dimensionality taxa): neso (m = 1), soro close to 0.33 vu, are part of the structural unit if they (non-cyclic finite groups with m > 1), cyclo (finite bond to tellurate oxygen atoms. However, for groups containing a ring of at least 3 Te), ino 2+ Cu O4+2 octahedra, elongated due to Jahn-Teller (infinite chains), phyllo (infinite layers) and tecto distortion, it was usually the case that only the four (infinite frameworks). When more than one distinct shortest bonds were strong enough to be included. type of TemOn group is present, the highest- Weaker bonds to these small cations were some- dimensional group with largest m and n determines times included, if needed to preserve the integrity of the classification. (3) Within each dimensionality a well-defined coordination polyhedron. taxon, species are arranged in an order that Conversely, the larger divalent cations Ca, Sr, Ba facilitates further subdivison, if justified. Cyclo-, and Cd typically occurred with CN > 6 or a mixture ino- and phyllotellurates are first separated depend- of sixfold and higher coordination numbers, and ing on whether there is a single or multiple ring/ were not generally included, unless they occurred chain/layer. They, along with neso/soro/tecto cases, on sites that were occupied by small cations in are then ordered according to the number of Te and isostructural compounds. Other large cations with anions in the finite complex or, for infinite CN ≥ 7 (e.g. REE3+,Zr4+ and Th4+) or highly polymers, the translational repeat unit. (4) Finally, irregular coordination (Pb2+ or Bi3+) were similarly we consider linkage to non-tellurium cations to 6+ excluded from the structural unit, except for U On make larger heteropolymeric ‘structural units’. polyhedra (n =6–8). The dimensionality of the Note that consistent focus on Te oxyanions heteropoly structural unit was often higher than that sometimes to rather counterintuitive divisions of the Te alone, as is apparent below. between the ‘Te oxyanion’ and the ‘rest of the When long bonds are excluded, the ranges of structural unit’. For example, on the basis of coordination numbers for the Te–O bonds included highest-valence bonds, the structure of mroseite, 4+ 4+ in the present study were between 2 and 6 for Te Ca2Te 2 O4(CO3)2, can be divided into two weakly- and between 4 and 6 for Te6+. The ‘2-coordinate’ bonding Ca2+ cations, two carbonate groups and a 4+ 0 Te of Bi2(TeO3)2O has additional ligands at just neutral [Te2O4] residual complex that consists of a over 2.5 Å (Mercurio et al., 1998), while the 6- pair of edge-sharing TeO3 pyramids (cf. Fischer coordinate examples have the pyrochlore structure et al., 1975). The formula as written above type, with Te4+ in octahedral coordination (Loopstra emphasizes this analysis. However, one oxygen and Goubitz, 1986; Weber and Schleid, 2000). The atom of each carbonate also links to a Te via other polyhedra are all of the types shown in Fig. 3 a bond that is strong enough to fall within the bond- 6+ above. For 428 symmetrically distinct Te On valence threshold, to make a larger structural unit polyhedra, frequencies were 2, 2 and 424 for n = that is a finite carbonatotellurite cluster 4– 4, 5 and 6, respectively. For 846 symmetrically [Te2C2O10] . This can be written hierarchically 4+ distinct Te On polyhedra, frequencies were 1, 535, so as to emphasize the carbonate groups, while not 271, 37 and 2 for n = 2, 3, 4, 5 and 6, respectively, showing the full Te coordination, as [(Te2O4)

423 A. G. CHRISTY ET AL.

4– (CO3)2] , or alternatively, so as to show the Te at least one threefold rotation axis, which enhances coordination, but breaking up the carbonate groups, the number of trigonal and cubic Te6+ phases. 4– [(CO2)2(Te2O6)] . In the Tables below, mroseite is The polarity due to lone-pair stereoactivity in 4– 4+ classified as having an edge-sharing [Te2O6] Te , in combination with the capacity for local dimer, but both versions of the structural formula symmetry inheritance by the structure, suggested are used in the tables and text below, depending on that there might be a dependence of centro- context. Other compounds, in which oxygen atoms symmetry on Te valence. However, the percentages are shared by Te and other high bond-valence of Te4+ and Te6+ structures lacking a centre of cations, are treated similarly, that is, with more inversion were, respectively, 18.9% (71 out of 375) intuitive or compact versions of formulae alongside and 17.5% (53 out of 302), not significantly structural formulae that emphasize Te environments. different from each other or the overall average of Because the C‒O links in mroseite have very high 18.6%. A higher proportion of acentric structures bond valence (∼1.33 vu), in order to avoid did occur for the mixed-valence structures (7 out of overbonding of the oxygen, the bond from Te to 26 = 26.9%), but this is also insignificant, given the the carbonate oxygen atom is longer and weaker small sample size. Further subdivision of the than the other Te‒O bonds: 2.313 Å = 0.42 vu using dataset by Te polymerization and coordination the parameters of Mills and Christy (2013), as number did reveal two small groups with signifi- opposed to 0.80‒1.32 vu for the other Te‒O bonds. cantly high proportions of acentric structures. This Similar weak bonding is observed when Te shares was the case for eight out of 24 of the structures 4+ an oxygen atom with other high bond-valence with isolated Te O4–5 polyhedra and five out of cations, and the need to reduce bond valence can nine structures with mixed-valence layer anions, increase the Te coordination number. Out of the 24 suggesting that there is a slight tendency to 4+ examples of TeO5 polyhedra in Te -only com- inheritance of polarity. pounds, 16 (67%) have Te4+‒O‒P5+,Te4+‒O‒As5+ The structures in the present study markedly or Te4+‒O‒Se4+ links, where the non-Te cation violate ‘Pauling’s Fifth Rule’ that “the number of makes a bond of 1.25‒1.33 vu. Interestingly, Te4+ essentially different kinds of constituents in a compounds with S6+ and V5+ do not show the same crystal tends to be small” (Pauling, 1929), although trend, because they tend instead to have very Burdett and McLarnan (1984) noted that there is no strongly bonded CN1 oxygen atoms on the non-Te a priori reason for such parsimony, except as an cation, thus reducing the valence of the bond to the indirect corollary of some of Pauling’s other rules. bridging oxygen atom. For both Te4+ and Te6+, the average number of symmetrically distinct polyhedra per structure is Crystal structure symmetry and complexity greater than unity, there being a total of 846 + 428 = 1274 distinct polyhedra for the 703 structures. The Te oxysalts in the present study show a nearly Fig. 7 shows the percentages of the 375 Te4+-only, even split between Te valences: the dataset contains 302 Te6+-only and 26 mixed-valence structures that 375 structures with Te4+ only, 302 with Te6+ only, have different numbers of symmetrically distinct Te and 26 with Te in both valence states. Interestingly, sites. Structures with larger numbers of distinct sites the distribution of structures between different are generally less numerous, although a quarter of crystal systems is quite distinct for the different Te 4+-only compounds still have between 3 and 5 valence states. As shown in Fig. 6, structures with distinct Te sites. The Te4+-only compounds also only Te4+ are significantly more likely than average include one example each of structures with 9, 10 to be monoclinic or orthorhombic, and less likely to and 18 distinct Te sites. The last of these is a be trigonal, while the converse is true for structures polymorph of CaTeO3 (Stöger et al., 2009), that have only Te6+. Structures that include both dramatically demonstrating that simplicity of valences are particularly likely to be orthorhombic, formula does not imply simplicity of structure. while having surprisingly few triclinic examples. These differences suggest that, to a degree, the symmetry of the overall structure inherits (or at least Detailed tabulation and descriptions of Te is influenced by) the point symmetry of the Te oxysalt structures oxyanion. The low symmetry of coordination Te–O complexes polyhedra such as those of Figs 4c‒d may make 4+ low-symmetry Te structures more numerous, The diversity of TemOn polymers is summarized in while TeO6 octahedra (Fig. 4h) are likely to have Tables 1 through 7, which order the different Te‒O

424 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

4+ 6+ FIG. 6. Distribution of crystal structures among crystal systems for structures with Te only, Te only, both valences and all structures. Key: Hex = hexagonal; Tetr = tetragonal; Trig = trigonal; Tricl = triclinic; Mon = monoclinic; Orth = orthorhombic.

topologies according to the hierarchical principles The finite oligomeric (soro and cyclo) Te4+ given above. These tables serve, additionally, as an oxyanions of Table 1 have the topologies shown in index for the listings of individual structures that Fig. 8. The numbers of Te atoms in these complexes follow in Tables 8–26. These tables have been range from 2 to 8, although the structure number deposited with the Principal Editor of ranges of Table 1 make it clear that some configura- Mineralogical Magazine and are available from tions are strongly preferred: we have 20 examples of www.minersoc.org/pages/e_journals/dep_mat_mm. the trimer Te3X8 (Fig. 8g), 16 of the simple dimer 6+ html. Note that the tables separate Te X6 monomers Te 2X5 (Fig. 8a) and 14 of Te4X11 (Fig. 8k). All of into two groups: compounds that contain anionic these groups are finite linear chains of corner-sharing (6–x)– [TeO6–x(OH)x] groups and those that contain TeO n polyhedra, but while the dimer has Te in only neutral Te(OH)6 which form hydrogen- 3-coordination, the other common anions show a bonded structures with cations, anions, H2O and tendency to alternate between 3-coordinated and 4- polar organic molecules. For conciseness, specific coordinated Te, which is also widespread among the structures are referenced below by the unique less usual polymers (cf. Figs 8c,g,j,k,m,o). Tellurium ordinal number that they are assigned in Tables in five-fold coordination is rare, and seems to be a 8–26 (deposited), where the corresponding litera- characteristic of compounds that contain other highly ture reference is cited. These structure numbers will electronegative cations such as P,As and Se (Figs 8e, be prefixed with ‘#’ and highlighted in boldface. f,i). Corner-linkage of TeOn polyhedra through a

425 A. G. CHRISTY ET AL.

4+ 6+ FIG. 7. Frequencies of structures with different numbers of distinct Te sites for Te -only, Te -only and mixed-valence compounds.

2-coordinate bridging oxygen atom is by far the most bridging oxygen atom is split between two half- common polymerization mechanism, but there are occupied positions, suggesting that the crystal also examples of edge-sharing through two such structure as published shows an average of oxygen atoms (Figs 8b,e,j,o) and linkage through 3- disordered zweier chains Te2X6. The stoichiomet- coordinate oxygen atoms (Fig. 8h). The wide range rically simplest chain type that occurs is a zweier of possibilities available allows formation of isomers edge-sharing chain of CN4 Te, Te2X4. Note that if with the same composition, but different topologies – all cations are Te4+ and all X are O2–, then this is a 0 Figs 8b and 8c provide an example. Most of the neutral complex [Te2O4] rather than a chain anion, polymers are unbranched soro chains, although as is the case in the example Ag(TeO2)(NO3)of Fig. 8l shows an open-branched pentamer, Fig. 8n Fig. 2a (#282). The mineral telluroperite, is a cyclo 6-ring, and Fig. 8i defies classification in Pb3TeO 4Cl2 =Pb2(PbTeO4)Cl2, contains topo- the scheme of Liebau (1985), because its three CN5 logically similar chains in which the cations Pb2+ Te atoms are Q3111 in our extended Q notation, and Te4+ are disordered in a 1 : 1 ratio to give an – joined through a mutually shared CN3 oxygen anionic chain [PbTeO4] (#283). atom, as well as through additional bridging The most common coordination of Te in the oxygen atoms of the conventional CN2 type. chains is 4. However, CN3 also occurs in Figs 7b,e, The increased diversity of TemXn polymer g,h,j,k,m,o and CN5 in Figs 9d,j,m,n. Although topologies relative to silicates is further evidenced polymerization is usually achieved through CN2 by the chain structures collected in the present bridging oxygen atoms, the chains of Figs 9f and 9l study. Single-chain topologies are listed in Table 2 also feature edge-sharing. The repeat unit along the and depicted in Fig. 9. Note that although the first chain backbone is most often 2 (zweier), although entry in Table 2 appears to be a simple einer chain the chain of Fig. 9h is dreier, and others are vierer TeX3 in the terminology of Liebau (1985), with all (Figs 9e,f,j,m,n)orsechser (Figs 9k,l,o). The chains Te atoms translationally equivalent (#281), the in Figs 9i,m,n,o have open branches, which attach

426 4+ OXYCOMPOUNDS TELLURIUM OF ARCHITECTURE STRUCTURAL THE TABLE 1. TemOn monomers and finite polymers with Te only, found in the current study, classified by the most complex Te anion if more than one type is present.

Class Stoichiometry Descriptive notes Fig. # Structural unit heteropolymerization Structure #

neso TeX3 (trigonal pyramid) 4a none, clusters, chains, layers, frameworks 1–171 TeX4 (square pyramid) 4b none, layers 172 TeX4 (trigonal bipyramid -1 ligand) 4c clusters, chains, layers, frameworks 173–193 TeX5 (octahedron -1 ligand) 4d framework 194

soro Te2X5 (Δ–Δ)8a chains, layers, frameworks 195–206 Te 2X6 (Δ–◊)8b none, chains, layers, frameworks 207–213 ◊ ◊ 214–223 427 Te 2X6 ( = )8c clusters, chains, layers, frameworks Te 2X7 (◊–◊)8d layer 224 Te 2X8 (⌂ = ⌂)8e chains 225–226 Te 2X9 (⌂–⌂)8f framework 227 Te 3X8 (Δ–◊–Δ)8g none, chains, layers, frameworks 228–247 Te 3X9 (Δ–◊–◊)8h none 248 Te 3X11 3⌂, CN2 and CN3 bridging O 8i layer 249 Te 4X10 (Δ–◊ = ◊–Δ)8j none, layers, frameworks 250–255 Te 4X11 (Δ–◊–◊–Δ)8k none, layers 256–273 Te 5X12 ◊(–Δ)4 8l framework 274 Te 5X13 (Δ–◊–Δ–◊–Δ)8n none 275–278 Te 10 X26 open-branched decamer 8o framework 279

cyclo Te6X12 [–Δ–Δ–Δ–Δ–Δ–Δ–]8n layer 280

‘X’ = (O,OH); other symbols are ‘Δ’ =TeO3, ‘◊’ =TeO4, ‘⌂’ =TeO5, ‘○’ =TeO6, ‘–’ = corner-sharing, ‘ = ’ = edge-sharing, ‘[…]’ = entities forming closed ring. A. G. CHRISTY ET AL.

4+ 2100 FIG. 8. Finite oxycomplexes containing only Te .(a)Te2X5 (Q Te) in Cs 2Te 2O5 (#195); (b) mixed-coordination 2201 corner-sharing Te2X6 in poughite, Fe2(Te2O6)(SO4)·3H2O(#211); (c) four-coordinate edge-sharing Te2X6 (Q )in 3100 Pb3(Te2O6)Br2 (#215); (d)Te2X7 (Q ) in BaMo2(Te2O7)O4 ·H2O(#224); (e) edge-sharing five-coordinate Te2X8 3201 #226 4100 (Q ) in one polymorph of Te(AsO3OH)O ( ); ( f ) corner-sharing five-coordinate Te2X9 (Q )inTe2(PO4)2O (#227); (g)Te3X8 in Sr4(Te3O8)Cl4 (#228); (h)Te3X9 in Dy4(Te3O9)(TeO3)3 (#248)(i)Te3X11 trimer linked through two 3111 2212 CN2 and one CN3 bridging oxygen atoms in Te3(AsO4)2O3 (#254). The outer Te are Q and the central one is Q ; ( j)Te4X10 in Na2(Te2O5)·2H2O(#255); (k)Te4X11 in Yb2(Te4O11)(#268); (l )Te5X12 open-branched pentamer in Cu4(Te5O12)Cl4 (#274); (m)Te5X13 in Nd5(Te5O13)(TeO3)2(MoO4)Cl3 (#275); (n) cyclo Te6X12 in (NH4)6[Mo6(Te6O12) #280 #279 (TeO3)2O18][Mo2O7]·H2O( ); (o)Te10X26 in Nb8[Te10O26](TeO3)6O8 ( ).

to a Te cation of the chain backbone through CN2 4-membered rings are united through common oxygen in most cases, but via a CN3 bridging vertices. oxygen for the chain of Fig. 9i. Figure 9j shows a Overall, the most common chain configurations loop-branched chain, in which a succession of are corner-sharing types with alternating CN3 and

428 H TUTRLACIETR FTLUIMOXYCOMPOUNDS TELLURIUM OF ARCHITECTURE STRUCTURAL THE

4+ TABLE 2. TemOn single chains with Te only (inotellurites), found in the current study.

Stoichiometry Descriptive notes Fig. # Structural unit heteropolymerization Structure #

TeX3 see text – framework 281 Te 2X4 (… = ◊ = ◊ = …)9a none 282–283 Te2X5 (…–Δ–◊–…)9b none, frameworks 284–289 Te 2X6 (…–◊–◊–…)9c chains, layers 290–298 Te 2X8 (…–⌂–⌂–…)9d frameworks 299–301 Te 4X10 (…–Δ–◊–Δ–◊–…)9e none, chains, layers 302–306 429 Te 4X10 (…–◊–◊–Δ–Δ–…)9f none 307 Te 4X10 (…–◊ = ◊–◊ = ◊–…)9g frameworks 308–311 Te 4X10 (…–(◊–Δ)–(◊–Δ)–…)9h none 312 Te 4X10 (…–(◊–Δ)–◊–Δ–…)9i chain 313 Te 4X12 (…–◊–◊–…) with branches on CN3 oxygen atoms 9j layer 314 Te 6X14 loop-branched vierer chain with Te CN = 3 and 5 9k framework 315 Te 6X16 (…–Δ–◊–◊–Δ–◊–◊–…)9l none 316 Te 6X16 (…–◊–◊ = ◊–◊–◊ = ◊–…)9m frameworks 317–322 Te 6X18 (…–◊–(Δ–⌂)–◊–(Δ–⌂)–…)9n framework 323 Te 6X22 (…–(⌂–⌂)–◊–(⌂–⌂)–◊–…)9o framework 324 Te 8X22 (…–(◊–Δ)–◊–◊–(◊–Δ)–◊–◊–…)9p none 325

Symbols as for Table 1, plus ‘(…###…)’ = ### forming infinite chain, ‘(…##(#–#)##…)’ chain with side branch inside additional parentheses. A. G. CHRISTY ET AL.

4+ FIG. 9. Single-chain Te‒O complexes containing only Te . Chains all extend horizontally. The terms zweier, dreier, vierer, sechser imply chain backbone repeats of 2, 3, 4 and 6 Te atoms, respectively. The Q state is indicated where it is 0402 the same for all Te. More complex structures are discussed in the text. (a) Edge-sharing zweier Te 2X4 (Q ) neutral complex in Ag(TeO2)(NO3)(#282); (b) mixed-coordination corner-sharing zweier Te 2X5 anion in rajite, Cu(Te2O5) 2200 (#284); (c) four-coordinate corner-sharing zweier Te 2X6 (Q ) in schmitterite, (UO2)(TeO3)(#292); (d) five-coordinate 3200 #300 zweier Te 2X8 (Q ) in one of the TeSeO4 dimorphs ( ); (e) corner-sharing vierer Te 4X10 in chekhovichite, Bi2(Te2O5)(TeO3)2 (#302); ( f ) different order of CN3 and CN4 Te sharing corners in Te4X10 of Ho2(Te2O5)Cl (#307); 1301 (g) corner- and edge-sharing vierer Te 4X10 (Q ) in denningite, MnMn(Te4O10)(#310); (h) open-branched zweier 5+ Te 4X10 in K2(Te2O5)(#312); (i) Open-branched dreier Te 4X10 in Ba2V (Te4O9OH)O3 (#313); ( j) open-branched zweier Te 4X12 with branches attached to CN3 bridging oxygen atoms in (NH4)2W(Te2O6)O2 (#314); (k) loop-branched #315 #316 vierer Te 6X14 in Ni2(Te3O7)(TeO3)( ); (l ) mixed-coordination sechser Te 6X16 in Pb2Te 3O8 ( ); (m) corner- and 2+ 3+ edge-sharing sechser Te 6X16 in spiroffite, Mn2Te 3O8 (#318); (n) open-branched vierer Te 6X18 in Fe Fe2 (Te3O9)(TeO3) (#323); (o) open-branched vierer Te 6X22 in Te3(PO4)2O3 (#324); (p) open-branched sechser Te 8X22 in Ca4(Te4O11) #325 (TeO3)( ).

430 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

CN4 (eight instances of the zweier chain of Fig. 9b,

329 four of the vierer chain of Fig. 9e) and CN4 chains # – 330 332 327 326 333 334 331 with regularly-spaced edge-sharing links (four 328 Structure examples of the denningite-type vierer chain of Fig. 9f and six of the spiroffite-type sechser chain of Fig. 9l ). Topographic isomers are common: the four different configurations Figs 9e‒h all have the same Te4X10 stoichiometry. A chain is defined as multiple if it is possible to selectively remove some Te‒O links so as to break it layer none none none none none

framework into two or more subchains that themselves remain

Structural unit continuous. The dataset of this study contains

heteropolymerization several types of double chain, as well as a triple chain and even a quadruple chain. These are listed in Table 3, and depicted in Fig. 10. f c e g d b a h The simplest double chain found in this study is 10 the uncharged einer double chain Te2O4 of Bi3(Te2O4)(TeO3)2Cl5 (#326). The bridging oxygen atoms of each subchain make a third Te‒O bond, linking the two subchains together (Fig. 10a), to make a chain of Q1032 Te polyhedra that is almost an infinitely extended homologue of the finite trimer in Fig. 8i. All but one of the other multiple chains have zweier periodicity along the

double-; CN3 chain length, but show a remarkable range of 4 complexity in the connection patterns between chains. One of the two inequivalent subchains of ) pair 10

– Fig. 10b can be regarded as loop-branched: 1300 ◊ backbone Te are Q , but connect to additional = Q2110 Te, making 3-rings, which, in turn, link to the ◊ double-triangle 10

– 2110 4 unbranched subchain of Q Te via the CN3 bridging oxygen. The zigzag pattern of 6-rings in

chainsFig. 10c can 10 be formed through conventional corner-linkage of open-branched subchains. This and share edges to make Te is also the case for the isomeric chain of Fig. 10d, dreier open-branched chainsexcept 10 that the branches there do not link directly to dreier the other subchain, but instead share edges to form with CN3 bridging oxygen atoms 10 zweier chains; outer two are open-branched 10

chains linked through ( a (Te = Te) pair that is not part of either backbone.

chains linked through Te The only dreier double chain (Fig. 10e) has only (inotellurites), found in the current study. einer

oxygen atoms link extra Te to outer chains unbranched subchains that corner-link directly to zweier 4+ zweier with one CN3 oxygen and one chain loop-branched 10

zweier form a ribbon of 5-rings, reminiscent of the 6-rings , inner pair are of Fig. 10c. Both of these structures occur for Fe

zweier tellurates. The most complex double chain occurs zweier for the chemically simple compound Na2Te 4O9 (#332; Fig. 10f ). Each zweier subchain backbone can be regarded as loop-branched, so that the subchains are each made of linked 5-rings. However, the loops of the subchains join via a multiple chains with Te outer chains are n shared edge and two corner-linkages to form a O

m cluster Te4On in which two 3-rings are united at a common shared edge. An isolated cluster with the

3. Te 6+

26 same topology occurs for Te (Fig. 13d). It will be 4 12 14 14 16 18 24 X

X X X X X X X seen below that this ‘double-triangle’ moiety 2 5 6 6 6 8 8 12 ABLE Double chains Te T Stoichiometry Descriptive notes Fig. # Te Triple chains Te Te Te Te Quadruple chains Te Te appears to be unusually stable, recurring as part of

431 A. G. CHRISTY ET AL.

4+ FIG. 10. Multiple-chain Te‒O complexes containing only Te . Chains all extend horizontally. (a) Four-coordinate Te #326 make an einer Te 2X4 neutral complex with CN3 bridging oxygen atoms in Bi3(Te2O4)(TeO3)2Cl5 ( ); (b) loop- branched and unbranched subchains join to make a zweier Te 5X12 double-chain anion in Cd7(Te5O12)(Te2O5)Cl8 (#327); 3+ (c) open-branched subchains link to make zweier Te 6X14 with zigzag 6-rings in Fe (Te3O7)Cl (#328); (d) branches of subchains share edges to make isomeric zweier Te 6X14 in Tl2(Te3O7)(#330); (e) unbranched subchains link to form dreier 3+ Te 6X16 with ribbon of 5-rings in Fe4 (Te6O16)(Te2O6)(#331); ( f ) loop-branched zweier subchains link to form Te8X18 ‘ ’ #332 double chain with Te4X12 double triangle clusters between chain backbones in Na2(Te4O9)( ); (g) open-branched zweier triple chain Te8X24 in Te4(PO4)2O5 (#333); (h) quadruple chain Te12X26 with zweier and dreier subchains, CN3 bridging oxygen atoms and double-triangle clusters Te4X10 where central subchains link in Cd4(Te6O13)Cl6 (#334).

several larger polymers. The topology of the zweier quadruple chain which exhibits almost every triple chain of Fig. 10g is similar to that found in complexity known in Te oxyanions. It contains Te silicates for and related ‘biopyr- with CN3, 4 and 5. While the two outer chains are iboles’ (Veblen and Burnham, 1978), but with zweier, the two central chains are dreier. additional side branches. Finally, Fig. 10h shows a Furthermore, the central chains join to each other

432 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

4+ FIG. 11. Single-layer Te‒O complexes containing only Te . Unit-cell outlines are shown dashed when the projection direction is down a principal axis of the cell. The number of Te in the TemXn formula unit corresponds to the translational repeat unit for the topology in its most symmetrical configuration; the repeat unit of the actual structure may be larger. 0400 (a)TeX2 layer of square pyramids (Q Te) in Nd(Te2O4)OCl (#335); (b) most symmetrical local configuration for 1400 TeX2.5 in the disordered structure of Bi(Te2O5)Cl (#337); (c)TeX3 with CN5 Te (Q )inBi2(TeO3)(TeO2)OBr2 (#338); 0132 4+ 3+ 1+ 1+ (d) cationic (Te,Sb)2X3 layer (Q Te) with 1 : 1 ratio of disordered Te and Sb in Cu (SbTeO3) Cl2 (#339); 0401 #340 (e) cationic Te2X4 layer (Q )in(Te2O3OH)(NO3)( ); ( f )Te2X5 layer with ordered CN4 and CN5 Te in 1300 Bi4(Te2O5)O4Br2 (#342); (g) CN4 Te (Q ) forming Te2X5 layer with 6-rings in Mg(Te2O5)(#346); (h)Te3X7 layer in 1210 which 3-rings are linked via CN3 bridging oxygen atoms (Q Te) in La 2(Te3O7)2(WO4)(#349); (i)Te4X10 layer of 1300 3+ (#350 Q Te, with 4- and 8-rings in mackayite, Fe (Te2O5)OH ); ( j)Te4X10 layer of CN4 Te with 10-rings, edge- sharing pairs of Te having two rather than three bridging oxygen atoms, in one dimorph of Li2(Te2O5)(#351); (k)Te4X10 layer of CN4 Te with 10-rings, edge-sharing pairs of Te having three bridging oxygen atoms, in Tl2(Te2O5)(#352); (l )Te8X18 layer with 6-rings containing one or two CN3 Te, in (NH4)2(Te4O9)(#355); (m)Te8X18 layer with 6-rings containing zero or two CN3 Te, in K2(Te4O9) · 3.2H2O(#356); (n) convoluted Te16X36 layer with edge-sharing pairs of #357 CN5 Te and corner-sharing CN3/CN4 Te, making 3-, 4- and 12-rings, in (NH4)Rb(Te4O9)·2H2O( ); (o) loop- branched Te40X100 layer in which tubes with 4-, 7- and 8-rings, running vertically on the page, are connected via sparser tubes with 9- and 10-rings, in Ba6(Te10O25)Br2 (#359).

433 A. G. CHRISTY ET AL.

FIG. 11. Continued. through Te‒O polyhedra sharing edges and corners, ∼25%-occupied CN2 oxygen atoms (O3). Short to form again the ‘double-triangle’ cluster seen in distances mean that O2 cannot be occupied Fig. 10f. Conversely, the central chains join to the simultaneously with its three nearest O3 sites, and outer chains less conventionally, via oxygen atoms O3 cannot be occupied simultaneously with its which are CN3, as they also join to additional Te nearest O2 or its two nearest O3 sites. Figure 11b cations, so that the outer chains can be regarded as shows the most symmetrical way of satisfying these sequences of trimeric clusters resembling those of short-range order constraints, with ¾ of the Te in Fig. 8i. distorted 5-coordination (Q1220) and ¼ in the 4+ 1030 Polyhedra Te Xn polymerize further to form capped pyramidal coordination of Fig. 3d (Q ). layers, which may attain considerable complexity. Figure 11d shows a (Te0.5Sb0.5)2X3 sheet in which The simplest single layers have TeX4 square double chains of the type shown in Fig. 10a, pyramids that link via corners to form a sheet featuring CN3 oxygen atoms, are connected TeX2 (Fig. 11a), in which all Te are equivalent. All through additional Te–O–Te links to produce a 0132 + or half of these polyhedra may be capped by an sheet with Q cations [(SbTe)O3] that is additional ligand to form sheets with either TeX3 positively charged, rather than anionic. The layer (Fig. 11c)orTe2X5 (Fig. 11f ) stoichiometry. Avery in Fig. 11e has Te2X4 stoichiometry. All Te are CN4 different type of layer with Te:X = 2 : 5 is seen in and all X are CN2, but each TeX4 polyhedron shares 0401 Fig. 11b. This compound, ideally Bi(Te2O5)Cl one edge, so that it links to only three others (Q + shows considerable structural disorder, and has all configuration). Figure 11e shows the [Te2O3OH] Te equivalent in its average structure. The Te shows complex from (Te2O3OH)(NO3), which again is short distances to one capping ligand (O1), three cationic rather than anionic. However, the neutral 0 ∼75%-occupied CN3 oxygen atoms (O2) and six sheet [Te2O4] of tellurite, TeO2 (#341) has the

434 H TUTRLACIETR FTLUIMOXYCOMPOUNDS TELLURIUM OF ARCHITECTURE STRUCTURAL THE

4+ TABLE 4. TemOn single layers with Te only (phyllotellurites), found in the current study. The formula unit is the smallest possible translational repeat unit for the topology.

Structural unit Stoichiometry Descriptive notes Fig. # heteropolymerization Structure #

TeX2 CN4 Te corner-linked to make 4-rings 11a none 335–336 TeX2.5 disordered CN4 and CN5 Te making 3-rings via CN2 and CN3 oxygen atoms 11b none 337 TeX3 CN5 Te corner-linked to make 4-rings 11c none 338 (Te,M)2X3 CN4 Te linked via CN3 oxygen atoms into double chains and then via CN2 oxygen atoms into 11d none 339 435 layer Te 2X4 (>◊ = ◊<) pairs share corners to make 6-rings 11e none 340–341 Te 2X5 [–◊–⌂–◊–⌂–] 4-rings 11f none 342 Te 2X5 (–◊–) making 6-rings 11g none, layer, frameworks 343–348 Te 3X7 CN4 Te 3-rings linked via CN3 oxygen atoms to make 6-rings 11h none 349 Te 4X10 (◊–◊) making 8- and 4-rings 11i framework 350 Te 4X10 (–◊ = ◊–) link via (–◊–◊–◊–) to make 10-rings; each (–◊ = ◊–) pair shared by two rings 11j none 351 Te 4X10 (>◊ = ◊<) link via (–◊–◊–◊–) to make 10-rings; each (>◊ = ◊<) pair shared by four rings 11k none 352–353 Te 8X18 [–◊–◊–Δ–◊–◊–Δ–] and [–◊–◊–◊–◊–◊–Δ–] 6-rings 11l none 354–355 Te 8X18 [–◊–◊–Δ–◊–◊–Δ–] and [–◊–◊–◊–◊–◊–◊–] 6-rings 11m none 356 Te 16 X36 (–◊–◊–Δ–◊–◊–Δ–) chains linked through (⌂ = ⌂) pairs to make 3-, 4- and 12-rings 11n none 357–358 Te 40 X100 tubes with 4- 7- and 8-rings or 9- and 10-rings linked into looped sheet 11o none 359 4+ TABLE 5. TemOn with Te only in double layers (phyllotellurites) and frameworks (tectotellurites), found in the current study.

Structural unit Structure Stoichiometry Descriptive notes Fig. # heteropolymerization #

double layers (phyllo) CHRISTY G. A. Te 6X13 [–◊–◊–◊–] 3-rings linked through CN3 oxygen to upper or lower Te of (◊ = ◊), to make 12-rings 12a frameworks 360–362 in each sublayer

436 Te 6X14 [–⌂–◊–⌂–Δ–◊–⌂–◊–Δ–]8–rings in sublayers, [–⌂–Δ–⌂–Δ–] and [–⌂–◊–Δ–⌂–◊–Δ–] 12b layer 363 bridging layers frameworks (tecto)

4 AL. ET TeX2 cristobalite type (CN4, Q )12c none 364–365 6 TeX3 pyrochlore type (CN6, Q )12d none 366 Te 3X7 Te links to four oxygen atoms with CN 1,2,2,3 12e framework 367 Te 3X7 Te links to four oxygen atoms with CN 1,2,2,3 12f framework 368 Te 3X8 Te links to four oxygen atoms with CN 1,1,3,3 12g framework 369–373 2 Te 4X9 4-rings [–◊–◊–◊–◊–] linked through pairs of Q -◊ 12h none 374 Te 5X11 (◊ = ◊ = ◊ = ◊) linked through ◊ and CN3 oxygen to make chains of 6-rings, cross-linked by 12i none 375 perpendicular chains (–◊–◊–) making 8- and 10-rings. THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

4+ FIG. 12. Double-layer and framework Te‒O complexes containing only Te . Unit-cell outlines are shown dashed for the #360 #363 frameworks. (a)Te6X13 double layer in Zn(Te6O13)( ); (b)Te6X14 double layer in Te3(SeO3)O5 ( ); (c)TeX2 0400 0600 framework (Q ) of the paratellurite polymorph of TeO2 (#364); (d) pyrochlore framework TeX3 (Q )in Pr2(Te2O6)O (#366); (e)Te3X7 framework in KGa(Te6O14)(#367); ( f )Te3X7 framework in cliffordite, (UO2)(Te3O7) (#368); (g)Te3X8 framework of winstanleyite, Ti(Te3O8)(#372); (h)Te4X9 framework of Cs2(Te4O9)(#374); (i)Te5X11 framework of Pb(Te5O11)(#375).

same topology, but is much more deeply corru- those that point ‘up’ and those that point ‘down’ gated. When TeX4 polyhedra share three corners relative to the overall plane of the layer, and 1300 only (Q ) to form 6-rings, a Te2X5 sheet such as different up/down ordering patterns of apical Fig. 11g is obtained, topologically similar to the oxygen atoms may occur. In the present study, silicate sheet of , but less regular geometric- most examples (including that of Fig. 11g) show ally. As is the case for phyllosilicates, the non- alternation of pairs of ‘up’ and pairs of ‘down’ bridging oxygens can be distinguished between polyhedral apices. However, one of the dimorphs of

437 A. G. CHRISTY ET AL.

6+ #619 FIG. 13. Finite oligomers and chains containing only Te .(a) -sharing dimer Te2X9 in Ba3(Te2O9)( ); (b) edge- sharing Te2X10 in eckhardite, Ca2Cu2(Te2O10)·2H2O(#639); (c) corner-sharing Te2X11 in schieffelinite, Pb10(Te2O8(OH)3)2(TeO2(OH)4)2(SO4)·5H2O (#642); (d) ‘double-triangle’ tetramer Te4X18 of K2(Te4O8(OH)10) (#644 ); (e) cyclo 6-ring Te6X27, with alternation of edge- and corner-sharing in K8.5(H3O)0.5(Te6O18(OH)9) · 17H2O (#645); ( f ) edge-sharing zweier chain Te2X8 in CaTeO4 (#648); (g) corner-sharing zweier chain Te2X10 in ottoite, Pb2(Te2O10)(#655); (h) helical edge-sharing dreier chain Te3X12 in Ag3(TeO4)I (#657); (i) loop-branched zweier chain of ‘double-triangle’ clusters Te3X12 in K2(Te3O8(OH)4)(#658); ( j) helical edge-sharing vierer chain Te4X16 in Li2(TeO4) (#662); (k) corner-sharing vierer chain Te4X20 in housleyite, Pb6Cu(Te4O18(OH)2)(#663).

Li2Te 2O5 (#351) has all apices oriented in the same Figure 11i shows a Te4X10 sheet with 4- and 8- direction, similar to the micas. rings, which again is strongly analogous to a well- The trigonal Te3X7 sheet of Fig. 11h has CN2 known silicate structure, apophyllite (Colville oxygen atoms linking Te into 3-rings and additional et al., 1971). The isomeric Te4X10 structures of CN3 oxygen atoms forming 6-rings (Q1210 config- Figs 11j and 11k both have all Te 4-coordinated, but uration); note that the hybrid double chain of in 10-rings only, which requires some Te to link to Fig. 10b is actually a slice of this structure. only two others rather than three, and hence, for

438 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS some edges to be shared. In Fig. 11j, the edge- one hand, and the high-pressure stishovite structure sharing Te are Q1301 and the others Q1300, while in on the other, analogous to the transformation Fig. 11k, the edges are shared by Q0401 polyhedra mechanisms described in Christy (1993). and the others are Q2200. The isomeric pair of Figure 10d shows a rare example of Te4+ in Q0600 Te 8X18 alkali tellurite sheets in Figs 11l and 11m polyhedra that are nearly regular octahedra, with no have no shared edges, but both have ¼ of the Te in lone-pair stereoactivity, and which link to form the CN3 rather than CN4. The Te form 6-rings which pyrochlore framework. The frameworks of Figs contain one or two CN3 cations in Fig. 11l, but zero 12e‒g are all closely related, and like that of or two CN3 cations in the pseudohexagonal sheet Fig. 12d, have cubic unit cells with a ≈ 10 Å; all of Fig. 11m. The much more complex and highly can ultimately be derived from 2 × 2 × 2 super- convoluted Te16X36 sheet of Fig. 11n has Te in 3-, 4- structures of the type. The Te3X7 framework and 5-coordination, making 3-, 4- and 12-rings. of KGa(Te6O14) (Fig. 10e) is formed when ¼ of the The CN5 Te occur in edge-sharing pairs. Finally, ‘fluorite’ cations are replaced by non-Te species Fig. 11o shows an extraordinarily complex sheet and ⅛ of the anions omitted, to make a framework made by Q2200 Te cross-linking elliptical tubes in which Te are in a Q1210 configuration, linked which have 4-, 7- and 8-rings of CN4 Te. through 2 × CN2 oxygen atoms and one CN3 Analogously to the case for chains, a phyllo- oxygen atom. The isomeric cliffordite framework tellurate has a double layer if deletion of selected (Fig. 12f ) has a similar range of oxygen CN and the Te–O bonds can separate it into two distinct same Pa3 space-group symmetry, but the topology sublayers which themselves remain continuous. of linkage of the CN2 and CN3 oxygen atoms is Our dataset contains two types of double layer, as different. The structure of the winstanleyite group, 4+ seen in Table 5 and Fig. 12. The Te6X13 double M (Te3O8), is a slightly distorted fluorite super- layer of Fig. 12a has all Te CN = 4, but half of them structure in which the Te framework has Q2020 Te are Q1300, sharing corners to form 3-rings, while the linked through two CN3 oxygen atoms only; it can other half of the Te are branches off these rings, thus be represented as a 3-connected net with CN3 0311 which share edges (Q ) to link the two sublayers. oxygen at the nodes and (TeO2) groups decorating Oxygen atoms with CN3 link the edge-sharing the links (Fig. 12g). dimers to complete each of the sublayers. Figure 12h shows a more open tetragonal Te4X9 0400 Conversely, the Te6X14 double layer of Fig. 12b framework in which half the Te cations are Q , has no edge-sharing or CN3 oxygen atoms, but has forming Te4O12 rings which are arranged on a D Te in three different coordination states (Q0300, lattice complex (Fischer and Koch, 2006), analo- 1300 1400 Q and Q configurations). Like many Te‒O gous to the Ti atoms in anatase (TiO2; Howard polymers containing CN5 Te, this thick double et al., 1991) or Ca in scheelite (CaWO4; Zalkin and layer is braced by additional polyhedra containing Templeton, 1964). These Te atoms are linked to 4+ 2200 other high-charge, low-CN cations (Se O3 in form a framework through pairs of Q Te atoms, this case). making additional 4-rings. The Te5X11 framework 4+ Te On polyhedra also form a range of infinite of Pb(Te5X11) is even more open (Fig. 12i). This three-dimensional frameworks. Figure 12c shows structure has five distinct types of Te, all CN4, but the electrically neutral tetragonal framework of in four distinct Q states. Te1 (Q0222) and Te3 (Q0401) paratellurite, TeO2, and its metastable orthorhombic form edge-sharing tetramers Te3 = Te1 = Te1 = Te3, 1210 distorted variant γ-TeO2; these are polymorphs of while Q Te2 links to Te3 of one tetramer and tellurite, which has a layered structure of the type through CN3 oxygen to both Te1 of the next, so that seen in Fig. 11e. The paratellurite framework is of Te1, Te2 and Te3 form continuous chains of 6-rings interest in that it is isopuntal with the low- which run || x and lie in layers || (001). Between cristobalite form of SiO2 (Dollase, 1965), and yet these layers and cross-connecting them are can also be derived from the structure of rutile (and corner-sharing chains running || y of Q1300 Te4 the dense stishovite form of silica) by deformation and Te5, where the chain backbones ‒Te4‒O‒Te5‒ of coordination octahedra TeO6 → TeO 4+2 → TeO 4. O‒ have an asymmetrical crankshaft geometry, very Note that the Q0400 Te polyhedra are much less similar to that of the Pb‒O chains in massicot (Hill, symmetrical than SiO4 tetrahedra. The paratellurite 1985). Connections are so sparse that the smallest structure is thus a shared hettotype structure that rings to include Te4 or Te5 have eight and ten could act as a transition state for diffusionless phase members. transformations between the low-density/high- As noted above, the stereochemistry of Te6+ is temperature structure of high-cristobalite on the much less diverse than that of Te4+, so the range of

439 6+ TABLE 6. TemOn complexes with Te only, found in the current study. ‘M’ = another CN6 cation in solid solution with Te.

Class Stoichiometry Descriptive notes Figure # Structural unit heteropolymerization Structure #

neso TeX4 tetrahedral 4e none 432, 434 TeX5 trigonal bipyramidal 4f none 433–434 TeX6 octahedral 4g none, clusters, chains, layers, 375–431 (Te(OH)6 adducts) 435–618 (TeX6 frameworks anions)

soro Te2X9 (○ ≡ ○)13a none 619–620 Te 2X10 (○ = ○)13b none, chains, layers, frameworks 621–641 Te 2X11 (○–○)13c none 642–643 .G CHRISTY G. A.

cyclo Te4X18 ‘double triangle’ 13d none 644 Te 6X27 6-ring with alternating corner- and edge- 13e none 645 sharing 440

ino Te2X8 edge-sharing 13f none 646–652 Te X corner-sharing 13g none, framework 653–656 2 10 AL. ET Te 3X12 edge-sharing 13h none 657 Te 3X12 loop-branched zweier 13i none, layers 658–661 Te 4X16 edge-sharing 13j none 662 Te 4X20 corner-sharing 13k none 663

phyllo (Te,M)X3 edge-sharing, 6-rings (cation CN octahedral) 14a layers 664–666 (Te,M)X3 edge-sharing, 6-rings (cation CN trigonal 14b layers 667 prismatic) TeX4 corner-sharing, 4-rings 14c none, framework 668–670 Te 3X14 corner-sharing, 8-rings 14d none 671

tecto (Te,M)X2 distorted rutile (VO2) type 14e none 672–673 TeX3 distorted ReO3 (FeF3) type 14f none 674 Te 2X7 weberite type 14g none 675–676 (Te,M)4X12 edge- and corner-sharing 14h none 677 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

6+ FIG. 14. Layers and frameworks containing only Te .(a) Edge-sharing octahedral (Te,Fe)X3 layer in burckhardtite, 3+ 6+ 4+ 6+ Pb3(Fe Te O6)(AlSi3O8)(#666); (b) edge-sharing trigonal prismatic (Te,Mn)X3 layer in Sr(Mn Te O6)(#667); (c) corner-sharing TeX4 layer in Bi2(TeO4)O2 (#669); (d) chiolite-type layer Te3X14 of Ca5(Te3O14) (#671); (e) distorted 2+ 6+ #673 #674 rutile framework (Te,Ni)X2 of (Ni Te )O4 ( ); ( f )FeF3 (collapsed ReO3 type) framework of TeO3 ( ); (g) weberite-type framework Te2X7 of Na2(Te2O7)(#675); (h) strongly layered (Te,Fe)4X12 framework with edge-sharing 3+ 6+ in Pb3(Fe2 Te 2 O4) (#677).

polymeric complexes is also more restricted. with its ability to make a profusion of hydrogen 2– Table 6 shows that the tetrahedral TeO4 anion bonds, is the defining Te species in 59 structures, 4– (Fig. 4e) and bipyramidal TeO5 (Fig. 4f ) occur in while no less than 182 have less protonated only three structures altogether, one of which octahedral anions as their most complex Te contains both of them. Conversely, octahedral complex. Thus, isolated TeX6 octahedra are the complexes TeX6 (Fig. 4h) are extremely common. most complex Te complex in about one third of the The neutral ‘orthotelluric acid’ Te(OH)6, total database. Only five types of finite oligomer are

441 4+ 6+ TABLE 7. TemOn monomers and finite polymers with mixed Te and Te found in the current study, classified by the most complex Te anion type.

Class Stoichiometry Descriptive notes Fig.# Structural unit heteropolymerization Structure # 6+ 4+ neso Te X6 + separate Te X3 framework 678 4+ 6+ ino (MTe )Te X8 loop-branched zweier (double triangles) 15a none 679 4+ 6+ Te Te 2 X11 loop-branched zweier (3-rings) 15b none 680

4+ 6+ CHRISTY G. A. Te 2 Te 2 X12 loop-branched zweier (3-rings) 15c none 681 4+ 6+ phyllo Te Te X6 corner-sharing, 3-rings and 4-rings 15d none 682–684 4+ 6+ Te Te X6 corner-sharing, 3-rings and 5-rings 15e none 685 442 4+ 6+ Te Te X6 double triangles, 8-rings 15f none 686 4+ 6+ Te Te X6 double triangles, 4-rings 15g none 687 4+ 6+ 688–694 Te Te X7 6-rings 15h layers, frameworks AL. ET 4+ 6+ Te 3 Te X9 3-, 4- and 6-rings 15i none 695 4+ 6+ tecto Te Te X5 16a none 696 4+ 6+ 6+ 4+ Te 2 Te X8 Te linked by edge-sharing dimers of Te 16b none 697 4+ 6+ Te 2 Te X8 cross-linked chains of double triangles 16c none 698 4+ 6+ 6+ 4+ 4+ Te 2 Te 2 X11 kagome Te +Te layers cross-linked by edge-sharing dimers of Te 16d none 699 4+ 6+ Te 3 Te X12 ordered pyrochlore framework 16e none 700 4+ 6+ Te 3 Te X12 modified pyrochlore framework 16f none 701 4+ 6+ 6+ 4+ Te 2 Te 3 X14 kagome Te layers cross-linked by edge-sharing dimers of Te 16g none 702 4+ 6+ Te 3 Te 5 X23 modified pyrochlore framework 16h none 703 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

4+ 6+ FIG. 15. Te‒O chain and layer complexes containing both Te (light green) and Te (dark green). (a) Loop-branched 4+ 3+ 6+ ‘ ’ 3+ 4+ 6+ #679 zweier chain (Te ,Bi )2Te X8 containing double triangle motifs in Bi[(Bi Te )Te O8]( ); (b) loop-branched 4+ 6+ 4+ 6+ 4+ 6+ 4+ zweier chain with 3-rings Te Te 2 X11 in Cd2Te Te O7 =Cd4(Te Te 2 O11)(Te O3)(#680); (c) loop-branched zweier 4+ 6+ 4+ 6+ 4+ 4+ 6+ chain with 3-rings Te2 Te 2 X12 in Cd4(Te2 Te 2 O12)(Te O3)2 (#681); (d) layer with 3- and 4-rings in (NH4)(Te Te #682 4+ 6+ 4+ 6+ 4+ 6+ #685 O5(OH)) ( ); (e)layerTe Te X6 with Te and Te making 3- and 5-rings in Te Te O4(OH)2 ( ); ( f )layer 4+ 6+ 4+ 6+ 4+ 6+ Te Te X6 with double-triangle clusters and 8-rings in Ag2(Te Te O6)-I (#686); (g)layerTe Te X6 with double- 4+ 6+ 4+ 6+ triangle clusters and 4-rings in Ag2(Te Te O6)-III (#687);(h) strongly corrugated layer Te Te X7 of 6-rings in SrCu 4+ 6+ 4+ 6+ 4+ 6+ (Te Te O7) (#688); (i) 6-rings of Te sharing corners through Te in Te3 Te O9 (#695).

documented. Octahedral dimers may share faces of more complex polymers in Figs 10f and 10h, and 3303 4202 (Q Te 2X9, Fig. 13a), edges (Q Te 2X10, a 6-ring Te6X27 with alternating corner-sharing and 5101 Fig. 13b) or corners (Q Te 2X11, Fig. 13c). The edge-sharing of octahedra (Fig. 13e). only larger oligomers are a bicyclic ‘double Table 6 shows that the variety of infinite Te6+ triangle’ tetramer Te4X18 (Fig. 13d), which is a chains is similarly limited. Only single chains are 6+ 4+ Te analogue of the Te clusters that occur as parts known. Zweier chains may be edge-sharing Te2X8

443 A. G. CHRISTY ET AL.

0601 (Fig. 13f ) or corner-sharing Te2X10 (Fig. 13g). edge-sharing: half the octahedra are Q and the 0602 Edge-sharing dreier chains Te3X12 occur (Fig. 13h), other half Q . In this framework, dense zigzag as do edge-sharing vierer Te 4X16 (Fig. 13j)and columns || z share polyhedral edges in the y direction corner-sharing Te4X20 (Fig. 13k). Note that the vierer to define layers, which in turn are linked into a periodicity of the latter is determined by having framework via relatively sparse Te‒O‒Te bridges. alternation of Q4200 octahedra with cis and trans Again, this particular structure has Te mixed with bridging oxygen atoms, a type of variability that another cation (Fe3+) on all the octahedral sites, in does not occur with coordination numbers below order to give it an overall negative charge. 5. Note that all the corner-sharing zweier chains of Last, we consider the 26 structures of the present this study have trans bridging oxygen atoms. The study which contain both Te4+ and Te6+. Only one 4+ most complex chain is a loop-branched dreier Te3X12 of these structures (#675) has separate Te and isomer (Fig. 13i), which is made by polymerization Te 6+ polyhedra which are not linked by strong of the ‘double triangle’ cluster of Fig. 13d. bonds. In all the rest, ino, phyllo or tecto polymers The Te6+ polyhedra also link to form layers and contain Te in both valence states. Given their frameworks, but again, the range of polymer types different stereochemical preferences, Te4+ and Te6+ is restricted relative to that seen for Te4+.Q0603 are always ordered on distinct sites. The three types octahedra share edges to form TeX3 sheets with the of chains are all only zweier in backbone same topology as those of the Al(OH)3 poly- periodicity, but nevertheless, display other com- morphs, such as gibbsite (Saalfeld and Wedde, plexities. In Fig. 15a,Te4+ and Bi3+ are disordered 1974; Fig. 14a). However, the Te in these octahedra in pairs of edge-sharing Q0401 polyhedra, which are appears always to be in solid solution with another linked through Q2400 Te 6+ to make a chain of cation of lower valence (Fe3+,Ti4+,Mn4+ or Ge4+), ‘double triangles’. Figures 15b and c show chains which gives the layer an overall negative charge. in which Q2400 Te 6+ backbones are decorated by The same is true for the single case where a sheet is Q2200 Te 4+ to make 3-rings. Again, Cd demon- formed through edge-sharing of trigonal prisms, strates a tendency to be associated with structurally rather than octahedra (Fig. 14b). Such charge complex anions (cf. Fig. 10b and h). Figure 15d 2400 4+ 6+ reduction is not necessary when Q octahedra shows a relatively common type of Te Te X6 1400 4+ share corners to form TeX4 sheets with 4-rings layer (four examples known) in which Q Te (Fig. 14c). The most complex tellurate layer type and Q0600 Te 6+ share corners to 3- and 4-rings. has corner-sharing of Q2400 and Q4200 octahedra to Other isomeric layers with the same stoichiometry form a layer with overall stoichiometry Te3X14 are seen in Figs 13e‒g. The layer of Fig. 15e 2400 6+ (Fig. 14d), with the same topology as that seen in features zweier chains of Q Te O6. Unlike the 6+ chiolite, Na5(Al3F14) (Jacoboni et al., 1981). zweier Te chains of Fig. 13g, these strongly Long-range disorder is shown by Te6+ with zigzag chains are cis-bridged. They are linked lower-valence cations again in MTeO 4 tellurates through massicot-like chains (cf. Hill, 1985) of 0400 4+ with a monoclinically distorted (Te,M)X2 rutile Q Te O4, to form 3- and 5-rings; the 3-rings on framework, containg Q0062 octahedra (Fig. 14e). the Te6+ backbone form a loop-branched chain Here, disordered substitution with low-valence resembling that of Fig. 15c. The topologies of Figs cations results in electroneutrality of the frame- 15f and 15g both feature edge-sharing between Te6+ work. Further analogies between Te‒O and Al‒F octahedra to produce ‘double triangle’ clusters, but frameworks are provided by the rhombohedrally differ in coordination number of Te4+, numbers of 6+ distorted ReO3 structure of TeO3 itself (Fig. 14f ), non-bridging oxygen atoms on Te , and ring sizes collapsed so that the oxygen atoms approximate in the layers. Note that the positions of Te6+ and hexagonal close packing, which is shared with a Te 4+ in the ‘double triangles’ are reversed here, polymorph of AlF3 (Daniel et al., 1990), and the relative to the chain of Fig. 15a. Figure 15f has 1300 4+ 1501 6+ Te 2X7 framework of Fig. 14g, which is that of Q Te and Q Te with 8-rings between the 1400 4+ 0601 6+ weberite, Na2(MgAlF7) (Knop et al., 1982). The clusters, while Fig. 15g has Q Te ,Q Te 4+ 6+ weberite framework contains many 3- and 6-rings, and 4-rings. One compound, Ag2(Te Te O6), has similar to the pyrochlore framework of Fig. 12d, but three polymorphs ‘I’, ‘II’ and ‘III’, displaying, half of the octahedra are not Q0600, but are instead respectively, the topologies of Fig. 15f, d and g partly depolymerized to Q2400, which allows extra (#686, 684 and 687). The most popular type of anions to be included. The unique Te4X12 frame- mixed-valence layer, with seven examples, is the 4+ 6+ work of Fig. 14h also contains many 3- and 6-rings Te Te X7 topology of Fig. 15h. Here again, (as well as 4- and 8-rings), but there is also some zigzag cis-bridged chains of Te6+ (Q2400)are

444 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

4+ 6+ 4+ 6+ 4+ 6+ FIG. 16. Te‒O frameworks containing both Te and Te .(a) Framework of Te Te O5 (#696). (b)Te2 Te X8 in 4+ 6+ (#697 4+ 6+ 4+ 6+ (#698 , Ca(Te2 Te O8) ); (c)Te2 Te X8 in Sr(Te2 Te O8), viewed down chains of double triangles ); 4+ 6+ 4+ 6+ 4+ 6+ 4+ 6+ (d)Te2 Te 2 X11 in Ag2(Te2 Te 2 O11)(#699); (e) ordered pyrochlore framework Te3 Te X12 in Cs2(Te Te 3 O12) 4+ 6+ 4+ 6+ (#700); ( f ) sheared and depolymerized pyrochlore framework Te3 Te X12 in K2(Te Te 3 O12)(#701); 4+ 6+ 4+ 6+ #702 (g)Te2 Te 3 X14 framework in (Na1.6Ag0.4)(Te2 Te 3 O14), emphasizing kagome layers ( ); (h) modified pyrochlore 4+ 6+ 4+ 6+ framework Te3 Te 5 X23 of Rb4(Te3 Te 5 O23)(#703).

connected through Te4+ (Q2200), but the two All the mixed-valence framework compounds non-bridging ligands on both types of cation give have unique structures, although some of them are a greater X/Te ratio. The strong nonplanarity of the closely related to one another. In particular, most of layer and small O‒Te‒O angles allow four 6-rings them contain component layers with the well- to meet at each Te6+, in contrast to the three 6-rings known ‘hexagonal bronze’ or ‘kagome’ meeting at each node in the more familiar -type topology (O’Keeffe and Hyde, 1996), where 3- and layer (Fig. 11g). In Fig. 15i, a layer of stoichiometry 6-rings alternate around each node of the net in the 4+ 6+ 0400 4+ Te 3 Te X9 is formed by 6-rings of Q Te order 3.6.3.6. Figure 16a shows the framework of 0600 6+ 4+ 6+ linked through Q Te to make a sheet with Te Te O5, in which corner-sharing layers (similar additional 3- and 4-rings. to Fig. 14c)ofQ0600 Te 6+ are cross-linked via

445 A. G. CHRISTY ET AL.

corner-sharing massicot-like chains of Q0400 Te 4+; soro and cyclo tellurites), #1‒280. The various cross-linkage produces 3-rings, as so often is seen topologies that occur are summarized in Table 1 and 4+ 6+ in tellurate polymers. In carlfriesite, Ca(Te2 Te O8), depicted in Figs 4 and 8. Q2400 Te 6+ are cross-linked through edge-sharing dimers of Q0401 Te 4+ to make a trellis-like, 4+ nanoporous framework (Fig. 16b). The isomeric Structures with monomeric Te O3, no larger 4+ 6+ framework of Sr(Te2 Te O8) is also -like, structural unit, and no other anions or water but is formed by cross-linkage of chains similar to Structures #1‒24 are listed in Table 8 (deposited), those of Fig. 15a, made from ‘double-triangle’ along with their full references. In Li2[TeO3](#1), 0600 6+ clusters containing Q Te and edge-sharing helical columns of edge-sharing LiO4 tetrahedra || x 0501 4+ dimers of Q Te (Fig. 15c). Figure 16d shows are cross-linked into layers || (002), with TeO3 another rather open framework of stoichiometry pyramids bracing the layers. Layers are held 4+ 6+ 0500 4+ 0600 6+ Te 2 Te 2 X11, in which Q Te and Q Te together only through weak Te···O interactions define layers with a pseudohexagonal kagome net. across the interlayer. 6+ 6+ Te ‒O‒Te bridges link pairs of such layers, Na2[TeO3] and Ag2[TeO3](#2‒3) have a mono- producing ladder-like double chains of Te6+.Layer clinic √2×3√2 × 1 superstructure of the rocksalt pairs are, in turn, linked into a framework through type, with the Te coordination environment dis- pairs of edge-sharing Q0501 polyhedra. Kagome torted to give only three close neighbours. 4+ 6+ layers are also found in the Te3 Te X12 framework Tl2[TeO3](#4) has an orthorhombic 3 × 2 × 1 of Fig. 16e, which is that of pyrochlore and, thus, superstructure of rocksalt with a different cation contains kagome nets in four different orientations. ordering pattern. Short bonds form ‒Te‒O‒Tl‒O‒ The framework, ideally cubic in symmetry, is Tl‒O‒ chains || x, with a crankshaft shape rhombohedrally distorted as a result of Te4+‒Te 6+ reminiscent of the Pb‒O chains in the massicot ordering. Like Fig. 12d, this is a rare example of form of PbO; such chains recur frequently in the Te 4+ in octahedral coordination, with no evidence structures of the present study, as noted above. Both of a stereoactive lone pair: all Te cations are Q0600. Tl and Te have stereoactive lone pairs and only The K analogue of the Cs compound of Fig. 16e has three close oxygen neighbours, making the struc- the modified pyrochlore framework shown in ture strongly layered || (020). AgTl[TeO3](#5) has Fig. 16f. Monoclinic shear of the structure is similar cell dimensions but a different cation accompanied by breaking of some Te4+‒O‒Te 6+ ordering pattern and . Again, the links, so that Te4+ is now Q0500 (with a stereoactive structure is layered, but this time || (200). 6+ 2400 lone pair) and one-sixth of the Te are Q . K2[TeO3] and Cs2[TeO3](#6‒7) have nearly- Kagome nets are also a major feature of the identical structures that are both oxygen-stuffed 4+ 6+ Te 2 Te 3 X14 framework in Fig. 14g, where the derivatives of the Ni2In type; they are therefore 0600 6+ 2– Q Te form such layers, which are cross-linked TeO 3 analogues of the high-temperature K2SO4 via pairs of edge-sharing Q5001 Te 4+. As for the structure (O’Keeffe and Hyde, 1985). The alkali framework of Fig. 16d, the cross-linkage produces cations are in 6‒9 coordination. Rb2[TeO3](#8) additional 3- and 4-rings. The orthorhombic appears to have a slight monoclinic distortion of the 4+ 6+ Te 3 Te 5 X23 framework is yet another modification same structure, although the refinement is of poor of the pyrochlore type, in which the lone pairs of Te4+ quality. 4+ 4+ are accommodated by breaking some Te ‒O‒Te Ca[TeO3] and Sr[TeO3] both occur in a large 1 links, with complete elimination of /24 of the number of polymorphs with large unit cells and low oxygens. The ordering pattern of Te4+ and Te6+ is symmetry (#9‒15). All structures are packings of quite different from those of Figs 16d and 16e. (Ca,Sr)O6–8 polyhedra containing tunnels, with Kagome layers are preserved in two orientations, TeO 3 groups bracing the sides and the tunnels and but are not exclusively Q0600 Te 6+: alternate layers lone pairs pointing into the central space. The two 1 1 0500 4+ have /6 or /3 of their cations Q Te . forms of Ba[TeO3] are quite different. One of them (#16) has the simple monoclinic structure of KClO3 (Bats, 1978); the Ba and Te substructure resembles Descriptions of individual structures the CrB/TlI type (Helmholtz, 1936), and Ba is in Finite Te4+–O complexes 7 + 2 coordination by oxygen. BaTeO3 is thus an oxygen-stuffed analogue of TlI, in the same way Our descriptions of individual structures begin with that , BaSO4, is an oxygen-stuffed derivative those that contain finite Te4+‒O complexes (neso, of the closely related FeB structure (O’Keeffe and

446 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

Hyde, 1985). The other dimorph (#17) has an derived by oxygen-stuffing of a different but approximately cubic close-packed (ccp) array of equally simple hexagonal arrangement of cations. Ba + Te but a very complex ordering pattern, with MgTeO3 ·6H2O ≡ [Mg(H2O)6][TeO3](#29) has Ba in 8‒10 coordination. a rhombohedral structure with angle αrh = 97.4°. It There are also two synthetic polymorphs with can be regarded as a derivative of the CsCl type, in + – known structures for Pb[TeO3]; interestingly, these which Cs and Cl anions are replaced by 2+ 2– appear to be distinct from the two mineral species [Mg(H2O)6] and [TeO3] complexes. As the of this composition, triclinic fairbankite (Williams, lone pairs of the Te cations all point in the same 1979) and orthorhombic plumbotellurite direction along z, the structure is polar and (Spiridonov and Tananeyva, 1982), both of which ferroelectric, with point group R3. The structure remain poorly characterized. The tetragonal form of Sr[TeO3]·H2O(#30) is centrosymmetric but (#18) has a structure very similar to that of scheelite strongly anisotropic, with edge-sharing SrO6(H2O) (CaWO4) but with ¼ of the oxygens removed in an polyhedra defining layers || (100). The layers are ordered fashion. The coordination numbers are 6 held together via H-bonds and Te lone-pair/ and 3 for Pb and Te, as opposed to 8 and 4 for Ca secondary bonding interactions. Ba[TeO3]·H2O and W. The lone pairs of both Pb2+ and Te4+ are (#31) is isostructural, although with x and z directed into tunnels running || z. The more complex directions exchanged. 2+ monoclinic structure of #19 has a framework of The structures of A3 [TeO3]2X2 (A = Sr or Ba; PbO4–6 and TeO3, again with tunnels (this time || y) X = Cl or Br) have a large (a ≈ 16 Å) cubic unit cell which act as micelles to contain the lone pairs. with the same space group Fd3m as diamond (#32‒ 4+ Cd[TeO3](#20) has Te filling interstices in an 34). Clusters [Sr6Te 4O12] can be distinguished, in edge-sharing framework of irregular CdO6 polyhe- which Sr are at the vertices of an octahedron, linked dra. Sc2[TeO3]3 (#21) has edge-sharing layers of by O along the octahedral edges, and braced by Te ScO6–7 polyhedra || (020), which are bridged by Te. above four out of the eight octahedral faces. These 4+ In Ce [TeO3]2 (#22), zigzag chains of edge- clusters are arranged in the same fashion as the C sharing CeO8 are linked into a framework by Te. atoms of diamond, and Sr3 triangles of neighbour- The Th and Pu analogues (#23‒24) are isostructural. ing clusters face each other to define a second type of octahedron between them. Halide anions centre both types of octahedron, and also occur in the 4+ Structures with monomeric Te O3 and no largest remaining interstices of the structure with larger structural unit, but with additional six Sr arranged in an almost planar at 3.6‒ anions or water 4.4 Å and six Te above and below the plane at 3.3‒ Structures #25‒46 are listed in Table 9 (deposited), 3.8 Å. The structure can be regarded as a derivative along with their full references. In Li3[TeO3](OH) of the pyrochlore type, with X replacing CN8 and (#25), LiO3OH tetrahedra and TeO3 pyramids form CN6 cations of pyrochlore and A replacing the honeycomb-like double layers || (100), which are framework anions of pyrochlore. Pb3[TeO3]Cl4 held together only by long Te···O and lone-pair (#35) is quite different, in that one tellurate interactions. Thus, the structure resembles that of oxygen is tetrahedrally coordinated OTePb3 and the chemically similar but anhydrous phase #1. the others triangularly coordinated OTePb2 to make 4+ Na2[TeO3]·5H2O(#26) has three types of Na. a rod [Pb3TeO 4] running || z. The rod has a Face-sharing trimers (H2O)2Na1 ≡ (H2O)3 ≡ rhombic cross-section with the Pb cations (bonded Na2 ≡ (H2O)3 ≡ Na1(H2O)2 share corners with to only 2 or 3 oxygen atoms) on the exterior, and are each other and with square-planar Na3(H2O)2O2 arranged in a herringbone fashion. They are held to form a very open hydrogen-bonded framework in together through four crystallographically distinct which TeO3 is only loosely held. KNa[TeO3]· Cl anions, bonded to 3‒5 Pb. Again, the structure is 3H2O(#27) has a denser, simpler structure with polar due to tilt of all TeO3 groups in the same sense K(H2O)6O3 and Na(H2O)3O3 polyehdra sharing along the z direction. 3+ faces. The arrangement of K, Na and Te is a In Ho[TeO3]Cl (#36), Ho is in pentagonal threefold ordering of the primitive hexagonal net, bipyramidal coordination by five O and two Cl (one so this can be regarded as an O/H2O-stuffed apical and one equatorial). The HoO5Cl2 polyhedra derivative of that archetype. The same is also true form edge-sharing ribbons || y, which are again of K2[TeO3]·3H2O(#28), although the oxygen arranged in herringbone fashion but are cross-liked positions there are adjusted to give 8‒13 coordin- through Te cations. The lone pairs of Te point into ation. Note that the anhydrous analogue (#6)is well-defined micellar channels that run || y, between

447 A. G. CHRISTY ET AL.

FIG. 17. Examples of structures with monomeric TeO3 pyramids that are either weakly bound, or are part of larger structural units that are finite clusters or chains (Tables 9‒10, deposited). Small spheres: O (dark pink), when not part of a polyhedron. Medium spheres: Cl (light green). Large spheres: K (purple), rare-earth cations Nd, Dy or Yb (light yellow). Polyhedra: Cu (cyan), Ni (light green), Mo or W (grey) and Te (dark green).

the ribbons. Nd5[TeO3]2O4Cl3 (#37) has three types along the x direction. Oxygen atoms define nearly- 3+ of Nd polyhedra: NdO8 , irregular NdO6Cl cubic LuO8 polyhedra which share edges to form and NdO5Cl3 square antiprisms. These form thick sheets || (100). Some oxygen atoms are in – layers || (001), with Cl bridging the interlayer tetrahedral coordination (OLu2NaTe), while others regions and Te bracing the outsides of the layers. are displaced away to tetrahedral sites so as to be in The TeO3 group is canted so that Te makes four nearly plane triangular coordination by Lu2Te, with long bonds to Cl at 3.19‒3.40 Å (Fig. 17). a second Te much more distant at 3.15 Å. Thus, the Na2Lu3[TeO3]4I3 (#38) has all the atoms except O structure can be regarded as a modified superstruc- in an approximately ccp array, with a layer ture of the fluorite type (the cell parameters sequence (Na2Te 4), Lu6, (Na2Te 4), I6 alternating correspond to 2 × 1 × 3 fluorite cubes).

448 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

Alternatively, it may be described as a structure in of these channels, and the channels act as micelles 4+ – – which thick Lu‒O sheets are braced by Te , with I which contain the Te lone pairs and also NO3 anions. occupying the interlayer region and NaO4I4 square The structure is thus strongly reminiscent of the 1+ antiprisms holding the sheets together. Nd4Cu nitrate-free tellurites #9‒15.Ca5[TeO3]4(NO3)2 · [TeO3]5Cl3 (#39) has a superficially similar 2H2O(#43) is rather similar, but the Ca layers stoichiometry but a quite different structure. || (200) remain completely separate, with no bridges NdO8, NdO7Cl and NdO7 polyhedra share edges connecting them. Tellurium lone pairs and nitrate to form walls that surround two types of channel groups point into continuous interlayer gaps. running || y; large and small channels alternate in a Sc2[TeO3](SeO3)(SeO4)(#44) has zigzag chains checkerboard fashion. The small channels contain of edge-sharing ScO7 polyhedra running || x.TeO3 one out of five distinct types of TeO3, which again groups connect the chains into pairs, and the SeO3 render the structure polar by all pointing in the same pyramids connect these further into layers || (002), sense along the y direction. The large channels are while SeO4 tetrahedra share oxygens with four lined by the rest of the Te atoms, but still contain different Sc to link the layers into a rather open enough space to accommodate a zigzag corner- framework. 4– sharing chain [Cu2Cl6] of CuCl4 tetrahedra, held La2[Si6O13][TeO3]2 (#45) contains LaO9 and in place by Nd3‒Cl3 links as well as each Cl TeO 3 polyhedra, forming layers || (100). These making two to four long bonds to Te. Bi2[TeO3]2O intercalate with a silicate sheet in which dreier (#40) has a defect fluorite superstructure (cf. #38) double chains like those of okenite (Merlino, 1983) with a unit cell corresponding to 4 × 1 × 4 cubes of link to their neighbours to make a double layer in a 1 4 fluorite, with /8 of the anions missing. Overall, Bi disordered fashion, such that ⅔ of the Si are Q and 3 2– + Te form a ccp array. They are ordered into ⅓ are Q , giving an overall composition [Si6O13] . columns || y, with 1 × 1 and rectangular 2 × 3 blocks A similar intercalation of La‒Te and silicate of Bi separating 2 × 1 and paralleogram-shaped 2 × sheets occurs in the triclinic structure of La4[Si5.2 3 blocks of Te. If tetrahedral interstices are Ge2.8O18][TeO3]4 (#46) but here, the layers are || 3+ surrounded by Bi4, then they are occupied by (010), La cations have CN8‒10, and the silicate‒ O. Bi2Te 2 tetrahedra have oxygens displaced away germanate anion is a loop-branched single sheet from one Te or absent, BiTe3 tetrahedra have which is formed by cross-linking of narsarsukite- oxygens linked only to 1 Bi + 1 Te, and Te4 like tubes (Peacor and Buerger, 1962) running || x. tetrahedra are unoccupied. Tellurium lone pairs Half of the (Si,Ge) are Q3 and half are Q4, and Ge > point along ±y for the small Te blocks, but are Si in two out of the eight tetrahedral sites. directed into the interiors of the large blocks, which along with long Bi‒O bonds mark the gap between 4+ weakly defined thick layers || (200). Te2 in this Structures with monomeric Te O3 as part of a structure is our unique example of ‘2-coordinate’ larger structural unit that is a finite cluster. Te; however, if all Te‒O distances out to 3.5 Å are Details for structures #47‒62 are shown in Table 10 considered, a square-pyramidal coordination poly- (deposited). HgTeO3 ≡ [Hg2(TeO3)2](#47) has two hedron (Fig. 3e) is defined by oxygens at 1.865, types of Hg in quite differently distorted coordin- 1.911, 2.519, 2.793 and 3.062 Å. It is possible that ation polyhedra. Hg1 has two oxygen nearest the O coordinates are not accurate in this structure, neighbours at 2.06‒2.12 Å and four more oxygen and that the true coordination polyhedron has a atoms at 2.54‒2.73 Å, while Hg2 has one close narrower spread of bond distances. Smirnite, oxygen neighbour at 2.14 Å, one at 2.30 Å and Bi2[TeO3]O2 (#41) has yet another defect fluorite three more at 2.40‒2.46 Å. Using the parameters of superstructure with a unit cell corresponding to 2 × Brese and O’Keeffe (1991), the Hg2 distances 1 3 × 1 fluorite cubes with /6 of the anions missing, correspond to bond valences of 0.57, 0.37 and and many of the rest displaced so as to approximate 0.28‒0.24 vu, so a ‘strong bond’ threshold of 0.3 vu plane triangular coordination by 3Bi or 2Bi + 1Te. would make both Hg atoms 2-coordinate, with O‒ The Te atoms are on the outsides of thick layers Hg2‒O less symmetrical and less linear than O‒ || (100), which are linked only through long Bi…O Hg1‒O. The strong bonds define a structural unit and Te…O bonds. that is a neutral molecule in which Hg1 and Hg2 In Ca6[TeO3]5(NO3)2 (#42), CaO6–8 polyhedra form a ring with two TeO3 groups. These molecules share edges to form undulating layers || (100) and also lie in layers || (002) and are linked through long bridge these layers into a framework which contains Hg…O and Te…O bonds. The complex structure of 5+ 4+ large channels || y.TeO3 pyramids decorate the sides Cd4V2 Te 3 O15 ≡ Cd4[VO3][(VO3)(TeO3)](TeO3)2

449 A. G. CHRISTY ET AL.

(#48) contains several structure-building elements. 11.2H2O (#55) have extremely complex hetero- 2– Pyroxene-like zigzag vanadate chains [V2O6] run polyanions which can be derived from incomplete || x, although these do not contain Te. The most fragments of the cuboctahedral TM12O40 Keggin complex structural unit with Te is a cluster ion (Keggin, 1934), where T = a tetrahedral cation 3– 3– [VTeO6] formed by corner-sharing of a VO4 and M = an octahedral cation. The ion is composed 2– tetrahedron and a TeO3 pyramid. The V-bearing of two dissimilar half-cuboctahedral fragments of structural units act as bridges between layers || (020) the Keggin cage. One fragment has composition of relatively weakly-bound CdO6–8 polyhedra. The [W9O30(TeO3)], and has a TeO3 pyramid rather than 2– remaining TeO3 are attached to the Cd‒O layers, a TO4 tetrahedron bracing a bowl-shaped cluster of and all Te lone pairs point into channels than run || WO6 octahedra (Fig. 17). The other fragment is x, between the vanadate chains. [W6Mo3S4O26(H2O,Cl)3]. It has no analogue of the 2+ 4+ 6+ 6+ In Pb2[Pd Cl2(TeO3)2](#49), two TeO3 central Te cation, and has Mo rather than W groups are linked through a PdO2Cl2 square to as the cations on one triangular face of the cage. 4– make an anionic complex trans-[PdCl2(TeO3)2] . The four anions bonded to two to three Mo and no These complexes form layers || (002) which are WareS2– rather than O2–, and the three anions linked via irregular PbO5 polyhedra, with the long bonded to one Mo only are (H2O,Cl). The two half- axes of complexes oriented towards [120] and cuboctahedra link through six oxygen atoms to  [120] in alternate layers. Bi2WTe2O10 ≡ form an ellipsoidal cluster that is similar but not Bi2[WO4(TeO3)2](#50) has two TeO3 groups identical to the Wells‒Dawson cluster (Wells, 1947; linked through a WO6 octahedron to make a Dawson, 1953; Baker and Figgis, 1970). The 6– complex cis-[WO4(TeO3)2] . These V-shaped clusters are held together by additional water anions are linked through irregularly coordinated molecules and Cs+ and Na+ cations in a wide Bi3+ cations. The six shortest Bi‒O bonds out to range of coordination states. 2.58 Å define edge-sharing chains of distorted The heteropolyanion in K8Na2[Pd3(W9TeO 33)2]· BiO6 octahedra || y, which with the Te‒W anions 51H2O(#56) consists of two half-Keggin subunits make layers || (200). However, longer Bi‒Oat linked into a single, large dumbell-shaped anion 2.83 and 3.27 Å link the Bi chains into through a set of three square-planar coordinated continuous sheets || (002), alternating with Pd2+ cations, to make an expanded version of the layers of Te‒W anions. The cluster anion in cluster in #54‒55. These anions are packed around Nd2W2Te 2O13 ≡ Nd2[W2O7(TeO3)2](#51) has inverse tetrad axes and linked through K(H2O)7–9 two TeO3 linked to an edge-sharing pair of and Na(H2O)6 polyhedra. K9Na[Cu3(H2O)3 octahedra, W2O10. However, while Te1 is joined (W9TeO 33)2] · 16H2O·(#57) is almost isostruc- to both W atoms to form a 3-ring of cation- tural but has a much lower water content, and 2+ centred polyhedra, Te2 is attached only to W1, each of the bridging Cu also has an H2O 6– giving the overall stoichiometry [W2O7(TeO3)2] . molecule associated, to give it 5-fold rather than These anions lie in layers || (102), and are 4-fold coordination. Unusually, water molecules connected through CN8‒9Nd3+. are included in the structural unit here and in the K4[Mo6Te 2O24]·6H2O(#52) and its isostruc- clusters below, when they are necessary to fully tural Rb analogue (#53) are our first examples of a define the coordination environment of a cluster large family of salts (mainly telluropolymolyb- cation. dates) in which the structural unit is a modified [N(CH3)4]2Na6[Ni(H2O)2(Ni(H2O)3)2(WO2) Anderson‒Evans anion (Anderson, 1937; Evans, (W9TeO 33)2] · 23H2O(#58) and its analogue with 2+ 2+ 1948, 1974). Six MoO6 octahedra share edges to Zn replacing Ni (#59) have slightly more form a hexagonal ring, but instead of one Te complex clusters in which the W9TeO 33 fragments occupying the vacant octahedral site at the ring are not half-cuboctahedra but half-anticubocta- centre, two pyramidally coordinated Te sit above hedra, in which two square faces share an edge 2+ and below the vacant octahedral position. The (Fig. 17). These are linked through two M O3(H2O)3 hexagonal heteropolyanions lie in layers parallel to octahedra and two octahedra that are 50%   2+ 6+ (102), with their planes normal to either [111] or M O4(H2O)2 and 50% W O6. There is also a  5+ 6+ [111] directions. Water molecules and 8‒9 coordi- partially disordered cluster in K14[V12Mo12 nated alkali cations lie between them (Fig. 17). O69(TeO3)2] · 27H2O(#60), in which two half- Cs6Na2[W6Mo3S4O20(H2O)3(W9TeO 33)]·11.7 Keggin units each have an average composition H2O(#54) and the nearly isostructural V4.5Mo4.5TeO 33 and are linked through a ring of Cs7.15Na1.85[W6Mo3S4O20(H2O)2Cl(W9TeO 33)] · three VO4 tetrahedra alternating with three MoO6

450 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

FIG. 18. Examples of structures with monomeric TeO3 pyramids as part of larger structural units that are chains or layers (Tables 10‒11, deposited). Small spheres: H (pale pink). Medium spheres: O (dark pink), when not part of a polyhedron. Large spheres: Bi (pale violet), Ca (orange), Na (dark yellow), Sr (red) and Yb (light yellow). Polyhedra: As (brown-green), Cu (cyan), Ga (light green), Te (dark green) and V (blue).

octahedra. K10[V4(V3Mo17)O74](TeO3)] · 15H2O instead of a TeO3 pyramid. Instead of the two (#61) has a unique cluster that contains two ‘bowls’ facing towards each other, the vanadate different kinds of half-Keggin unit. One is bowl is inverted, so that the VO4 tetrahedron is (V3Mo5)TeO33 with partial V‒Mo disorder; this pointing away from the centre of the cluster. The has the same topology as the half-Keggin units of two bowls are linked through a ring of alternating V #54‒57 and #60, with CN3 oxygen atoms centring and Mo, as for #60. The extraordinarily complex 4+ 3+ the three triangular faces around the sides of the structural unit of (NH4)[H(Ru4 O6(H2O)9)2(Fe ‘bowl’ but not the bottom triangular face. The other (H2O)2)2(W9TeO 33)2] · 36H2O(#62) has two half- half-Keggin unit is Mo9VO35, of the type found in anticuboctahedra W9TeO 33 similar to those of #58‒ the Wells‒Dawson cluster, in which it is the bottom 59, linked through a pair of FeO4(H2O)2 octahedra face that is centred, and with a VO4 tetrahedron and also through three oxygen atoms each of two

451 A. G. CHRISTY ET AL. tetrahedral clusters or corner-sharing RuX6 octahe- polymorph has a layered structure (#221, below). dra, Ru4O9(H2O)9. Sr3(UO2)(TeO3)4 ≡ Sr3[(UO2)(TeO3)2](TeO3)2 (#71) has similar chains || y, all sharing a common attitude, and bridging layers || (200) of SrO7–8 4+ Structures with monomeric Te O3 as part of a polyhedra. Additional isolated TeO3 brace the Sr larger structural unit that is a chain layers. The complex chain in Yb2[Cu3Cl4(TeO3)4] The next 11 structures (#63‒73, Table 10, depos- (#72) is again based on linked 4-rings, but the ited) have TeO3 groups incorporated into infinite polyhedra are CuO6 octahedra at the nodes and heteropolymeric anions. In magnolite, [(Hg2) CuO3Cl2 on the loops. One of two types of TeO3 (TeO3)] (#63), each Hg atom is bonded to one acts as an additional bridge between two Cu, 2+ other at 2.53 Å to make a (Hg2) dimer, and has no making Cu2Te 3-rings, while the other type of TeO3 other neighbours apart from one close oxygen at shares an edge with CuO6, so that the bridging 2.06 Å and three more distant at 2.69‒3.00 Å. The oxygens in the Cu chain have CN3. These chains Hg dimers and TeO3 groups form continuous run || x and are linked through edge-sharing zigzag chains ‒O‒Te‒O‒Hg‒Hg‒O‒Te‒O‒ running || y chains of YbO8 to make thick layers || (001) and zigzagging in the (001) plane, with Te atoms at (Fig. 18). The layers are held together only by long the apices of the bends. The chains are held together bonds to Te. Bi2W3Te 2O16 ≡ Bi2[W3O10(TeO3)2] … … only by long Hg O and Te O bonds. BaZn(TeO3) (#73) again has loop-branched chains of 4-rings, Cl2 (#64), better written for our our purposes as but the polyhedra are all WO6, giving a chain Ba2[Zn2Cl3(TeO3)2]Cl, has double chains || y stoichiometry W3O14.TeO3 groups share non- resembling those of the minerals, in bridging oxygen atoms to make W2Te 3-rings, which TeO3 pyramids instead of tetrahedra alternate similar to the Cu2Te of #72, and giving a final chain 3 2 with Q ZnO3Cl tetrahedra and Q ZnO2Cl2. The composition W3Te 2O16. The chains run || y and lie chains lie in double layers || (002) with additional in layers || (002), which cross-link sheets of BiO8 Cl– and 6‒7 coordinate Ba2+ between them. Dy polyhedra. [CuCl(TeO3)2] and its analogues (#65‒67)havea loop-branched structural unit, in which TeO3 4+ pyramids and CuO4Cl pyramids make CuTeCuTe Structures with monomeric Te O3 as part of a 4-rings, which link into a chain || x through the Cu larger structural unit that is a layer atoms (Fig. 17). The chains form layers || (002), Structures #74‒#112 (Table 11, deposited) have which are interconnected through zigzag chains of infinite two-dimensional structural units. [Cu(NH3) edge-sharing DyO8. The Te lone pairs and Cl are (TeO3)](H2O) (#74) has a 3-connected net with 4- located in channels which run between the Dy chains and 8-rings, topologically similar to the ‘apophyl- 2 and the Cu‒Te chains. The compound Yb3[Cu lite’ layer of mackayite (Fig. 11i), but the polyhedra + 1+ Cl2(TeO3)2]2[Cu Cl2](#68) has an open-branched at the nodes are alternately TeO3 and square-planar 2+ chain || y in which pyramids Cu O3Cl2 and TeO3 CuO3(NH3) (Fig. 18). The polyhedra are tilted so alternate along the chain backbone, while a second that a very elongated octahedron around Cu is type of TeO3 acts as a branch sharing an oxygen atom completed by another TeO3 oxygen at 2.60 Å and with the Cu. These chains attach on either side of a the H2O molecule at 3.07 Å. The layers are || (200), layer || (100) of edge-sharing YbO8 polyhedra, with and are connected only through H bonds. 1+ – isolated, linear [Cu Cl2] anions in the interlayer Bi[Cu3O2(TeO3)3]Cl (#75) has a complex layer in gap (Fig. 17). LaNbTeO6 ≡ La[NbO3(TeO3)] (#69) which a hexagonal honeycomb array of CN3 has NbO6 octahedra sharing trans corners to make oxygen atoms are linked through the two bridging zweier chains || y; oxygen atoms are shared with Te so oxygen atoms of CuO4 . The layer is as to make two differently oriented Nb2Te 3-rings, corrugated because one type of Cu has trans which alternate along the chain. Chains are held bridging oxygen atoms while the other type has together via long Te…O bonds and 8-coordinated cis. A Te atom sits above or below each CN3 La3+. This compound is isostructural with oxygen, sharing its own oxygens with two trans Cu Pb[MoO3(SeO3)] (Oh et al., 2012). and one cis Cu. Elongated octahedra around all Cu Tl2[(UO2)(TeO3)2]-β (#70) has Te‒U‒Te‒U are completed by long bonds to Cl. The layers are || 4-rings which link through UO6 octahedra to (002) and are connected through BiO8 polyhedra make loop-branched chains || x. These pack in a and long Te…O bonds (Fig. 18). Juabite, herringbone fashion, and are linked through Ca[Cu10(AsO4)4(TeO3)4(OH)2]·4H2O(#76) has ribbons of edge-sharing TlO5–7 polyhedra. The α a structure in which double layers || (010) are held

452 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

FIG. 19. Examples of structures with monomeric TeO3 pyramids as part of larger structural units that are layers (Table 11, deposited). Small spheres: H (pale pink). Large spheres: Cl (yellow-green) and Li (pale blue). Polyhedra: Al (pale grey), Fe (orange-brown), In (pale blue), Ni (bright green), S (yellow), Te (dark green) and V (blue).

… together only through long Te O bonds. The two polyhedra share corners with TeO3 to make chains sublayers contain edge-sharing blocks OTe = Cu = ‒V1‒V2‒Te‒V1‒V2‒Te‒ running || z and zigzag-  O2 =Cu=O2 = TeO with long axes || [101], which ging in the (100) plane. Such chains at two different are held together by sharing corners with conti- heights along x are linked by edge-sharing of VO5 nuous chains of more CuO4 squares and AsO4 polyhedra to make a layer || (200) which is strongly tetrahedra (Fig. 18). The resulting net is approxi- corrugated but not topologically a double layer. Thus, mately centred-rectangular, and has 8- and 3-rings. the TeO3 groups and can be regarded as linking Two such sheets are linked by the inward-pointing [V4O14] tetramers (Fig. 18). One oxygen atom of apical oxygens of AsO4 tetrahedra connecting to TeO 3 is directed at the interlayer gap, while the lone additional Cu2O4(OH)2 dimers. Loosely bound pair points into a deep fold in the layer. Water 2+ 2+ H2O and CN6 Ca lie between the two sublayers. molecules and CN8 Sr are between the layers. 5+ Sr2V4 Te 2O16 ·H2O ≡ Sr2[V2O5(TeO3)]2 ·H2O In Na[Ga(TeO3)2](#78), edge-sharing pairs of (#77) has a structure in which CN5 V1 and CN4 V2 GaO6 octahedra are linked through corner-sharing

453 A. G. CHRISTY ET AL.

TeO 3 to make layers || (002) consisting exclusively the raspite structure in #650, below. The β of Ga‒Te‒Ga‒Te 4-rings. A second type of TeO3 polymorph of VTeO4 has a very different, layered shares the remaining oxygen atoms of the Ga structure (#222, below). octahedra, forming Ga‒Te‒Ga 3-ring loops, which [InCl(TeO3)] (#83) and its Br analogue (#84) occur in pairs to make a Ga2Te 2 unit resembling the have edge-sharing chains of InO4X2 octahedra (X = ‘double triangle’ tetrameric Te unit that occurs in Cl or Br) running || z, sharing oxygen atoms with many Te-only polymers (Figs 10f,10h,13d,13i, TeO 3 groups to make In2Te 3-rings. The resulting 15f,15g and 16c). Layers are linked through CN7 loop-branched chains (similar in topology to the Te + 3+ Na ions (Fig. 18). Na[Fe (TeO3)2](#79)is chain of Fig. 15c), at two different x heights, are 3+ isostructural. , Fe2 Te 4O9(OH)3Cl linked through the third oxygen ligand of Te to ≡ [Fe2(TeO2OH)3(TeO3)]Cl (#80) also has Fe2Te 2 make a corrugated layer || (100), with layers … ‘double triangles’. These share FeO6 edges to form connected only via long Te X interactions zigzag chains || x, which are cross-linked via a (Fig. 19). [BiI(TeO3)] (#85) has the same space – second type of TeX3 into layers || (001). The Cl lie group and similar unit-cell parameters, but is not between the layers, and are weakly bonded to Te quite isostructural. The TeO3 groups are differently (Fig. 19). Oxygen atoms that are not bonded to Fe oriented, so that they cross-link chains at the same x are 100% OH– for Te1, 50% O2– 50% OH– for Te2 coordinate, and the structural unit can be described 2+ 3+ (Kampf and Mills, 2011). [(Fe Fe4 )(TeO3)6]Cl2 as a double layer rather than a highly corrugated (#81) has three types of Fe polyhedra. (Fe1)O6 single layer. The Bi coordination polyhedra are octahedra share two trans corners with (Fe3)O5. BiO5I2 rather than octahedra, and share corners along (Fe2)O6, share two edges with each other to make the chain direction z rather than edges, while making zigzag chains || x, and a third edge with Fe3, linking new shared-edge connections between sublayers.  5+ all Fe polyhedra into an undulating layer || (011) YV Te 2O8 ≡ Y[VO2(TeO3)](TeO3)(#86) has with elongated 12-rings. The mean Fe‒O distances two topological types of TeO3. The first type (Te2 are very similar for Fe1 and Fe2 (2.03 vs. 2.01 Å), and Te3) share corners with VO6 distorted 2+ implying that there is little ordering of Fe and octahedra to complete V2Te 3-rings above and 3+ Fe . Two types of TeO3 share all oxygen atoms below a corner-sharing VO4 layer with a square-net with Fe polyhedra, with lone pairs pointing into the topology similar to those of Fig. 11a,f. Layers are || – interlayer space. As in rodalquilarite, interlayer Cl (002), and connect through TeO3 sharing oxygen are weakly bonded to Te. atoms with edge-sharing sheets of YO8 polyhedra. 4+ The phase α-V TeO 4 ≡ [VO(TeO3)] (#82)is The remaining Te1 and Te4 act as additional braces isopuntal with the raspite polymorph of PbWO4 on the Y layer, and are not part of the larger (Fujita et al., 1977). Edge-sharing, distorted VO6 structural unit. 6+ octahedra form V2O8 chains || y, analogous to the BaMo2 TeO 9 ≡ Ba[Mo2O6(TeO3)] (#87) has W2O8 chains of raspite. These are arranged MoO6 octahedra sharing corners to form zigzag similarly to the corresponding chains in ferberite, zweier double chains || y, which are cross-linked via FeWO4 (Ulku, 1967) but with an additional lattice TeO 3 into double layers || (002). BaO10–11 poly- 5+ 5+ shear so that (1) the anions no longer form a hedra lie between the layers. LiV3 Te 2O12 ≡ Li[(V continuous hexagonal close-packed substructure, O2)3(TeO3)2](#88) has strips of distorted VO6 and (2) the Pb/Te polyhedra are no longer octahedra sharing edges and CN3 oxygen atoms to octahedra, but are very irregular (Fig. 19). The form chains || z similar to the Te chain of Fig. 10a. structure can be regarded as a distortion of the Te1 shares three oxygen atoms with three Vof one pucherite type, which is orthorhombic and has an such chain, making clusters which include a Te2V2 anion array that is still hexagonal close-packed (see ‘double triangle’ motif, while Te2 shares oxygen discussion of #648–650 below). In raspite, Pb2+ has ligands with V atoms of two chains, to link them seven neighbours at 2.3–2.9 Å and no more within into a double layer || (010). CN6 Li+ cations sit 3.2 Å, while TeVO4 shows even less regularity: within corrugations of the layer, and layers are held Te 4+ has three strongly bound neighbours at 1.75, together through weak Li‒O and Te‒O bonds 4+ 5+ 4+ 5+ 2.00 and 2.25 Å, followed by four more within (Fig. 19). (NH4)V V TeO 7 ≡ (NH4)[(V O)V 3.4 Å, at 2.42, 2.59, 3.04 and 3.17 Å. As is typical O3(TeO3)] (#89) has extremely corrugated layers 4+ 4+ for V , there is one very short bond of 1.73 Å of || (200) in which alternating V O6 octahedra and 5+ one of the oxygen atoms that is not linked to Te, V O4 tetrahedra each share three corners to form although this ligand is also only 2.04 Å from a 6-rings. TeO3 shares the otherwise non-bridging second Vatom. Note that Te6+ plays the V/W role in oxygen ligand of V5+ and two of V4+; the additional

454 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

FIG. 20. Examples of structures with monomeric TeO3 pyramids that are part of larger structural units that are layers (Table 11, deposited). Large spheres: Ag (pale grey), Cs (blue), K (purple) and Pb (dark grey). Polyhedra: Co (magenta), Mo or W (dark grey), Te (dark green), U (yellow) and Zn (pale grey).

connectivity means that the structural unit can be to x through TeO3. There are four such layers per regarded as a double layer. The remaining ligand of unit cell, which alternate in their facing direction. V4+ is very close (1.61 Å), making a well-defined The apical oxygen atoms of V polyhedra point 2+ + + vanadyl group, [V = O] . (NH4) ions are in the towards interlayers that contain Cs ions only, while 4+ 5+ interlayer gap. Cs3[(V O)V O3(TeO3)]2Cl (#90) Te lone pairs point towards another type of has a closely related structure with similar unit-cell interlayer, which contains both Cs+ and Cl–. 4+ 5+ dimensions, in which chains (V V O8)||z of [Al2(TeO3)(SO4)(OH)2](#91) has zigzag edge- 4+ 5+ alternating V O6 and V O4 do not form continu- sharing ribbons of AlX6 octahedra || z, which in turn ous layers, but are linked into a single layer normal share corners with each other to make continuous

455 A. G. CHRISTY ET AL.

FIG. 21. Examples of structures with monomeric TeO3 pyramids that are part of larger structural units that are frameworks (Table 12, deposited). Small spheres: H (pale pink) and O (dark pink), when not part of a polyhedron. Large spheres: K (purple) and Pb (dark grey). Polyhedra: Cu (cyan), Ga (pale green), Mo (dark grey) and Te (dark green).

sheets Al2O5(OH)2 || (100). The sheets are braced [ZnZnBr2(TeO3)] and [CoCoBr2(TeO3)] (#97‒ by SO4 tetrahedra sharing two oxygen atoms and 101) have an orthorhombic structure in which TeO 3 pyramids sharing all three, and successive PO5X and TO2X2 polyhedra share corners to make sheets are held together through very long Te…O layers || (020) (Fig. 20). Although these compounds bonds (Fig. 19). The compounds [M5X2(TeO3)4] are not known as minerals, they are isostructural 2+ – with M = (Ni, Co or Mg), X = Cl and Br, (#92‒ with sophiite, [Zn2Cl2(SeO3)] (Semenova et al., 96) all have a structure with rather dense layers of 1992). [Co2Cl2(TeO3)] (#102), the Cl analogue of edge-sharing MO6 and MO5X octahedra || (200), #101, has a different, monoclinic structure with … braced by TeO3 groups. Long Te X bonds are layers of edge-sharing CoO4Cl2 and CoO3Cl3 important in holding the layers together (Fig. 19). octahedra || (001). In both cases, layers are again 2+ The compounds [PTX2(TeO3)] with P =(Co, braced by TeO3 groups and held together through 2+ – … Cu or Zn), T = Zn and X = Cl and also long Te X bonds (Fig. 20). [Cu3Br2(TeO3)2]

456 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

(#103) has CuO4 squares sharing all corners with In the compounds A2[(UO2)3O2(TeO3)2](A =K, edge-sharing pairs of CuO4Br pyramids to make Rb and Cs: #109‒111), edge-sharing pairs of UO7 loop-branched chains || y which feature a Cu polyhedra share both CN2 and CN3 oxygen atoms analogue of the ‘double triangle’ motif; these with UO6 octahedra to form ribbons || y, which in chains are bridged by TeO3 groups to make layers turn are bridged by TeO3 groups to form layers || || (001). Long Cu···Br bonds complete an elongated (101), which are held together by CN7‒8 interlayer + octahedron of ligands around square-coordinated A cations (Fig. 20). K4[(UO2)5O5(TeO3)2](#112) Cu1, and long Te…Br bonds hold the layers has a similar structure in which broader edge- together. sharing ribbons (4 × UO7 and 1 × UO6 polyhedra (NH4)2Mo3TeO 12 ≡ (NH4)2[Mo3O9(TeO3)] and per asymmetric unit) are bridged by TeO3 to form its Cs analogue (#104‒105) have a structure in layers which are also oriented || (101), with 8- 6+ + which Mo O6 octahedra share four corners to form coordinated K in the interlayer. Mo3O12 layers with the kagome net of 3- and 6- rings. Tellurium atoms share apical oxygen atoms 4+ of the Mo octahedra around each 3-ring, to make Structures with monomeric Te O3 as part of a 2– [Mo3O9(TeO3)] layers || (002). Layers are con- larger structural unit that is a framework … 2– nected through longer Te O bonds (2.92‒2.95 Å) The TeO3 pyramid is incorporated into an infinite which complete a very distorted octahedron around three-dimensional structural unit in compounds + + Te, as well as through interlayer NH4 or Cs ions #113‒194 (Table 12, deposited). The first two (Fig. 20). The positions of Mo and Te atoms examples are Ga2(TeO3)3-α, which in this context is correspond to those of O atoms in the tridymite more appropriately written [(Ga2.670.33)(TeO3)4], structure. Alternatively, the MoO6 and TeO3+3 and [(Ga2Zn)(TeO3)4](#113‒114), which both octahedra can be regarded as forming a hexagonal have the structure of eulytine, Bi4(SiO4)3 ≡ relative of the pyrochlore framework, in which half Si3(BiO3)4 (Menzer, 1931). This framework is of the Mo3 triangles link to Te above and below the made by CN2 oxygen atoms linking one CN4 (Ga, centre of the triangle. The structure is polar (space Zn) atom and one CN3 Te atom (Fig. 21). The group P63) as the TeO3 pyramids always point in cation sublattice (Ga,Zn)3Te 4 has the same arrange- the same sense along z.Rb2[W3O9(TeO3)] (#106) ment as the Th3P4 structure (Meisel, 1939; is almost isostructural, but with the symmetry O’Keeffe and Andersson, 1977; Hyde and reduced to P31c due to slight collapse of the layers. Andersson, 1989). The much less dense β poly- Ag6W3Te 4O16 ≡ Ag6[W2O6(TeO3)2][WO2(TeO3)2] morph of Ga2(TeO3)3 is described below (#136). 2+ (#107) has two types of infinite, strongly-bound The mineral choloalite, ideally Pb3[(Cu2.67 4– 5+ structural unit: a layer [W2Te 2O12] and a chain Sb0.33)(TeO3)6]Cl is almost isostructural with 2– [WTe2O8] ; for classification purposes, the layer SrCu(TeO3)2 =Sr3[Cu3(TeO3)6] (#115‒116). takes precedence. The chains are loop-branched, Again, the structure is cubic in symmetry, but with WO6 octahedra sharing four corners with TeO3 rather complex. CuO4 squares share all corners with groups to make W‒Te‒W‒Te 4-rings. They run || z Te, and TeO 3 groups share two corners with Cu, to and are stacked to make layers || (200), which form a framework with a large unit cell (a ≈ 12.5 Å) – alternate with the continuous W‒Te sheets. The and chiral symmetry (P4132). The Cl anion, if latter have WO6 and TeO3 polyhedra alternating in a present, is shared by three (Cu,Sb) atoms as a fifth 3-connected net of 4- and 8-rings with the ligand, while (Pb,Sr) is located in large interstices ‘apophyllite’ topology (cf. Fig. 11i). Layers are in irregular 9‒12 coordination (Sr) or 6‒9 (Pb) … held together through long Te O links and also (Fig. 21). Balyakinite, [Cu(TeO3)] (#117) has a + three types of interlayer Ag , in very irregular 5- structure in which edge-sharing pairs CuO5 square coordination (Fig. 20). pyramids link corners to form zigzag chains || x, Pb2[(UO2)(TeO3)3](#108) has a structure in which are cross-linked in the y and z directions into which UO7 pentagonal dipyramids share four a rather open framework by TeO3 groups (Fig. 21). equatorial oxygen atoms and two types of TeO3 Structures #142 and #297 are polymorphs. share two ligands to form layers || (020) of Although the unit-cell parameters and stoichiom- crumpled 8-rings in which Te and U cations etry of [Zn(TeO3)] (#118) are similar to those of alternate. A third type of TeO3 shares the remaining balyakinite, the structure is different. It features equatorial oxygen ligand of U, and projects into the edge-sharing pairs of ZnO5, but they link with four interlayer gap, where Pb2+ cations in irregular 7‒8 neighbouring dimers through corners to form coordination hold the structure together (Fig. 20). continuous corrugated layers || (002), with TeO3

457 A. G. CHRISTY ET AL. providing bridges between layers in the z direction. linked into a framework through TeO3 and SO4 Cu(SeO3) is not isostructural with balyakinite, but groups, which show some orientational disorder as one of its four polymorphs has the structure of Zn indicated by splitting of oxygen sites. (TeO3) (Effenberger, 1986; Hawthorne et al., [Ge(TeO3)2](#123) has a framework in which 1986), and another has the -type structure GeO6 octahedra and TeO3 pyramids share corners. of high-pressure Cu(TeO3)(#142) (Kohn et al., Interestingly, the GeTe2 substructure is a slight 1976). Teineite, Cu(TeO3)·2H2O ≡ [Cu monoclinic distortion of the rutile structure, with x (H2O)2(TeO3)] (#119), the dihydrate of balyakinite, as the pseudotetrad axis. The Ge‒O bonds of also features square pyramids, although these are argutite (rutile-type GeO2; cf. Haines et al., 2000) CuO3(H2O)2, and do not link to each other. The Cu are replaced by Ge‒O‒Te links in this compound. polyhedra share oxygens with Te so that Cu and Te HLi2[Ga3(TeO3)6]·6H2O(#124) has Ga‒O‒Te define an open 3-connected framework in which links between GaO6 octahedra and TeO3 pyramids, their locations correspond respectively to Ca and making a rhombohedral structure with alternating half of the Cl of the CaCl2 (orthorhombically layers of 2 × Ga surrounded by Te in an approxi- distorted rutile) structure (van Bever, 1935; Haines mate trigonal prism, and 1 × Ga surrounded et al., 2000). The structure is intrinsically enantio- octahedrally by Te. LiO3(H2O)3 octahedra share morphic (space group P212121) and has rather large faces with the former. There are three of each type channels || y, which are braced by hydrogen bonds of Ga layer per cell. Na3[Ga3(TeO3)6] · 7.2H2O between water molecules and TeO3 groups, and into (#125) has a closely related structure which retains which point the lone pairs of Te atoms (Fig. 21). the alternation of sparser and denser Ga layers, but Chalcomenite, Cu(SeO3)·2H2O, is isomorphic in which Ga is always surrounded by six Te in a (Pasero and Perchiazzi, 1989). Less obviously, the trigonal prismatic fashion, and there are only two of 5+ structural unit of LiV TeO 5 ≡ Li[(VO2)(TeO3)] each type of Ga layer per unit cell. Na3(H2O)5 (#120) is topologically the same as [Cu clusters with each Na bonded to four H2O and two (H2O)2(TeO3)] of teineite, although change in tellurite oxygen atoms also lie in the sparse Ga axial ratios and atomic coordinates close the layers, and another water site in the denser layers is channels (which would be || x if they existed). 36% occupied. K[Ga(TeO3)2] · 1.8H2O(#126) has Additional LiO5 polyhedra share two oxygen Ga of the sparse layers surrounded octahedrally by ligands with (Te + V), two with (Li + V) and one Te, as for #124. The layers are || (001), but the with a single V atom only. structure is triclinically distorted. K+ ions in 7‒8 2+ 6+ [(Cu6 Cl4)(Mo2 O8)(TeO3)2]·H2O(#121) has a coordination and H2O molecules occupy interstices framework made out of two chemically dissimilar in the sparse Ga layers (Fig. 21). components. Square-planar CuX4, CuO4 and Li6[Ga8.67(H2O)2(TeO3)14](#127) also has alter- Cu2O3Cl, link corners and some edges to form nating sparse and dense Ga layers, but these are thick layers || (001), which are braced by TeO3 quite different to those of #124‒126. The GaO6 groups and additional long Cu…Cl bonds. There are octahedra of the sparse layer have a pseudo-diad no tetrahedral molybate complexes: instead, MoO5 axis || z rather than a true triad axis, and those of the 4– square pyramids share edges to form [Mo2O8] denser layers occur in edge-sharing dimers Ga2O10, dimers in the interlayer region. These share the four which link into a honeycomb-like layer through non-apical oxygens with Cu of the layers on either CN3 water molecules. Out of three types of Te, Te2 side. Half-occupied H2O sites complete a very and Te3 link the two different types of Ga layer, distorted octahedron around Mo: these are at 2.50 Å along with CN5 Li+, while Te1 sit on triad axes and from the cation, compared to 1.70 Å for the apical connect Ga octahedra within the sparse layers. 3+ oxygen opposite (Fig. 21). [Cu7(TeO3)2(SO4) One dimorph of [Fe2 (TeO3)3](#128) has FeO6 (OH)6](#122) similarly has a framework in octahedra in an approximately face-centred ortho- which relatively dense layers are connected rhombic array of face-sharing Fe2O9 dimers, all through sparse bridges. There are five kinds of with Fe ≡ Fe vectors || y.TeO3 groups connect an Cu2+, all in square-planar coordination except that upper oxygen atom of one dimer, lower oxygen Cu5 has a fifth oxygen ligand if the threshold is set atom of a second dimer and middle oxygen atom of at 2.3 Å. Edge-sharing trimers Cu4 = Cu3 = Cu4 a third, to make a continuous framework. The other and Cu5 = Cu2 = Cu5 link corners to form complex dimorph (#129) has the same Pnma space group but chains || [101], with additional corners shared a topologically quite different structure in which between Cu4 and bridging Cu1, which further FeO6 octahedra share four corners to form Fe2O8 condense the chains into layers || (111). Layers are layers || (020). As the unshared ligands are cis to one

458 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

FIG. 22. Examples of structures with monomeric TeO3 pyramids that are part of larger structural units that are frameworks (Table 12, deposited). Small spheres: H (pale pink) and O (dark pink), when not part of a polyhedron. Large spheres: K (purple) and Na (dark yellow). Polyhedra: Co (magenta), Fe (orange-brown), Sb (brown-green), Te (dark green), V (blue) and Zn (pale grey).

another, the layers are highly corrugated. One of face-sharing octahedral dimers Zn2O9 which are two types of Te braces the Fe layer, with the lone cross-linked through TeO3 in a fashion very similar pair pointing into the interlayer gap, while the other to #128, except that the dimers are arranged in a type of Te bridges two Fe layers to make a very open hexagonal honeycomb pattern (Fig. 22). continuous framework, with its third ligand not Thus, the resulting framework has hexagonal bonded to Fe. [In2(TeO3)3](#130) is isostructural, channels || z that are very large (∼10 Å across). but was described in a different axial setting. cations occur in the channels in #131, Structures #131‒136 all have the microporous and are accompanied by water molecules framework, which has zeolitic ion- in NaH[Zn2(TeO3)3] · 2.67H2O(#132) and exchange properties. Na2[Zn2(TeO3)3](#131) has Na2[Zn2(TeO3)3] · 2.97H2O(#133).

459 A. G. CHRISTY ET AL. replaces Zn in #134. The negative charge on the Cl (#139) has a quite different type of structure, in framework can be modified by substituting triva- which linear chains || y of corner-sharing NbO6 lent cations for Zn2+, and other channel cations may octahedra pack in a trellis-like arrangement, and are + 2+ – substitute for Na . The channel cation is Mg in cross-linked through TeO3. Lone pairs and Cl 3+ the mineral zemannite itself, Mg0.45[(Fe1.12 anions are accommodated in large square channels || y. Zn0.80Mn0.08)(TeO3)3] · 4.08H2O(#135), which The [M(TeO3)] structures #140–142 (M = Co, Ni 2+ 3+ can be idealized as Mg0.5[(Zn Fe )(TeO3)3]· or Cu) are all of perovskite type. MO6 octahedra 4+ 4.5H2O, although the data of Miletich (1995a) share all corners to form a framework, while Te show that the mean charge on M can vary over the occupies the cubic cages thus defined. The range 2.33‒2.56. The channel contents are arranged octahedral tilt system is of a+b–b– type, as in 2+… … 2+ as chains [Mg(H2O)6] (H2O)3 [Mg(H2O)6] GdFeO3 (Glazer, 1972), producing a unit cell with … (H2O)3 that have local trigonal symmetry, but are space group Pnma and cell parameters √2× orientationally and translationally disordered. 2×√2 of the aristotypical perovskite . 2+ 3+ Kinichilite, ideally Mg0.5[(Mn Fe )(TeO3)3]· Bending of Fe‒O‒Fe links and displacement of 2+ 3+ 4.5H2O, and keystoneite, Mg0.5[(Ni Fe ) Gd in GdFeO3 reduce the Gd coordination from 12 (TeO3)3]·4.5H2O, have similar unit-cell parameters equidistant oxygen atoms to six at 2.26‒2.39 Å, two to zemannite, but have not had their structures at 2.82 Å and four effectively non-bonded oxygen refined (Miletich, 1995a). The new mineral ilir- atoms at >3.1 Å (Coppens and Eibschuetz, 1965). 3+ neyite, Mg0.5[(ZnMn )(TeO3)3]·4.5H2O, is also However, the displacement of Te in Co(TeO3)is isostructural (Pekov et al., 2015). The channels are much more extreme, giving three O at 1.90‒1.92 Å, completely empty and the framework electrostati- five at 2.70‒2.98 Å and four at >3.4 Å. Thus, Te cally neutral in [Ga2(TeO3)3]-β (#136), much less forms only three strong bonds, and acts as a brace dense than the α polymorph with the eulytine on the MO3 framework (Fig. 22). This form of Cu structure described above (#113). Synthetic (TeO3)(#142) is a high-pressure polymorph of 6+ analogues of zemannite, K2M2[SeO3]3 ·2H2O(M = #117 and #297. Note that Te in octahedral Co or Ni) are also known (Wildner, 1993). coordination can act as the smaller ‘B’ cation in 3+ , [Fe2 (H2O)(TeO3)3](#137) is tri- the perovskite structure: #562‒584 below, are clinic but has pseudotetragonal symmetry down the examples. An unusual example of Te4+ in the ‘B’ x direction. FeX6 octahedra occur in edge-sharing site of a defect perovskite is provided by #195, below. 3+ dimers Fe2O8(H2O)2, but these stack such that they [Fe F(TeO3)] (#143) has zigzag zweier chains can be derived from a continuous edge-sharing || y of edge-sharing FeO4F2 octahedra (the shared chain || x by deletion of every third Fe atom. The Fe edges are alternately F2 and O2). TeO3 groups link dimers of neighbouring chains are connected trios of neighbouring chains to make a framework. 5+ through TeO3 pyramids, which define the walls of In one polymorph of V2 Te 2O9 ≡ [V2O3(TeO3)2] nearly-square channels || x, which accommodate (#144), alternating VO5 and VO6 polyhedra (V1 the Te lone pairs (Fig. 22). There is a marked and V2 respectively) share corners to make a zigzag resemblance to the tetragonal structure of minium, vierer chain V2O9, with V2 at the angles in the 4+ 2+ Pb Pb2 O4 (Gavarri and Weigel, 1975) or scha- chain. The V1 polyhedron has a geometry that 2+ 3+ 4+ 5+ farzikite, Fe Sb2 O4 (Fischer and Pertlik, 1975). would be more typical for V than V :asquare The atomic arrangement of emmonsite can in fact pyramidwithfourV‒O distances 1.78‒2.00 Å, and be regarded as a threefold superstructure of the a very short distance of 1.58 Å corresponding to an 2+ 3+ schafarzikite type with ordered vacancies: Fe3 Sb6 apical V=O . The V2 geometry is an 3+ 4+ 2+ 6+ O12 =(Fe2 )(Te3 3)(O9(H2O)3). Co6 [Te O6] extremely distorted octahedron with four distances 4+ [Te O3]2Cl2 (#678, below) has a closely related 1.97‒2.30 Å to oxygen atoms that are shared with structure. [Ga2(H2O)3(TeO3)3](#138) has the V1, Te or both, and two much shorter cis distances Ga2Te 3 substructure arranged approximately like 1.60‒1.72 Å to unshared oxygen atoms. Thus, the the atoms of α-Ga2O3, which has the corundum structure appears to contain two types of vanadyl (V) structure (Marezio and Remeika, 1967). However, complex, [V=O]3+ and [O=V=O]+.TheVchainslie there are Te‒O‒Ga links from Te to only three out of in layers || (100). One of two types of Te shares two the four nearest Ga. There are two types of Ga atom, oxygen atoms with V1 + 2 × V2 of one chain and the one bonded to only tellurite oxygen atoms, while other oxygen atom with V2 of an adjacent chain. The the other centres a GaO3(H2O)3 octahedron. The other type of Te bridges between layers to complete structure is polar, as groups Ga1(TeO3)3Ga2(H2O)3 the framework. A second polymorph containing all point in the same sense along z. [Nb3O3(TeO3)4] Te 2O5 dimers is described below (#203).

460 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

3+ 3+ Sonoraite, Fe (TeO3)(OH)·H2O ≡ [Fe2 (OH)2 structure, two of which show orientational disorder, (H2O)(TeO3)2]·H2O(#145), has edge-sharing octa- evidenced by mutually exclusive split positions for hedral dimers Fe2O8(OH)2 and Fe2O4(OH)5(H2O) oxygen atoms. [Ni7(TeO3)6Cl2](#151) has NiO5Cl alternating and linked through shared OH– corners octahedra sharing edges in a very open honeycomb to make vierer chains || [101]. The chains are pattern, making very low-density layers || (003). packed in an approximately hexagonal array, and The framework is formed by TeO3 and additional TeO 3 groups link trios of neighbouring chains into a NiO6 between the layers and sharing edges with framework. The non-framework water molecule is them. Ni3(TeO3)2(OH)2 (#152) is more inform- loosely held in a structural cage between TeO3 atively written [Ni6(TeO3)4(OH)3](OH). It, and its groups. [Ta2O3(TeO3)2](#146) has a similar Co analogue (#153), have an unusual structure in stoichiometry for its structural unit, but a quite which face-sharing dimers of octahedral M2O7(OH)2 different structure in which TaO6 octahedra share share additional edges to form zigzag chains three corners to form a layer || (002) of 4- and 8- M4O10(OH)2 || z. These chains in turn share corners rings. The Te atoms are in the interlayer regions, to act as walls surrounding large channels (9 Å and half of the TeO3 groups share all three ligands diameter) along the 63 screw axis of the structure, and while the other half share only two, in order to link small channels along the triad axes (Fig. 22). The the Ta layers into a framework. The structure of overall composition of the resulting nanoporous 5+ stoichiometrically analogous [Sb2 O3(TeO3)2] framework is M12O24(OH)6 per unit cell. Two Te (#147) is again quite different. Half of the SbO6 occupy the small channels and another six brace the octahedra share four corners and half share two large channels, which contain two more very loosely 8– – corners to make [Sb2O9] ribbons of zigzagging 4- bound OH anions to complete the unit-cell content, rings || y. These ribbons pack in a herringbone M12(TeO3)8(OH)8. 6+ fashion, and are connected into a framework In [Ga2Mo O4(TeO3)2](#154), edge-sharing through four crystallographically distinct types of chains || y of GaO6 octahedra are linked through TeO 3 group (Fig. 22). The wide variety of structures chains [MoO4(TeO3)] of alternating TeO3 and possible for M2Te nX9 structural units is demon- distorted MoO6 octahedra (4 × 1.71‒1.99 and 2 × strated further by Na2[W2O6(TeO3)] (#148), which 2.37 Å) to form undulating layers || (002). A second has a structure in which eight types of WO6 type of Te connects these layers into a framework. octahedron share two to three corners to form K[Nb3O6(TeO3)2], its Ta analogue and the corre- corrugated layers || (200), which have bands of 4- sponding Rb compounds (#155‒158) have octahe- rings || y alternating with bands of 8-rings. Two of dral MO6 (M = Nb or Ta) sharing four corners to the four types of Te act as braces on particular W make corrugated layers of 4-rings, M3O12 || (020). layers, while the other two types link the layers into Interlayer TeO3 shares all three corners to link these a framework. Na+ cations lie between the layers, in layers into a framework. CN12 K+ ions are also in 4+ 5+ irregular 7‒8 coordination. K3[(V O)4(V O4) the interlayer gap. (TeO3)4]·4H2O(#149) has clusters of five VOn The structure of [Ni3(MoO4)(TeO3)2](#159) 4+ polyhedra: four very distorted octahedra V O6 bears some resemblance to those of #152‒153. (V‒O distances are 1 × 1.61, 4 × 1.96‒2.07 and 1 × Four zigzag chains of edge-sharing NiO6 and two 5+ 2.26 Å) and a V O4 distorted tetrahedron (2 × 1.63 of corner-sharing NiO5, all chains having the and 2 × 1.82 Å). The octahedra form two face- composition Ni2O8, share additional corners to sharing dimers V2O9, which each share one of form walls around large pseudohexagonal and their bridging oxygen atoms with the tetrahedron small pseudotrigonal channels || x, forming a to make a mixed-valence pentameric anion nanoporous framework Ni6O18. The small channels 4+ 5+ 19– [V4 V O20] . All oxygens which are not part are empty, but the large hexagonal channels are 2+ of the VO4 tetrahedron or the [V = O] cation are braced by four TeO3 pyramids and two MoO4 shared with TeO3 groups, which again connect trios tetrahedra. Reduction of some Ni coordination of neighbouring vanadate units into an open numbers to 5 occurs because of elimination of a framework which has large channels (7‒8Å bond to an oxygen atom of a neighbouring Ni diameter) running || y and z. Water molecules and polyhedron, preventing overbonding of the latter + CN 8‒10 K ions are in the channels (Fig. 22). oxygen, which is part of the MoO4 group. [Ni11(TeO3)10Cl2](#150) has five types of NiO6 [Co7(TeO3)4Br6](#160) has layers of cis- octahedra forming thick layers || (001), which are CoO4Br2 octahedra sharing edges to make layers linked into a framework through edge-sharing pairs with 7-rings, || (200). The layers are linked into a of NiO5Cl octahedra. Five types of TeO3 brace the framework via trans-CoO2Br4 octahedra, which

461 A. G. CHRISTY ET AL.

FIG. 23. Examples of structures with monomeric TeO3 pyramids that are part of larger structural frameworks (Table 12) and nabokoite, in which a TeO4 square pyramid is part of a structural layer (#172, Table 13, deposited). Small spheres: O (dark pink) when not part of a polyhedron. Large spheres: Cl (yellow-green), K (purple) and Na (dark yellow). Polyhedra: Cu (cyan), Fe (orange-brown), Mo (dark grey), S (yellow tetrahedra), Te (dark green) and U (yellow bipyramids).

share faces with octahedra in the layers above and rocksalt-like structure. These chains are linked below. Tellurium atoms brace the layers, rather than through two opposite ligands of additional FeO6 3+ acting as interlayer bridges. [Fe2 (TeO3)O2](#161) octahedra to make a very open nanoporous has corrugated layers of edge-sharing FeO6 octa- framework with rhombic channels || x of diameter hedra || (100), with Te bridging across the ∼12 × 8 Å (Fig. 23). TeO3 groups reinforce the interlayers. [Co2(H2O)(SO4)(TeO3)] and its Mn cross-links, and have their lone pairs pointing into analogue (#162‒163) have crankshaft chains || z of the large channels. While the non-tellurite O2– ion edge-sharing octahedra MO5(H2O) (M =Co or is part of the structural unit, in the core of the Fe chain, – Mn), which additionally link their H2O corners to Cl is only loosely bound, and sits in the channels. make undulating layers with 6-rings || (100). The K2[W3O9(TeO3)] (#166) has WO6 octahedra layers are braced by TeO3 but connected into a sharing four corners to form layers || (020) with framework by SO4 tetrahedra, which share two the 3- and 6-rings of the kagome net. Tellurium oxygen atoms with the layer on one side and one atoms link these layers into a framework, forming oxygen atom with the layer on the other. additional 3-rings with two Watoms on one or other [Zn2(MoO4)(TeO3)] (#164) has alternating ZnO6 side of the interlayer gap. in the and ZnO4 polyhedra sharing corners to make layers interlayer is 8-coordinated. [Ni6(Mo4O16)(TeO3)2] of 6-rings || (001). TeO3 groups span the 6-rings, (#167) has rhomb-shaped tetramolybdate anions 8– acting as braces, while interlayer MoO4 tetrahedra [Mo4O16] which are held together by two CN3 share two oxygen atoms with each adjacent Zn and four CN2 bridging oxygen atoms. Layers of 3+ layer to make a framework. [Fe3 O(TeO3)3]Cl molybdate anions || (200) alternate with layers (#165) has FeO6 octahedra sharing edges to make containing zigzag sechser chains of edge-sharing a helical vierer chain || x that is a thin fragment of a NiO6 running || y. The molybdate groups link Ni

462 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

FIG. 24. Examples of structures with monomeric TeO4 polyhedra that are part of larger structural units (Table 13, deposited). Large spheres: Ba (yellow-green) and Cd (pink). Polyhedra: Co (magenta), Mo (dark grey), Nb or Zn (pale grey), P (brown), S (yellow), Te (dark green) and V (blue). Only the heteropolyanion cluster is shown for #175.

chains of the same and successive layers to form a individual bond valences (0.22‒1.78 vu) but a framework. Between the molybdate groups, there narrow range of bond-valence sums of 5.82‒6.12 vu are channels || z containing the Te, which also cross- for all Mo, implying that there is no ordering of 5+ 6+ 5+ 6+ link the Ni layers. [(Mo2 Mo3 )O13(TeO3)] (#168) Mo and Mo . MoO6 polyhedra share four has five types of Mo in very distorted octahedral corners to form layers || (002). The layers are of a coordination. There is a very wide spread of Mo‒O modified ‘tungsten bronze’ type, in which bands of distances: all Mo atoms have one very short Mo‒O 4-rings || y alternate with bands of 3- and 6-rings. of 1.69‒1.71 Å, all except Mo1 have one very long Mo2‒Mo5, in the 4-rings, share additional corners (2.38‒2.46 Å), while the rest are 1.78‒2.13 Å. The with octahedral in the layers above and below, 5+ 6+ 4– bond-valence parameters of Brese and O’Keeffe connecting the layers into a [Mo2 Mo3 O16] (1991) give a correspondingly wide spread of anionic framework. The charge-balancing Te4+ ion

463 A. G. CHRISTY ET AL.

2+ + sits in the 6-ring of the layer (Fig. 23). The TeO3 fifthligandforoneoftheCu cations, and CN8 K 3+ group shares an edge with the Mo1 octahedron, (Fig. 23). Atlasovite, KCu6Fe BiO4(SO4)5Cl, is where 3- and 6-rings meet, and its remaining ligand closely associated and appears to be isostructural is one apical oxygen atom of the Mo1 octahedron of with nabokoite (Popova et al., 1987). the layer either above or below. A high-temperature Four-coordinate Te4+ is rare in the square- polymorph is described as #281 below. pyramidal geometry, but occurs much more often Ba2[Nb6O15(TeO3)2] and its Ta analogue (#169‒ in the ‘trigonal bipyramid – 1’ or ‘folded rhombus/ 170) have octahedral MO6 (M = Nb or Ta) sharing kite’ geometry of Fig. 4c. An example is the 2– corners to make a three-cation wide layer that is a pyrosulfate [Te(S2O7)2](#173). The (S2O7) 4+ slice of ReO3-type structure || (221) of the cubic anions are bidentate ligands for the Te cation, ReO3 cell. The layers are connected into a so neutral molecules are formed which consist of framework by sparse shared edges, which separate butterfly-like pairs of Te‒S‒S 3-rings. These are the interlayer into channels || y of the resulting held together through long Te…O bonds (Fig. 24). 2+ 6+ monoclinic cell. The channels contain CN11 Ba , In In2[Mo O3(TeO4)](TeO3), (#174), InO6 and while Te braces the layers but unusually has its lone InO8 polyhedra share corners and edges to form a pair directed in towards the centre of the layer rather stepped layer || (101), which is not treated as a than into the interlayer gap. Na4[(UO2)3(TeO3)5] structural unit here, given the high coordination (#171) has a large (a ≈ 17 Å) unit cell in a low- number of half of the In cations. The layers are symmetry cubic space group (I213). UO7 and TeO3 braced by isolated (TeO3) pyramids but also by polyhedra form a framework in which every MoO4 tetrahedra and TeO4 polyhedra, which share equatorial ligand of U links to one of three types a corner to form the dimeric anion [MoO3 3– … of Te. The Te2 and Te3 sites lie on triad axes, and (TeO4)] . Layers are held together by long Te O are arranged like 2 × 2 × 2 unit cubes of the CsCl bonds. A much more complex finite cluster occurs 4+ 5+ 6+ structure. Three Te1 and three U form a buckled in (NH4)9K[V4 V8 Mo12O65(TeO4)(TeO3)2]· hexagon around each Te2, and the equatorial 27H2O(#175). The clusters are very similar to the oxygen atoms of UO7 link to the central Te2, the expanded/modified Keggin/Dawson-type anions of nearest Te3, the two nearest Te1 of the same #54–62, but are included here because it includes hexagon and one Te1 of a neighbouring hexagon not only two TeO3 groups centring its two + (Fig. 23). Three types of Na are weakly held in dissimilar half-cages, but also a TeO4 polyhedron interstices, in irregular 3‒6 coordination. as part of one half-cage (Fig. 24). There is considerable (V, Mo) disorder in the half- cuboctahedral cages. One Keggin half-cuboctahedron 4+ Structures with neso Te X4–5 as part of the of composition [(V4.25Mo4.75)O30(TeO3)] shares structural unit edges and CN3 oxygens with the Mo octahedra of a Table 13 (deposited) shows structures #172‒194,in ring of three MoO6 octahedra alternating with three 5+ which TeX4 or TeX5 polyhedra do not link to other V O4 tetrahedra; the Mo and V polyhedra of this Te. However, it is interesting to note that unlike TeX3, ring also share corners with the other half- these polyhedra always link to some other relatively cuboctahedron [(V4.75Mo4.25)O30(TeO3)], which strongly bonded cation, and thus are always part of a has the CN4 Te sitting outside one of the square larger structural unit. Nabokoite, K[Cu7(TeO4) faces, and bonded to the oxygen atoms surrounding (SO4)5]Cl (#172) is the only example of a structure that face. The anions pack with their long axes 4–  with neso square-pyramidal [TeO4] anions (cf. approximately parallel to [102], and are held + + Fig. 4b). Favreauite, Pb[Cu6(BiO4)(SeO3)4(OH)] together through weak bonds to K and NH4 ions (H2O), is nearly isostructural according to Mills and H2O molecules. 5+ et al. (2014b), who noted that the lone-pair cations BaV2 TeO 8 ≡ Ba2[(VO2)4(TeO4)2](#176) has (Bi, Te) are partially surrounded by corner-sharing VO5 polyhedra forming edge-sharing dimers 6– 3– CuO4 squares to make a thick layer || (002), that can [V2O8] and isolated tetrahedra [VO4] .TeO4 be regarded as a slice of the structure of murdochite, polyhedra share an edge with VO5 and the 4+ Cu6Pb O8 (Dubler et al., 1983). The resemblance is remaining corners with two VO4 groups to form a emphasized if the arrangement is considered of zweier double chain with 8-rings, [(VO2)4 4– oxygen-centred tetrahedra OCu3A (A = Te and Pb), (TeO4)2] (Fig. 24). Expressing the V component + according to the approach of Krivovichev et al. as vanadyl [VO2] complexes is suggested by the (2013). The layers are braced by SO4 tetrahedra, bond distances: 2 × 1.65 and 2 × 1.78–1.83 Å for – while the interlayers contain Cl , which is a distant VO4 and 2 × 1.64–1.65 and 3 × 1.89–1.99 Å for

464 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

VO5. The chains run || y, and are flattened || (103); coordination number from 8 to 6, and the symmetry they are linked through CN10 Ba2+. The Sr analogue from tetragonal to orthorhombic, as seen for (#177) has a much more complex structure in which [M(MoO2)(TeO4)], (M = Mg, Mn, Co and Zn) eight kinds of VOn polyhedron occur as corner- (#182–185). Given the close structural relationship sharing dimers, either O3V‒O‒VO3 or O3V‒O‒VO4, and very strong layering, the Cd compound has and these are linked through TeO3 and TeO4 to make been grouped with these as having a layer rather sechser double chains with 6- and 10-rings, than chain structural unit, even though 8- 8– 2+ [V8O18(TeO4)2(TeO3)2] . The subchains are joined coordination would normally exclude Cd from 6+ through TeO4 and VO5 sharing an edge. Two the unit as too weakly bonded. In BaMo2 TeO 9 ≡ topologically similar but crystallographically distinct Ba[Mo O (TeO )] and its Wanalogue (#186–187),  2 5 4 types of such chain run || [110], and are connected MO6 octahedra (M = Mo or W) share three fac 2+ through CN8–10 Sr ions. (NH4)4[Mo6 corners to form undulating layers || (001) of 6-rings O16(TeO4)] · 2H2O and its Rb equivalent (#178– that are in chair configuration. The layers are 6– 179) have clusters [Mo6O22] in which the six Mo reinforced by TeO4 sharing edges with two Mo atoms are arranged as a pair of tetrahedra sharing an polyhedra and a corner with a third octahedron, while edge; they are held together through two CN4 oxygen the layers are held together by CN11 Ba2+ ions. 6+ atoms at the centres of the tetrahedra and eight CN2 The compounds A2Mo2 Te(PO4)2O6 ≡ A2[Mo2 oxygen atoms along edges. These clusters are linked P2O10(TeO4)] (A = Rb, Cs and Tl; #188–190) through Te into continuous complex chains || z,held alternating MoO6 octahedra and PO4 tetrahedra + + 6– together through NH4/Rb and water molecules. share corners to form layers [(MoO3)2(PO4)2] || The structural unit of Ba[NbO(PO3)(TeO4)] (002) with a 3-connected net of 4- and 8-rings. (#180) is a highly corrugated layer || (002). Interlayer TeO4 polyhedra link these layers into a Corner-sharing NbO6 octahedra form linear framework, sharing corners to make Te‒P‒Mo 3- chains || y. Each pair of adjacent Nb polyhedra rings. The A+ cations are in 9-coordination in the + then share additional corners with a TeO4 polyhe- interlayer. Note that Tl shows little sign of lone-pair dron and a PO4 tetrahedron to form a tetrahedral stereoactivity (Tl–O = 2.77–3.17 Å, compared to 2+ 4+ 2+ 4+ Nb2TeP cluster. The Te atom makes an additional 2.83–3.17 Å for Rb). Mn V2 TeO 7 ≡ [Mn V2 link to Nb in the next chain, thus joining chains into O3(TeO4)] (#191) has double chains || [110] in layers. Note that TeO4 and PO4 share one oxygen which pairs of VO5 alternate with pairs of VO6, atom: the formula above has been written to sharing edges and CN3 oxygen atoms in a manner emphasize the Te coordination, but the structural similar to the Te chain of Fig. 10a. These chains are 2– unit could equally be written [NbO(PO4)(TeO3)] . linked into double layers || (001) by markedly 2+ CN10 Ba share edges with the phosphate groups, asymmetric TeO3+1 groups (Te–O = 3 × 1.86–1.94 holding the layers together (Fig. 24). CdMo6+ and 1 × 2.34 Å; with no more until 2.87 Å), which TeO 6 ≡ [Cd(MoO2)(TeO4)] (#181) has a layered share edges with two VO6 of one chain and a corner structure that is a highly modified 1 × 1 × 2 with VO5 of an adjacent chain. The layers are then superstructure of the fluorite type with ordered linked into a framework through MnO6 octahedra, cations and also cation and anion vacancies, which also share edges with VO6 and TeO4.For (CdMoTe)(O62) ≡ Ca4F8. The cations occupy simplicity, the formula above does not indicate that ¾ of the sites in a ccp array, with a four-layer each V atom has one very close (1.64–1.67 Å), sequence along z in which layers repeat in the order approximately double-bonded oxygen ligand, as is Cd, (Mo+Te), □, (Mo+Te). Only long Te…O bonds typical for V4+. The remaining non-tellurite oxygen hold the structure together across the layers of atom is shared by one VO6 and two VO5 polyhedra. 5+ vacant cation sites. is 8-coordinated by In Zn3V2 TeO 10 ≡ [Zn3(VO3)2(TeO4)] (#192), oxygen atoms, but half of the oxygen sites that are two types of ZnO5 and one of ZnO6 polyhedra not adjacent to Cd are vacant. Displacements of the share edges and corners to make very thick, but remaining oxygen atoms reduce the coordination looped and low-density layers || (020). The higher- number of Te and Mo from 6 to 4, although the valence cations are linked into bow-shaped anions 6– geometries are different: respectively ‘trigonal [O3V‒O‒TeO 2‒O‒VO3] , which are embedded in bipyramid – 1’ and tetrahedral. The TeO4 and the Zn layers, but also cross-link them into a MoO4 polyhedra share corners to form chains framework through one of the terminal vanadate 2–  2+ [MoTeO6] that run || [110] and [110] in alternate groups (Fig. 24). Co6 Te 5O16 ≡ [Co6(TeO4) layers along z (Fig. 24). When smaller divalent (TeO3)4](#193) has blocks of edge-sharing tetra- cations replace Cd, a small lattice strain reduces the mers of CoO6 octahedra sharing corners with

465 A. G. CHRISTY ET AL. edge-sharing dimers of CoO5 to make a framework chains into layers || (010) in such a way that Te < (V = with large channels running || y. Four types of TeOn V) > Te ‘double triangle’ clusters are formed. As is groups cross-link across the channels and other typical for V4+, the distance to the non-tellurite interstices between the Co blocks. The only oxygen ligand is very short (1.595 Å). The layers 2+ … … example of TeX5 in a framework is Co3 Te 2 are held together via long Te O and Te F links. 2+ 3+ (PO4)2O2(OH)4 ≡ [Co3(PO2)2(TeO3(OH)2)2](#194), Fe8Cu3Te 12O32Cl10 ≡ [(Fe Fe7 )(Te2O5)4(TeO3)4] 1+ 1+ which has trans edge-sharing chains of CoO6 (Cu2 Cl6)(Cu Cl2)Cl2 (#200) has zigzag chains of octahedra running || y. These are linked into layers || edge-sharing FeO6 polyhedra || z, which share (200) through corner-sharing chains of alternating corners to make layers || (200). These layers are PO4 tetrahedra and TeO3(OH)2 square pyramids, braced by the monomeric and dimeric Te anions. 3– – [TePO5(OH)2] , and then into a framework Between the layers lie three types of Cl anions. through interlayer CoO2(OH)4 polyhedra. One of these makes long bonds to the Te of Te2O5 in the adjacent layers, while the other Cl– anions form chains of edge-sharing tetrahedra || z. The tetra- 4+ 1+ Dimeric Te oxyanions [Te2Xn](n=5–9) hedral interstices are half occupied by Cu , which Compounds with dimeric sorotellurite groups are also occupies linear twofold coordinated sites in the #195–227, shown in Table 14 (deposited). The tetrahedron edges that are || y. Thus, a chain is 2– 4– – simplest example of the [Te2O5] anion (Fig. 8a)is formed of alternating [Cu2Cl6] and [CuCl2] provided by Cs2[Te2O5](#195). Interestingly, the anions (Fig. 25). structure can be regarded as a defect perovskite, The elegant framework structure of [Cu2(Te2O5) 1 with /6 of the anions missing. The orthorhombic Cl2] and its Br analogue (#201–202) has square unit cell corresponds to a 2√2×2√2 × 2 supercell pyramids CuO4X (X = Cl or Br) that share edges in + of the aristotypical perovskite cube, with Cs in the groups of four to make clusters with a Cu4O4 cube large-cation A positions and Te in B sites. The at the core and have4 ¯ point symmetry. These Te 2O5 dimers are separated from one another by clusters sit in columns || z, and are linked to their vacancies on the anion sites and asymmetrical neighbours by corner-sharing with Te2O5 groups, Te–O…Te links, where the short distances are 1.83– which act as the walls of ∼6 Å diameter square 1.97 Å and the long ones are 2.68–4.43 Å. The Te– channels || z. The channels accommodate the X– Te vectors of anions point along [110] or [110] in a anions and Te lone pairs (Fig. 25). Our second + 5+ herringbone pattern (Fig. 25). The Cs ions are in 9- polymorph of V2 Te 2O9 ≡ [(VO2)2(Te2O5)] (#203) coordination. Ba [Te O ](TeO )Br (#196) has has corner-sharing zweier chains of VO polyhedra 3 2 5 3 2 5  edge-sharing BaO8Br and BaO5Br3 polyhedra that lie in layers || (400) and run || [011] or [011] in forming columns || y, which share edges sparsely alternate layers. Te2O5 groups bridge two V chains to surround elongated micelles. These channels of one layer and two chains of the next to make a accommodate the Br– anions and also the lone pairs framework. A polymorph with monomeric rather of the Te dimers and monomers, which brace the than dimeric TeO3 groups was described above 3+ micelle walls. In Nd2[Te2O5](TeO3)(MoO4)(#197), (#144). Cr2 Te 4O11 ≡ [Cr2(Te2O5)(TeO3)2](#204) NdO8 polyhedra share edges to form undulating has edge-sharing dimers of CrO6 octahedra linked honeycomb layers || (200). The layers are braced by into a framework through Te; only the central molybdate and tellurite groups, and are held oxygen of Te2O5 does not link to Cr. … together only by long Te O bonds. Ni3.4[Ni30(Te2O5)6(TeO3)20]Br14.8 (#205) and TiTeO F ≡ [Ti OF (Te O )] (#198) has TiO Ni [Ni (Te O ) (TeO ) ]Cl (#206) are iso- 3 2 2 4 2 5 2 4.5 30 2 5 6 3 20 18.45  (O0.5F0.5)2F2 octahedra sharing corners to make typical compounds with large cubic unit cells (Im3, 8– zweier double chains of 4-rings, [Ti4O8F8] a ≈ 17.5 Å). The ordered part of the structure running || x.Te2O5 groups share four oxygen consists of NiO6 and NiO5 polyhedra which shared atoms with a square of adjacent Ti atoms in the edges to form large icosahedral cages, braced by the 2+ 8+ double chain to make Te2Ti4 triangular prisms. Te anions, [Ni30(Te2O5)6(TeO3)20] . The rest of Long (2.73–2.77 Å) Te…O bonds link the resulting the structure shows substantial disorder. The large loop-branched double chains into double layers cages contain an icosahedral cluster of 12 Ni || (020), which are then held together through positions which cannot be >50% occupied due to … 4+ … 2.56 Å Te F bonds (Fig. 25). V2 Te 2O7F2 ≡ short Ni Ni distances. Partly occupied halide [(VO)2F2(Te2O5)] (#199) has cis-VO4F2 octahedra anion sites are at the core of these clusters, sharing alternately O2 and F2 edges to make zigzag surrounding their exteriors so that the additional 2+ – zweier chains || x.Te2O5 groups cross-link the V Ni are in approximate 4-coordination by (Br,Cl) ,

466 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

4+ FIG. 25. Examples of structures with Te2 O5–6 dimers (Table 14, deposited). Small spheres: Cl (yellow-green), N (brown) and O (dark pink) when not part of a polyhedron. Large spheres: Cs (blue). Polyhedra: Cu (cyan), Fe (orange- brown), S (yellow), Te (dark green), Ti (pale grey) and W (dark grey).

4– and halfway between the Ni clusters in channels structural unit, [Te2O6] (Fig. 8b). The shortest || < 100>, making long Te…(Br,Cl) bonds. Te‒O distance is 2.18 Å; there are no others until – Ho11[Te2O6]2(TeO3)12Cl (#207) has layers || 2.47 Å. The Cl ion is loosely bound in the centre of (012) of edge-sharing HoO6–8 polyhedra, sparsely the channels, into which the Te lone pairs also connected into a framework with channels running point. Moctezumite, Pb[(UO2)(Te2O6)] (#208) has || x. The walls of the channels are braced by six similar Te2O6 dimers, fringing zigzag chains of types of monomeric (TeO )2– and also a dimer in edge-sharing UO polyhedra to form broad ribbons 3 7  which TeO3 shares a corner with TeO4 to form the || y. The ribbons lie in layers || (102), which are held

467 A. G. CHRISTY ET AL.

4+ FIG. 26. Examples of structures with soro groups Te2 O6–8 or Te3O8 (Tables 14–15, deposited). Large spheres: Ca (orange), Dy (light yellow), Na (dark yellow) and Tl (grey). Black triangles in mroseite, #216:CO3 groups. Polyhedra: As (brown-green), Mo (grey), Te (dark green), U (yellow) and V (blue).

+ 5+ together by PbO3+4 polyhedra. A high-pressure NH4 ions (Fig. 25). InV Te 2O8 ≡ [In(VO2) (5.09 GPa) structure of (NH4)2WTe2O8 ≡ (Te2O6)] (#210) has zigzag corner-sharing chains (NH4)2[WO2(Te2O6)] (#209) has layers || (100) in of InO6 octahedra || y, sharing additional corners which WO6 octahedra share four corners and each with VO4 tetrahedra to make In‒In‒In‒V 4-rings. Te of Te 2O6 shares two, to form a net of Te‒W‒Te‒ Te 2O6 groups link the resulting ribbons to their Te‒W 5-rings which has the topology of the ‘Cairo neighbours to form thick layers || (101), held tiling’ (Hyde and Andersson, 1989), seen in less together only through long Te…O bonds. Showing crumpled form in the tetrahedral sheet of the the V as vanadyl is validated by the asymmetry in melilite group of minerals, e.g. (Ca,Na)2[(Al,Si, V‒O distances (2 × 1.61‒1.69 Å and 2 × 1.81‒1.83 Å). 3+ Mg)3O7] (Smith, 1953). Layers are held together by Poughite, Fe2 Te 2O6(SO4)·3H2O ≡ [Fe2(H2O)2

468 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

(SO4)(Te2O6)] · H2O(#211), has an edge-sharing little lone-pair stereoactivity (8 × O at 2.63–3.13 Å) dimer of FeO5(H2O) octahedra sharing additional and Tl2 with much less symmetrical coordination corners with an SO4 tetrahedron to form a finite (3 × O at 2.49–2.69 Å and four more at 3.27–3.56 Å) 8– 4+ 3-ring cluster [Fe2O6(H2O)2(SO4)] . These are (Fig. 26). The β phase of V TeO 4 ≡ linked together in groups of four through Te2O6 to [(VO)2(Te2O6)], stable at high-temperature, has make layers || (020), with the remaining H2O corner-sharing VO5 making zigzag chains || (#222); molecule in the interlayer (Fig. 25). Sr[Cu2Cl the V polyhedra share edges with Te2O6 to make (Te2O6)]Cl and the isostructural Ba compound layers || (100) (Fig. 26). The vanadyl oxygen atom (#212‒213)haveTe2O6 sharing all six oxygen is at 1.61 Å from V, but also makes three weak atoms with Cu2O6Cl dimers of CuO4 and CuO3Cl bonds to Te of the next layer (2.96–3.25 Å). There is squares, to make a rather open framework, with little resemblance to the raspite structure of the α – 5+ channels || x and y which contain the remaining Cl dimorph (#82). NiV2 Te 2O10 ≡ [Ni(VO2)2(Te2O6)] 2+ and also (Sr,Ba) ions, coordinated by 6O + 2Cl. (#223) has distorted VO6 octahedra sharing edges 6– Pb3Te 2O6Cl2 ≡ Pb6[Te2O6](TeO3)2Cl2 and its Br to make zigzag chains [V2O8] || x.Te2O6 groups analogue (#214‒215) contain edge-sharing dimers each bridge four such chains, while NiO6 octahedra of TeO (Fig. 8c). They have edge-sharing layers || bridge two V chains and two Te O groups,  4 2 6 (201) of PbO4X4, PbO5X3 and PbO8X polyhedra forming a quite dense framework with many (X = Cl or Br). The layers are braced by Te2O6 and Ni‒V‒V and Ni‒V‒Te 3-rings. TeO 3 groups, and loosely held into a framework BaMo2Te 2O11 ·H2O ≡ Ba[Mo2O4(Te2O7)] · H2O … through Pb‒X and Te X bonds. The Te‒O bonds (#224) has cis-corner-sharing MoO6 octahedra out to 2.05 Å in mroseite (#216) define a neutral forming helical vierer chains || y. These are linked 0 dimer [Te2O4] , made from an edge-sharing pair of into thick layers || (002) via Te dimers which are 6– TeO 3 pyramids, suggesting that the formula be corner-sharing [Te2O7] groups (Fig. 8d), if Te–O written Ca2(Te2O4)[CO3]2. However, each Te is distances out to 2.43 Å are included. Water only 2.31 Å from a carbonate oxygen atom, so it molecules and CN10 Ba2+ ions are between the 5+ could also be expressed as Ca[(CO2)2(Te2O6)]. The layers. Polymorph I of TeO(As O3OH) ≡ 4– S-shaped [(CO2)2(Te2O6)] heteropolyanions pack [(AsOH)2(Te2O8)] (#225), like many compounds in a herringbone pattern to form strongly corrugated of Te with other high bond-valence cations, has 4+ layers || (002), which are held together through CN8 Te in 5-coordination. Here, two TeO5 pyramids 2+ 5+ 8– Ca ions (Fig. 26). NaV TeO 5 ≡ Na2[(VO2)2 share edges to make a [Te2O8] dimer (Fig. 8e). + + 2– (Te2O6)] is isotypical with its K and Ag analogues These share corners with [AsO3OH] tetrahedra to (#217‒219). In these compounds, edge-sharing make As<(Te=Te)>As clusters which are yet Te 2O6 dimers share corners with VO4 tetrahedra to another variant of the common ‘double triangle’ make chains with 4-rings Te‒V‒Te‒V,which extend motif (Fig. 26). The remaining unprotonated || [101]. These pack, herringbone fashion, in layers || oxygen atom on As is shared with Te of a (020). Large cations between the layers are in 8-fold neighbouring cluster, linking clusters to form coordination, but while this is fairly regular for K+ double chains || y. Chains are held together (K‒O = 2.67‒2.99 Å), it is less so for the smaller through hydrogen bonds and long Te…O bonds. cations (Na‒OandAg‒O both = 2.41‒2.91 Å). Tellurium polyhedra are condensed further in 5+ Ba2V2 Te 2O11 ≡ Ba2[(VO2)(VO3)(Te2O6)] (#220) polymorph II (#299, below). The edge-sharing has Te2O6 groups alternating with VO4 tetrahedra Te 2O8 group also features in Ba2TeO(PO4)2 ≡ to make a dreier chain || y, which has a second type Ba4[(PO2)2(PO3)2(Te2O8)] (#226), where such of VO4 as an open branch on one of the central groups are bridged by pairs of corner-sharing PO4 oxygen atoms of each Te2O6. The chains lie in tetrahedra to form dreier chains with [‒Te = Te‒P‒] layers || (200), which have BaO8–10 polyhedra backbones, not unlike the Te‒V chains of #220. between them. The α form of Tl2(UO2)Te2O6 ≡ Again, a second type of tetrahedron forms open Tl4[(UO2)2(Te2O6)(TeO3)2](#221) has a β dimorph branches, but this time, the additional PO4 groups with monomeric TeO3 in a heteropoly chain attach to a single Te atom rather than to a bridging structure, #70 above. The α structure has edge- oxygen of the chain backbone. The resulting  sharing pairs of UO7 polyhedra sharing further ribbons lie in layers || (101), with BaO9–11 edges with Te2O6 to make ribbons || [110]. The U between them. Te2O(PO4)2 ≡ [P2(Te2O9)] (#227) 4+ polyhedra are bridged by additional TeO3 to link the again has CN5 Te (cf. # 225), but this time in  10– ribbons into layers || (111) with 12-rings and U‒Te‒ corner-sharing dimers [Te2O9] (Fig. 8f ). The U‒Te 4-rings. Between the layers are Tl1 showing dimers are linked into a framework through

469 A. G. CHRISTY ET AL.

4+ FIG. 27. Examples of structures with soro groups Te3 O8–11 or Te4O11 (Table 15, deposited). Large spheres: rare-earth elements Dy or La (light yellow) and Na (dark yellow). Polyhedra: As (brown-green), Nb (grey) and Te (dark green).

two types of PO4 tetrahedra: one type shares run || x and are linked into a framework through a oxygen atoms with Te atoms of four different few additional shared edges. Two types of 4– dimers, whereas the other type links only three [Te3O8] (Fig. 8g) and two types of monomeric 2– dimers, but forms a Te‒Te‒P 3-ring with both Te [TeO3] line channels || x in the Sr–O matrix. atoms of one of them. Ba3[Te3O8](TeO3)(#229) is nearly isostructural, although with x and z axes exchanged, as 4+ Trimeric Te oxyanions [Te3Xn](n=8–11) published. However, it retains a centre of inversion Trimeric sorotellurite groups occur in structures symmetry that is lost in the Sr compound, #228–249 (Table 15, deposited). Sr3[Te3O8](TeO3) concomitant with which all Te3O8 groups are (#228) has a triclinic structure in which 2-wide and equivalent and Ba2+ has CN = 8–9. Both structures 4-wide ribbons of edge-sharing SrO7–9 polyhedra resemble the unexpectedly complex structures of

470 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS the (Ca,Sr)(TeO3) phases (#9‒15). BaLa2[Te3O8] NaNb3Te 4O16 ≡ Na[Nb3O5(Te3O8)(TeO3)] (#246) (TeO3)2 (#230) is quite different, in that it has layers has broader zweier triple chains of 4-rings || y of || (200) of edge-sharing BaO12 and LaO8 polyhedra, NbO6 octahedra, which are decorated by the TeO3 which are braced by TeO3 groups and bridged by monomer, making Nb‒Nb‒Te 3-rings. The Te3O8 Te 3O8. The series A2[Te3O8](Te2O5)(A = Dy, Ho, groups link each Nb ribbon to three of its Er, Tm, Yb, Lu and Y; #231–237) show even less neighbours in a framework. The CN8 Na+ ion lies polymerization of large-cation polyhedra. They between the TeO3 monomers of neighbouring Nb have 4-wide ribbons of edge-sharing AO7–8 poly- chains. Na1.4Nb3Te 4.9O18 ≡ Na1.4[Nb3O4(Te2.9O8) hedra running || x. Interestingly, the Te3O8 groups (TeO3)2](#247) has a very similar composition and do not link the ribbons, but only decorate their two very similar unit-cell parameters, but the edges, while Te2O5 groups link the ribbons into topology is quite different. The NbO6 octahedra thick double layers || (001) (Fig. 26). Long bonds to form single and double zweier chains || y, that both types of tellurite anion hold the layers together. alternate in the x direction. Te3O8 groups are Sr4[Te3O8]Cl4 (#238) has SrO8Cl, SrO4Cl5 and slightly defective, in that the central Te is only 90% SrO2Cl7 polyhedra. These share O2 edges to form occupied. They link Nb single chains with each 8-cation-wide ribbons of a fluorite-like structure || y, other and with neighbouring double chains, which connect through the longer Sr–Cl bonds into forming an open framework with numerous Nb‒ continuous layers || (201), and more sparsely into a Nb‒Te and Nb‒Te‒Te 3-rings, while two types of three-dimensional framework. The Te3O8 groups TeO 3 monomer form additional Nb‒Nb‒Te rings + brace the Sr–O ribbons. In La2[Te3O8](MoO4) on the double chains. The CN8 Na ions partially (#239), LaO9 polyhedra share faces, edges and occupy sites that lie in channels || y (Fig. 27). corners to form an open framework La2O11 that has Dy2(TeO3)3 ≡ Dy4[Te3O9](TeO3)(#248) has a channels || x and y.Te3O8 groups run down the surprisingly complex structure with thick, loop- length of the y channels, sharing all oxygen atoms branched layers of edge-sharing DyO7–8 polyhedra with La, while MoO4 tetrahedra brace the x || (100). These are bridged by V-shaped corner- 6– channels, sharing only three ligands with La. sharing trimers [Te3O9] , including Te–O dis- Na2Mo3Te 3O16 ≡ Na2[Mo3O8(Te3O8)] and its tances out to 2.44 Å (Fig. 8h), and three types of 2– 5+ Ag analogue (#240–241) have MoO6 octahedra independent (TeO3) ion (Fig. 27). The high As – sharing edges to form V-shaped trimers [Mo2 = O bond valence (∼1.25 vu) leads to Te adopting Mo1=Mo2], which are linked via Te3O8 groups 5-coordination in Te3O3(AsO4)2 ≡ [As2(Te3O11)] [Te2‒Te1‒Te2] to form complex loop-branched (#249). Three TeO5 pyramids share a common dreier chains || x. The chain has two equivalent CN3 oxygen atom and two CN2 oxygen atoms to 10– backbones ‒Te1‒Te2‒Mo2‒ and ‒Te1‒Mo2‒Te2‒, form [Te3O11] trimers (Fig. 8i). AsO4 tetrahedra which intersect at Te1 and are further braced share two corners with one such trimer and one through Mo1=Mo2 and a CN3 oxygen atom each with two neighbouring trimers to form which bonds to Mo1, Mo2 and Te2. Chains are continuous layers || (010), with Te‒Te‒As 3-rings, held together via CN6–8 (Na, Ag)+ (Fig. 26). Te‒As‒Te‒As 4-rings and Te‒Te‒As‒Te‒Te‒As 6- Ca[Co2Cl2(Te3O8)] and its isostructural Sr‒Co and rings. Layers are held together only through long Sr‒Ni analogues (#242–244) have a structure in Te …O bonds (Fig. 27). which MO5Cl octahedra (M = Co or Ni) share edges to form helical vierer chains || y (cf. #165 and 224). 4+ Te 3O8 groups bridge these chains to form double Finite Te oxyanions [TemXn] with m  4 layers || (002), the long axes of the Te anions Na2Te 2O5 ·2H2O ≡ Na4[Te4O10]·4H2O(#250)  4– pointing || [110] on one side of the layer and || [110] has linear [Te4O10] tetramers with a central on the other side. CN8 (Ca,Sr)2+ ions sit in the cores shared edge (Fig. 8j). These lie in layers || (001) of the double layers, which are held together with their long axes all || [110]. Water molecules … + through long Te Cl interactions. Nb2Te 3O11 ≡ and CN5–6Na ions lie between the layers. The + [Nb2O3(Te3O8)] (#245) has ladder-like einer analogous NH4 compound (#251) has Te4O10 double chains of 4-rings || z of corner-sharing groups lining up nose-to-tail to form rods || [101], + NbO6 octahedra, arranged in a herringbone pattern. which pack in a hexagonal array, with NH4 ions and Te 3O8 groups share two corners with octahedra in H2O molecules between them. Sc2Te 5O13 ≡ each of the Nb chains in the ±x directions and one Sc4[Te4O10](Te3O8)2 (#252) has ScO6 and ScO7 corner with each of the Nb chains in the ±y polyhedra sharing alternately corners and edges to directions, forming a framework (Fig. 27). form zigzag chains || x. Linear Te4O11 groups

471 A. G. CHRISTY ET AL.

4+ FIG. 28. Examples of structures with soro groups Te4 O11,Te5O12,Te10O26 or cyclo Te6O12 (Table 15, deposited). Small spheres: N (brown) and O (dark pink) when not part of a polyhedron. Medium spheres: Br (red). Large spheres: Ba (yellow-green). Polyhedra: Cu (cyan), Mo (dark grey), Nb (pale grey) and Te (dark green).

pointing || [011] connect the Sc chains to make which are weakly bonded to Te. Unusually, double layers || (001), while C-shaped Te3O8 the CuO6 octahedron is not much less regular groups wrap around individual Sc chains. The than MnO6 (Cu–O = 1.99–2.32 Å, vs. Mn–O= double layers contain slot-like micelles || x which 2.12–2.28 Å). accommodate most of the Te lone pairs; layers are The compounds A2[Te4O11](A =La–Nd, Sm–Lu … held together through long Te O bonds. Ca2[Cu and Y; #256–270) show the progressive, monotonic (Te4O10)]Cl2 (#253) has Te4O10 groups pointing || change in parameters and properties with atomic [011], sharing corners with CuO4 squares to make a number that is characteristic of the lanthanide continuous layer || (011). The Ca2+ ions form elements. In particular, the fourth-shortest Te2–O zigzag edge-sharing chains of CaO7 polyhedra || x distance changes so much along the series, from between the Cu‒Te layers. Cl– ions also lie in the 2.515 Å for the La compound to 2.354 Å for Lu, interlayer gap, and complete a very elongated that the classification of the Te anion(s) changes if octahedron around Cu2+ (Cu–Cl = 2.74 Å). the usual ‘strong bond’ threshold of 2.40–2.45 Å is 2+ Sm2Mn Te 5O13Cl2 ≡ Sm4[Mn2(Te4O10)(Te3O8)2] used. For such a threshold, the compounds of larger Cl and isostructural Dy [Cu (Te O )(Te O ) ] A cations such as La would be regarded as having 4 4 2 4 10 3 8 2 Br4 (#254–255) have Te anions pointing || [102] dimeric [Te2O5] + two monomeric TeO3 groups. In and arranged in layers || (201); each layer contains order to keep this family of isostructural com- both Te4O10 and Te3O8 groups. The anions are held pounds together, a threshold of 2.53 Å is used for all together by (Mn,Cu)O6 octahedra between the of them, and they all classify as having corner- 6– layers, which are considered part of the structural linked tetramers [Te4O11] (Fig. 8k), with the long unit, and edge-sharing ribbons of (Sm,Dy)O8 Te–O bonds linking the terminal Te1 atoms to the polyhedra, which are not. A very open core Te2–Te2 dimer. The third-shortest Te2–O framework results, in which there remain elongated distance increases slightly from 1.989 to 2.022 Å channels || y which accommodate (Cl,Br)– anions, as the A cation decreases in size from La to Lu. The

472 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS structure is relatively simple, with layers || (002) of Cl– anions are held loosely, in the centres of large edge-sharing AO polyhedra linked through linear and small channels. Nb Te O ≡ [Nb O 8  2 4 13 8 8 Te 4O11 groups that all point || [201] (Fig. 27). (Te10O26)(TeO3)6](#279) has zweier chains of Ba2[Cu2(Te4O11)]Br2 (#271) has layers in which corner-sharing NbO6 octahedra || x. The pseudo- Te 4O11 groups with long axes || y share corners with monoclinic unit cell contains four distinct such CuO4 squares to make sheets with Cu‒Te‒Te 3- chains, but despite the apparent simplicity of this rings, Cu‒Te‒Cu‒Te 4-rings and Cu‒Te‒Te‒Cu‒ arrangement, these are connected together through Te‒Te 6-rings. The sheets are parallel to (001) but a remarkably complex arrangement of Te atoms. haveapolarityinthez direction; a pair of such sheets There are eight distinct Te sites. Sites Te2, Te3 and occurs back-to-back in every c repeat. BaO10 Te5 are in monomeric TeO3 groups that share polyhedra occur in the interlayer gaps that that are corners with Nb to make 4-cation-wide ribbons || x faced by Cu, while Br– anions occur in the gap that is with Nb‒Nb‒Te 3-rings (alternately on each side of lined by Te atoms (Fig. 28). A very similar Cu–Te the Nb‒O backbones, similar to the chain of 2+ 1+ sheet occurs in Ba4[Cu2 (Te4O11)]2(Cu4 Cl8) Fig. 15c), Nb‒Te‒Nb‒Te 4-rings and Nb‒Nb‒Te‒ (#272). The sheets again occur in back-to-back Nb‒Nb‒Nb‒Te 7-rings (Fig. 28). The ribbons lie in pairs, but this time they are parallel to (010), with layers || (011), which are then bridged by the open-  2+ 12– Te 4O11 groups trending || [101]. Again, the Cu ions branched decameric anion [Te10O26] of Fig. 8o, face an interlayer unit of BaO10 polyhedra. However, in which a central edge-sharing pair of Te8 are the Te side of the sheets faces a wide interlayer space linked through Te6 to Te1, which is then connected 1+ 4– that contains [Cu4 Cl8] clusters. These consist of a to both Te4 and Te7. The long axis of the anion … … central pair of edge-sharing CuCl4 tetrahedra, linked Te7 Te8 = Te8 Te7 is approximately || [311] in through corners to two CuOCl2 triangles. The long the interlayer gap, while the Te4 branches complete axis of the cluster is || [101], approximately the Nb‒Te layers || (011). Note that this description perpendicular to that of the Te4O11 groups. The is valid if the strong bonding threshold for Te is terminal Cu1+ atoms share the middle oxygen atoms chosen in the range 2.36–2.44 Å; however, two of the Te‒O anions, thus providing additional slightly longer Te–O bonds (2.44–2.47 Å) connect bridges between them, but are not counted as part the finite decamers into infinite open-branched of the structural unit due to the low valence of Cu. achter chains, in which the additional bridging 2+ [Co5 (Te4O11)Cl4](#273) has thick layers || (100) of oxygens are CN3, shared by Te7 of two different corner- and edge-sharing CoO4Cl pyramids, decamers and Te2 as a new branch. (NH4)6Mo8 CoO5Cl trigonal prisms and octahedra, and cis- Te 8O43 ·H2O ≡ (NH4)6[(MoO3)6(Te6O12)(TeO3)2] 4+ CoO4Cl2 octahedra. The layers are braced by Te4O11 (Mo2O7)·H2O(#280) has the only true cyclo Te groups with their long axes || [011], and are held complex of the present study. Hexagonal rings … … 0 2– together though long Te O and Te Cl bonds. [Te6O12] (Fig. 8n) and monomeric [TeO3] anions [Cu4(Te5O12)Cl4](#274) has an elegant tetrag- are linked into a layer || (001) through edge-sharing onal structure in which the tellurite anion is the dimers of MoO6 octahedra. Additional corner- 2– pinwheel-like Te5O12 pentamer of Fig. 8l. CuO4Cl sharing dimers of MoO4 tetrahedra [Mo2O7] , square pyramids occur in clusters of four, where the with point symmetry 3, lie in the centres of the + oxygen atoms of the cube-shaped Cu4O4 cluster hexagonal rings. The NH4 cations and water core are tetrahedrally coordinated by 3 Cu + 1 Te, molecules lie in the interlayer gap (Fig. 28). thus linking Te and Cu polyhedra into an open framework. The Cl– anions are in channels || z, and make additional long bonds to Cu and Te (Fig. 28). 4+ ≡ Structures with Te complexes that are infinite Nd5MoTe7O23Cl3 Nd5(MoO4)[Te5O13](TeO3)2Cl3, chains its Wanalogue and the corresponding Pr analogues (#275–278) have edge-sharing columns of (Nd,Pr) Structures #281–334 are inotellurites (Table 16, O7–8 polyhedra || x, which share a few additional deposited). The various topological types of chain edges to make pillared double layers || (001) with are summarized in Tables 2 (single chains) and 3 very large channels (14 × 9 Å) running between the (multiple chains), and depicted in Fig. 9. Our first sublayers || x. These are further linked through example is the structure of a high-temperature 5+ 6+ (Mo,W)O4 tetrahedra into a very open framework, phase of Mo5TeO 16 ≡ [(Mo2 Mo3 )O13(TeO3)] leaving small interlayer channels containing mono- (#281). As in the polymorph #168, MoO6 octa- meric TeO3 groups, while the large channels are hedra share four corners to form layers of 3-, 4- and lined by V-shaped Te5O13 pentamers (Fig. 8m). The 6-rings || (010), which then link through the

473 A. G. CHRISTY ET AL. remaining octahedral vertices to form a framework, || x, and hold the layers together. The chains are the and there is no ordering of Mo5+ and Mo6+.As structural unit, for the purposes of this classifica- before, Te is in the centre of the hexagonal ring, but tion. In [Ga2(Te2O5)(Te2O6)] (#288), the Te2O5 this time it is 4-coordinated, and shares oxygen chains are || [110]. These, and dimeric groups 4– atoms with Te of layers above and below to form a [Te2O6] , which consist of two TeO3 units linked corner-sharing chain || y. In the long-range average by a long (2.35 Å) fourth bond to Te4, cross-link crystal structure the chain is einer, but the bridging otherwise isolated GaO5 and GaO4-polyhedra into oxygen is on a twofold split site, which implies that a framework. [InF(Te2O5)] (#289) has trans-InO4F2 the Te–O–Te configuration is nonlinear and the true octahedra sharing F atoms to form a helical vierer local periodicity of a chain is at least zweier. chain || z. These are cross-linked into a framework AgTeO2(NO3) ≡ Ag2[Te2O4](NO3)2 (#282) has by Te2O5 chains, which occur in four layers per unit TeO 4 polyhedra of the type shown in Fig. 4c, cell along the z direction, and run || [110] and sharing edges to make an electrostatically neutral || [110] in alternate layers. 0 zigzag chain [Te2O4] || z (Fig. 9a). These lie in La4Ta2Te 6O23 ≡ La4[Ta2O6(Te2O5.4)(TeO3)2] – + layers || (020), with interstitial NO3 and CN6 Ag [Te2O5.6](#290) has a somewhat disordered ions, which themselves form a weakly bonded layer structure with three fundamentally distinct types + – in which Ag and NO3 are arranged respectively of Te. One type (Te3) approximates a chain of the 2+ 2– 4– like the Pb and O in the litharge form of PbO zweier CN4 type [Te2O6] (Fig. 9c) running || z. (Boher et al., 1985). Telluroperite, Pb3TeO 4Cl2,is However, the bridging oxygen atoms are only more precisely written as Pb2[(Pb0.5Te 0.5)2O4]Cl2 77–80% occupied. Another type (Te1+Te2) osten- (#283). The Te–O complex is a chain topologically sibly forms a similar chain, but the Te atoms are similar to Fig. 9a, but with square-pyramidal actually on a twofold split site and again the polyhedra (Fig. 4b) and a net negative charge due bridging oxygen sites are only partly occupied to random substitution of 50% of the Te4+ by Pb2+. (71%), implying that the Te atoms are locally in a The (Pb,Te)–O chains and the remaining Pb2+ very strongly asymmetrical 3+1 coordination cations form litharge-type layers || (002), with Cl– environment, and that the ‘chain’ is actually a anions between the layers (Fig. 29). The resulting sequence of Te2O5 dimers (58%) and orientation- 3+ structure is isostructural with perite, Pb2[Bi2 O4] ally disordered TeO3 monomers (42%). The Te 3+ Cl2, and its Sb analogue nadorite (Kampf et al., atoms of the second chain share corners with a 2010f). Rajite, [Cu(Te2O5)], has the corner-sharing parallel zweier chain of corner-sharing TaO6 chain of alternating CN3 and CN4 Te4+ seen in octahedra, which are decorated by additional Fig. 9b (#284). The chains run || x, and are made TeO 3 groups (Te4) to form a second one-dimen- from finite dimers by the rather long fourth bond to sional structural unit. All the Te lone pairs point in Te2 (2.30 Å). Chains are cross-linked into a towards the centres of large rhomb-shaped channels framework through CuO4 squares, which do not || z of a trellis-like matrix of edge-sharing LaO9 link to each other unless a fifth Cu‒O distance (also polyhedra (Fig. 29). K[(UO2)(Te2O5(OH))] (#291) 2.30 Å) is included, in which case the resulting has chains || x of Fig. 9c type, which share corners CuO5 pyramids form edge-sharing dimers. Nd with UO6 octahedra to form pleated layers || (020). [Te2O5]Br (#285) has layers || (002) of edge-sharing The layers have Te‒Te‒U 3-rings and Te‒Te‒U‒ NdO8–12 polyhedra, braced above and below by Te‒Te‒U 6-rings. The layers are held together by 2– + [Te2O5] chains || y which are topologically similar CN10 K ions, which sit at the centres of the to those of rajite, but have an unusual planar hexagonal rings.There are two types of bridging T-shaped geometry for the CN3 polyhedron. This oxygen atom in the Te chain, with different Te–O may be due to the presence of four interlayer Br– distances of 2.07 and 2.28 Å; the latter oxygen atom ions at a relatively short distance from the Te cation probably accommodates the H+. Schmitterite, (3.35–3.47 Å). The structures of the Cl analogue UO2TeO 3 ≡ [(UO2)2(Te2O6)] (#292), also has its 4– (#336) and the Ho analogue of that compound TeO 3 groups linked into a [Te2O6] chain (|| z), and (#307) are different (see below). Nd2[Te2O5] these are linked through U into a pleated sheet || 6+ (Te2O5)(MoO4) and its Pr analogue (#286–287) (010). However, the U forms edge-sharing chains have edge-sharing zigzag double chains of of UO7 polyhedra, all Te–U links are through CN3 (Nd,Pr)O8–9 || x, which are bridged via MoO4 oxygen atoms bonding to either 2Te + U or to Te + tetrahedra to form looped layers || (001). Dimeric 2U, and layers are held together only through long 2– … [Te2O5] ions (Fig. 8a) brace the layers, while Te O bonds (Fig. 29). Tl3[(UO2)2(Te2O5(OH)) zweier chains of the same composition (Fig. 9b) run (Te2O6)] · 2H2O(#293) has two symmetrically

474 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

4+ FIG. 29. Examples of structures with zweier chains of Te polyhedra (Table 16, deposited). Small spheres: O (dark pink) when not part of a polyhedron. Medium spheres: Cl (yellow-green). Large spheres: Cs (blue), La (light yellow) and Pb or Tl (grey). Polyhedra: In (pale blue), Nb (grey), Te (dark green) and U (yellow).

distinct Te2X6 chains running || z; as in #291, the a square-net layer || (010), resembling the (Nb, hydrogen atom can be located by noting the Ta)nO4n layers of #155–158. Half of the Te are in unusually long Te2–O7 distance: 2.21 Å as monomeric TeO3 groups that share additional opposed to 2.04–2.07 Å for the other bridging corners to form Nb‒Nb‒Te 3-rings that are oxygen atoms. Isolated UO7 polyhedra link the Te alternately above and below the Nb layer along chains into corrugated layers || (040), held together the x direction, while the other half of the Te form + through three kinds of Tl ion (CN = 5–9) and water zweier chains Te2O6 || z that do not connect directly molecules in the interlayers (Fig. 29). to Nb, but brace a layer of edge-sharing InO7 InNbTe2O8 ≡ In2[NbO2(TeO3)]2[Te2O6](#294) polyhedra that holds together the Nb‒Te layers. has NbO6 octahedra sharing four corners to form Thus, there are two separate structural units, a

475 A. G. CHRISTY ET AL.

Te chain and a Nb‒Te heteropoly layer (Fig. 29). so that Te has CN = 4 rather than 6, while the 0600 1411 The related compound BiNbTe2O8 ≡ Bi2[NbO2 environment of V is changed from Q to Q , (TeO3)]2[Te2O6](#295) also has corner-sharing with V making a bond to a CN3 bridging oxygen of NbnO4n sheets, but while the unshared corners are the Te chain rather than to the missing anion. The trans in #294 so that the sheets are planar, in the Bi V–O–V bridges are very asymmetrical, one compound the unshared corners are cis, and the distance being 2.24 Å while the other is 1.66 Å, sheets || (002) are strongly pleated. Again, half of almost identical to the distance between V and the + the TeO3 link to the Nb sheets, completing Nb‒Nb‒ CN1 ligand. Thus, nonlinear [VO2] complexes Nb‒Te 4-rings rather than 3-rings, this time, while can be recognized in the structure. The Tl+ ions are the rest of the Te form Te2O6 chains between the in very one-sided 7-coordination in the channels. 5+ layers, running || y. The BiO4+3 polyhedra share Polymorph II of TeO(As O3OH) ≡ [(AsOH)2 edges to form a corrugated layer that is braced by (Te2O8)] (#299), like polymorph I (#225 above), the Te chains and also links to the Te of the Nb‒Te has Te in 5-fold coordination, but the TeO5 units. Cs3[Nb9O20(Te2O6)(TeO3)2](#296) has very polyhedra now form corner-sharing zweier chains thick layers of NbO6 octahedra || (200) that are Te 2O8 || y (Fig. 9d) rather than edge-sharing dimers. 2– slices of a pyrochlore framework. Kagome layers of [AsO3OH] tetrahedra share the three unproto- 3- and 6-rings || (011) and (011) are very prominent nated ligands with the Te chains to form a in projection down z. The pyrochlore framework is corrugated layer || (002) with Te‒Te‒As 3-rings displaced by 1c on planes || (200), which breaks and Te‒Te‒As‒Te‒As 5-rings. Hydrogen bonds 2 otherwise infinite chains of octahedra running || x brace individual layers, which are held together after only four Nb atoms. These chains are through long Te···O bonds. The triclinic poly- 4+ terminated by half of the Te rather than Nb, and morph of TeO(Se O3) ≡ [Se2(Te2O8)] (#300) has the offset of the pyrochlore framework allows Te to CN5 Te in similar zweier Te 2O8 chains || x. The retain 3-fold rather than 6-fold coordination. Thus, chain backbones have the asymmetrical crankshaft the layers are not condensed any further by strong geometry of the Pb‒O chains in massicot (Hill, bonds. The other half of the Te atoms form [Te2O6] 1985). SeO3 pyramids share all corners with the Te chains which run || z in notches in the sides of the chains to make a framework with hexagonal thick layers. The Cs+ ions are in 6–8 coordination in channels || y, which accommodate the lone pairs large interstices within the layers, which are held of both Se and Te. The monoclinic (pseudo- together only through long-distance Te…O interac- orthorhombic) polymorph #301 is topologically tions (Fig. 29). CuTeO3 ≡ [Cu2(Te2O6)] (#297)isa very similar, but slight displacements of atoms polymorph of balyakinite (#117) and the high- mean that the two Te atoms of the chain repeat are pressure phase #142. In this structure, CuO4 now related to each other through a glide plane, squares form edge-sharing dimers, condensed into rather than being symmetrically independent. chains || x through a fifth Cu–O bond at 2.43 Å. The Chekhovichite, Bi2Te 4O11 ≡ Bi4[Te4O10](TeO3)4 Cu chains lie in layers || (020), which are cross- (#302) has the zigzagging vierer Te chain of Fig. 9e, linked into a framework by Te2O6 chains running || with CN3 Te at the sharp bends. The chains trend [101]. Like Cu, Te has a very irregular coordination || y, and zigzag in layers || (002). BiO7–8 polyhedra environment, with three Te–O distances of 1.87– share edges to form corrugated sheets with a 1.92 and the fourth at 2.43 Å; it has no other oxygen honeycomb net, between the Te chains, and the 5+ atoms within 2.8 Å. TlV TeO 5 ≡ Tl2[(VO2)2 monomeric TeO3 groups brace the Bi sheets. (Te2O6)] (#298) has trans corner sharing chains of Na2MoTe4O12 ≡ Na2[MoO2(Te4O10)], its W ana- distorted VO6 octahedra in a centred-rectangular logue and the corresponding Ag‒Mo compound array, running || x. These are cross-linked by Te2O6 (#303–305) have topologically similar but more chains running || z into a framework with large contorted vierer Te chains, which are cross-linked channels || x and z. The resulting three-dimensional in pairs through otherwise isolated (Mo,W)O6 net has intersecting layers of kagome topology octahedra to make looped heteropoly chains || z. || (011) and (011), like the weberite structure (Knop These chains lie in layers || (200), which are loosely et al., 1982, Fig. 14g, #672 below). In fact, the held together through CN7 (Na,Ag)+ ions. The Te framework can be derived from that of weberite by bond threshold for these structures has been set at 1a displacement of slices || (002), thus condensing 2.38 Å. If an additional bond at 2.39–2.48 Å is 2 into chains what would otherwise be isolated Te included, then Te2 atoms of neighbouring chains polyhedra, and adjusting the Te‒O‒V bonding share edges to join the chain structural units into a pattern slightly. In #298, oxygen atoms are removed continuous layer with 10-rings || (200). The

476 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

4+ FIG. 30. Examples of structures with vierer or sechser single chains or with double chains of Te polyhedra (Table 16, deposited). Medium spheres: Cl (yellow-green). Large spheres: Bi (violet) and Pb or Tl (grey). Polyhedra: Fe (orange- brown), Mn (magenta) and Te (dark green).

2+ 3+ – compound Fe8Te 12O32Cl3Br3 ≡ [(Fe2 Fe6 )(Te4O10) partly-disordered (Cl, Br) ions, and is lined by (Te2O5)2(TeO3)4]Cl3Br3 (#306) has four types of Fe Te 2O5 groups which brace the Fe layers. atom in 5 or 6 coordination, which link in a Monomeric TeO3 groups decorate the other side honeycomb net to form layers || (004). The different of the Fe layers, facing the other type of gap, but on linkage patterns for Fe1–Fe4 polyhedra are this side, the layers also link to Te4O10 chains described concisely by Q states as Q0603,Q1502, running || y, which join the Fe layers in pairs and Q1501 and Q2300, respectively. Bond-valence sums thus complete the extremely complex pillared indicate that Fe2+ is ordered at Fe3. Two types of double layer structural unit (Fig. 30). The remain- interlayer gap alternate between Fe layers. One gap ing (Cl, Br)– are in channels || y between the type contains two-thirds of the loosely bound, Te chains. The chains still have alternation of

477 A. G. CHRISTY ET AL.

CN3 and CN4 Te, but are quite different in Ca would be expected to partition strongly into the conformation from those of #302–305: they are larger 8-coordinated site, but the structure needs to helically coiled, with the sharpest bending at the be reinvestigated to confirm this. A different CN4 Te atoms rather than CN3. polymorph of Mn[Te2O5] is described as #347. In HoTe2O5Cl ≡ Ho2[Te4O10]Cl2 (#307), nearly- Despite the apparently simple formula, K2Te 2O5 cubic HoO8 polyhedra share edges to make square- (#312) has an open-branched zweier Te 4O10 chain net layers || (001); half of the Ho atoms have (Fig. 9h). The chains have a V-shaped cross- interlayer Cl as a more distant neighbour. The Ho section, run || x and pack in a herringbone fashion. layers are braced by vierer Te chains which are a They are cross-linked by undulating layers || (001) 5+ topological isomer of those in #302–306, with a of KO7–8 polyhedra. Ba2V Te 4O12(OH) ≡ different sequence of CN3 and CN4 Te atoms Ba [VO (Te O (OH))] (#313) contains yet  2 3 4 9 (Table 2, Fig. 9f ). The chains trend || [110]. Layers another Te4X10 isomer, the open-branched dreier are held together only through weak Te…Cl tellurite chain of Fig. 9i. The hydroxide group is interactions. The compositionally similar Nd com- located on the CN4 Te atom that does not have the pounds #285 and #336 have quite different branch (Te4), while a VO4 tetrahedron shares an structures. Na Te O ≡ Na [Te O ](#308) has oxygen atom with the branch Te atom (Te1). Chains 2 2 5 4 4 10  yet another isomer of Te4O10 chain, with all Te 4- run || y and lie in double layers || (101), with the coordinated, but an alternation of corner- and edge- branches directed into the interiors of the double sharing (Fig. 9g). Chains trend || [101], and are held layers. BaO8–9 polyhedra lie between the double + together by CN6–7Na ions. The arrangement of layers. (NH4)2WTe2O8 ≡ (NH4)4[(WO2)2(Te4O12)] (Na,Te) and O atoms can be described as slightly (#314) has zweier Te chains with branches attached distorted slabs || (100) of rocksalt type, alternating to CN3 bridging oxygen atoms (Fig. 9j). The with fluorite-like slabs, with there being two of chains run || y, and are cross-linked by individual each slab type per unit cell. K2Te 2O5 ·3H2O ≡ WO6 octahedra, which share four corners to form K4[Te4O10]·6H2O(#309) has similar vierer chains layers || (100) with Te‒Te‒W 3-rings and Te‒Te‒ which lie in layers || (002). The chains run in [110] W‒Te‒W 5-rings. NH+ ions are between the layers.  4 and [110] directions in alternate layers. Water NiTe2O5 ≡ [Ni4(Te6O14)(TeO3)2](#315) has loop- + molecules and CN7–8K ions lie between the branched vierer chains Te6X14, with CN5 Te at the layers. The edge-sharing Te4O10 chains of Fig. 9g nodes and CN3 Te in the loops (Fig. 9k). The chains are also found in the denningite structure of run || x, and alternate with monomeric TeO3 groups 2+ 2+ 2+ Mn Te 2O5 ≡ Mn [Mn (Te4O10)] (#310). This in layers || (002). The tellurite anions are cross- nanoporous tetragonal structure has two different linked into a framework through chains of trans types of Mn site, with coordination numbers 8 and edge-sharing NiO6 octahedra which run || y; 6 respectively, which alternate in edge-sharing micelles between these chains accommodate the Te chains || z. The Mn chains are linked to their lone pairs. neighbours by Te chains which also run || z, so Pb2Te 3O8 ≡ Pb8[Te6O16](Te3O8)2 (#316) has delineate square channels with a minimum diam- both zigzag sechser chains Te6O16 of the type eter of ∼5 Å (Fig. 30). Note that the CN6 Mn are shown in Fig. 9l, and the soro Te3O8 groups of considered to be part of the overall framework Fig. 8g. Note that the chains contain both CN3 and structural unit, while CN8 Mn is not. The CN6 Mn2+ CN4 Te, with the sharp bends at the CN3 Te atoms. may be substituted by Cu2+ to produce solid The chains and tritellurite long axes all point || x. solutions and ultimately the end-member Chains lie in double layers with Te3O8 groups 2+ 2+ Mn [Cu (Te4O10)] (#311). Although Mn-domin- between the layers, and the resulting thick sheets ant synthetic compositions have been called repeat || (002). Tellurite anions within the thick ‘denningite’, it seems likely that the mineral sheets are held together by Pb2+ ions that lie on the denningite itself has Ca replacing Mn in the outsides of the sheets, and sheets are held together 8-coordinated cation site. The type material has via long Pb…O bonds. Lead is in distorted 7‒8 composition (Ca0.60Mn0.40)[(Mn0.72Zn0.24Mg0.04) coordination with three short bonds to oxygen 2+ (Te4O10)] (Mandarino et al., 1963), and the ideal atoms (Fig. 30). The compounds M2 Te 3O8 ≡ 2+ 4+ composition is given as CaMn Te 4 O10 in the [M4(Te6O16)] with M = Mg, Mn, Co, Ni, Cu or Zn IMA (http://ima-cnmnc.nrm.se/ (#317‒322) have the spiroffite structure. No IMA_Master_List_2015-05.pdf). Although the structure refinement exists for an Fe compound refinements of Walitizi (1964, 1965) constrained with this stoichiometry, while those with M =Mn occupancies to be the same on CN8 and CN6 sites, and Zn are the minerals spiroffite and

478 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS zincospiroffite, respectively. The MO6 octahedra Fig. 10b and also by the relatively simple Te2O5 share edges and corners to make honeycomb layers single chain of Fig. 9b.TheCd‒Te compound layers || (200), and are linked into a framework by a repeat || (200), with Cl– ions in the interlayer and … different Te6X16 sechser chain in which all Te are long Te Cl bonds holding layers together. However, CN4, but edge-sharing pairs alternate with a the facing direction of the pair alternates back and polyhedron that shares only corners, at which the forth along the 28 Å c repeat (Fig. 30).  3+ chain bends (Fig. 9m). The chains run || [101] and Fe Te 3O7Cl ≡ [Fe2(Te6O14)]Cl2 (#328) and the lie in layers || (202). The trellis-like intersection Br analogue (#329)havedreier double chains pattern of M and Te layers results in 5 Å diameter Te 6O14 made out of 5-rings (Fig. 10c), flattended on channels running || y and z, which accommodate the (101) and running || y. The chains are linked Te lone pairs (Fig. 30). through edge-sharing dimers of FeO5 polyhedra to 2+ 3+ Fe3Te 4O12 ≡ [Fe2 Fe4 (Te6O18)(TeO3)2](#323) make very thick double layers || (100), which 3+ has edge-sharing dimers of Fe O6 octahedra contain channels || z. Halide ions lie in the interlayer (Fe1 = Fe3, Fe‒O = 1.94‒2.15 Å) and edge-sharing spaces, and the layers are held together only 2+ … … dimers of Fe O6 octahedra (Fe2 = Fe2, Fe‒O= through weak Te (Cl, Br) and Te O interactions. 2.05‒2.48 Å), which share CN3 oxygen atoms to Te2 in this structure has coordination that is make layers || (100). The layers are braced by TeO3 strongly 3+1: the third- and fourth-nearest oxygen monomers and linked into a framework through atoms are at ∼1.95 and 2.42 Å. If the fourth ligand open-branched vierer chains Te6O18 (Fig. 9n). The is not included, the double chain becomes a chains run || y, but zigzag || [101], obliquely to the Fe serpentine sechser single chain. Tl2Te 3O7 ≡ layers. Te3O3(PO4)2 ≡ [P4(Te6O22)] (#324) also has Tl4[Te6O14](#330) has a very different Te6O14 an open-branched vierer chain, but with CN4 and double chain which is only zweier but has the CN5 Te atoms (Fig. 9o). The chains run || z,with subchains linked through edge-sharing Te dimers branches extended in the y direction, and lie in (Fig. 10d). Thus, the subchains are open-branched layers || (200). Two types of PO4 tetrahedra share all but are linked via the branches so that the double corners with the Te chains to make a framework chain as a whole is not. The resulting ribbons are which, unusually, has no 3-rings, but does have Te‒ flattened on approximately (011) and run || x. The Te‒Te‒P and Te‒P‒Te‒P 4-rings and Te‒Te‒P‒Te‒ Te chains interpenetrate with and cross-link layers || P 5-rings. Ca4Te 5O14 ≡ Ca8[Te8O22](TeO3)2 (#325) (010) of edge-sharing TlO5 polyhedra (Fig. 30). 3+ has open-branched sechser chains (Fig. 9p) running Fe2 Te 4O11 ≡ [Fe4(Te6O16)(Te2O6)] (#331) has a || y and zigzagging in the x direction, and lying with Te 6O16 chain whose description is again dependent TeO 3 monomers in layers || (004). The chains wind on the Te–O bonding threshold. Here, we include a through a trellis-like framework of CaO7 polyhedra, fourth Te2–O link at 2.496 Å, which makes a rather which has 7 Å channels || z accommodating the simple zweier double chain of 6-rings (Fig. 10e). chain branches. Without that link to close the rings, the chain is an The next few structures have multiple chains open-branched vierer single chain. The chains are (Table 3). Interestingly, two of them are compounds flattened on (102) and run || y. The chain is with Fe3+, and two are complex compounds with Cd topologically the same as a slice of the alumino- and Cl. Bi3Te 4O10Cl5 ≡ Bi3[Te2O4](TeO3)2Cl5 silicate sheet of prehnite, Ca2[Al(AlSi3O10)(OH)2], 0 2 4 (#326) has the simple einer [Te2O4] ribbon of which has a similar alternation of Q and Q Fig. 10a, in which Q1032 Te atoms are linked through polyhedra in its 6-rings (Papike and Zoltai, 1967). CN3 oxygen atoms. These run || y, and with TeO3 FeO6 and FeO5 polyhedra share a corner to form monomers and BiO4Cl2 and BiO4Cl5 polyhedra, Fe2O10 dimers, which cross-link the Te chains, define layers || (201), with the Cl– ions in the leaving channels || y which accommodate additional interlayers. Although the Te double chain is Te in edge-sharing dimers Te2O6 (Fig. 8c). nominally neutral, in reality, Te1 makes weak Na2Te 4O9 ≡ Na4[Te8O18](#332) has a very complex bonds to Cl–, and the non-bridging oxygen is zweier double chain in which the two subchain shared with Bi1. Cd7Te 7O17Cl8 ≡ Cd7[Te5O12] backbones are linked through the familiar ‘double- (Te2O5)Cl8 (#327) has a commensurately modulated triangle’ tetrameric clusters (Fig. 10f ). These chains structure in which seven types of Cd polyhedra run || y, and their parallelogram-shaped cross-section (variously CdO3Cl3,CdO4Cl3 or CdO3Cl4) form defines the geometry of the unit cell. The chains are edge-sharing ribbons, flattened in the yz plane and held together through layers || (100) of NaO5–6 running || y. These ribbons are braced on one side by polyhedra. The K and NH4 analogues have a quite the rather complex zweier double chain Te5O12 of different layer structure (#354–355).

479 A. G. CHRISTY ET AL.

4+ FIG. 31. Examples of structures with layers of Te polyhedra (Table 17, deposited). Small spheres: N (brown) and O #340 (dark pink) when not part of a polyhedron. N and O constitute interlayer NO3 groups in . Medium spheres: Br (red). Large spheres: Bi (violet) and Li (pale blue). Polyhedra: Mo (dark grey), S (yellow) and Te (dark green).

We have two instances of chains with multipli- which share all four corners and half of which share city greater than two. Te4O5(PO4)2 ≡ [P2(PO)2 only three. Cd4Te 6O13Cl6 ≡ Cd2[Te6O13](Cd2Cl6) (Te8O24)] (#333) has the open-branched zweier (#334) contains the extraordinary quadruple chains triple chain shown in Fig. 10g. As noted earlier, the of Fig. 10h. The outer two backbones are zweier, central ribbon of 6-rings resembles that of ‘biopyr- and contain edge-sharing Te trimers surrounding a ibole’ silicate minerals such as jimthompsonite, CN3 oxygen atom, similar to those of Fig. 8i. (Mg,Fe)5(Si6O16)(OH)2 (Veblen and Burnham, Conversely, the central backbones are dreier, and 1978), except for the increased coordination are linked through shared ‘double-triangle’ clusters. number of the Q2300 polyhedra. The Te ribbons The resulting ribbons are flattened on (012) and run are run || y, and are connected to form strongly || x. They stack en échelon, and are connected into pleated layers || (201) by PO4 tetrahedra, half of layers || (001) through edge-sharing ribbons of

480 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

CdO7 and CdO8 polyhedra. Between these layers, #337 approximates Bi[Te2O5]Cl, but is more CdCl6 octahedra form edge-sharing ribbons, and accurately written Bi0.87[Te2O4.9]Cl0.87. Again, it the structure is held together by weak Te…Cl bonds. has a strongly layered structure in which Bi atoms are at the core of the layers, Te on the outsides, and weak Te…Cl bonds are holding the layers together. Structures with Te4+ complexes that are infinite However, layers have trigonal rather than (pseudo) sheets tetragonal symmetry, and there is very extensive long-range disorder. Tellurium has one apical Table 17 (deposited) lists phyllotellurites #335– ligand O1 at 2.02 Å, but other oxygen sites at 3 × 363, whose various types of Te–O sheet are 2.14 Å (O3), 3 × 2.37 Å (O3) and 3 × 2.41 Å (O2). summarized in Table 4 and shown in Fig. 11 The O2 and O3 sites are only 73% and 24% (single layers) or Table 5 and Fig. 12 (double occupied, respectively, and short O…O distances layers). Bi10Te 2O17Br4 ≡ Bi10[TeO2]2O13Br4 (#335) imply that there must be considerable short-range … has the simple, electrostatically neutral TeO2 layer order. The O3 sites occur in triangles with O3 O3 = of Fig. 11a, with square-pyramidal TeO4.Itisa 1.27 Å, so only one position out of each triplet pseudotetragonal with a ≈ b ≈ 4 Å. The Te pyr- can be occupied, and each O2 site has three O3 at amids share edges with BiO8 cubes which have 1.70 Å, so either O2 or one of those O3 positions BiO4 pyramids on the other side. The composite can be occupied. The simplest and most symmet- Bi2TeO 4 layers || (001) that are thus formed can be rical occupancy pattern which satisfies these regarded as slices of a fluorite-like structure. These constraints and approximates the refined occupies layers alternate along z with topologically similar of the average structure is shown in Fig. 11b.Each but Te-free Bi3O4 layers. In both cases, an Te atom has ligands which are 1 × O1 plus either additional ‘interstitial’ anion site, in an ‘octahedral’ 3 × O2 (¾ of the time) or 2 × O2 and 2 × O3 (¼ of interstice of the cubic close-packed cation slab, is the time). The resulting layer has 3-rings of Q1030 25% occupied by O2– to give a ‘stuffed fluorite and Q1220 Te polyhedra with the geometry of slab’ stoichiometry (Bi,Te)3O4(O0.25). These inter- Fig. 4d and a distorted variant of Fig. 4e respect- stitial oxygen atoms are weakly bonded to Bi and ively, an ideal stoichiometry Te2O5, and a within- Te, but are too far from Te (2.51 Å) to be included in layer repeat that is a 2 × 2 superstructure of the the Te–O complex of our classification. It should be crystallographic unit cell. The long-range disorder noted that short O…O distances of 2.38 Å suggest reflects at least stacking disorder of that ordering that accommodation of the additional oxygen pattern, possibly with an admixture of other short- requires adjustment to other parts of the structure. range ordering schemes. Compound #338 is Br– anions lie between the layers, which are held another Bi tellurite halide with an ostensibly together through weak Bi…Br and Te…Br interac- simple stoichiometry concealing structural com- tions (Fig. 31). NdTe2O5Cl ≡ Nd[TeO2]2OCl plexity (Fig. 31). It approximates BiTeO3Br, is (#336) is structurally very similar, although it is more accurately represented by the structural truly tetragonal, has all stuffed-fluorite formula Bi2[TeO3][TeO2]OBr2, which if partial NdTe2O4(O) layers equivalent, and thus has a occupancies are indicated becomes in turn halved c repeat. The similarity between these Bi1.93[TeO3][TeO2]OBr1.8. Like #336,itisa compounds is best seen if the formulae are tetragonal structure with a ≈ 4 Å. There is a written as [(Bi2Te)O4(O0.25)][Bi3O4(O0.25)]Br2 stuffed-fluorite compound layer (BiTe2)O4(O) and [(NdTe2)O4(O)][(NdTe2)O4(O)]Cl2. The similar to the (NdTe2)O4(O) layers of that structure fully-occupied interstitial oxygen site has 8 × O at or (BiTe2)O4(O0.25)of#335. Again, there is a fully- 2.58 Å, 4 × Nd atoms at 2.86 Å and 2 × Te atoms at occupied ‘interstitial’ oxygen site, but this is now at 2.42 Å. If these oxygen atoms were included as Te 2.87 Å from 4 × Bi, 2.59 Å from one Te and only ligands, then the Te coordination would increase 1.88 Å from the other Te atom. Thus, individual from square-pyramidal CN4 to CN5 (Fig. 4b,e), layers are polar, the Te–O complex on one side 0 and the Te–O complex would be not the single being the neutral layer [TeO2] with CN4 Te 0 [TeO2] layer of Fig. 11a, but a double layer (Fig. 11a), while that on the other side is anionic 2– 2– [Te2O5] , in which sublayers of the type shown in [TeO3] with CN5 Te (Fig. 11c). The full stacking Fig. 11c are linked by corner-sharing of the sequence includes two such fluorite-like Te1‒Bi‒ additional oxygen atoms. Note the very different Te2 slabs of opposing polarity, and also a separate chain structures exhibited by the Ho analogue Bi2O2 layer which is thinner, with a geometry more (#307) and the Br analogue (#285). Compound obviously similar to the litharge form of PbO

481 A. G. CHRISTY ET AL.

(Boher et al., 1985). Indeed, the overall structure contain uncharged Te4+−O sheets, although analo- has the same P4/nmm space group as litharge. gues are known for other p-block elements. The Bromium forms double layers between the two mineral lucabindiite, ideally K[As4O6]Cl fluorite-like slabs and also single layers between (Garavelli et al., 2013), has planar As4O6 sheets fluorite and litharge slabs; the structure is held which direct their lone pairs towards interlayers of together through weak Te…Br and Bi…Br bonds. Cl–, while the oxygens face interlayers of K+. 1+ 3+ (Cu Cl2)[Sb TeO 3](#339) has a disordered Bi4Te 2O9Br2 ≡ Bi4[Te2O5]O4Br2 (#342)isanother 50 : 50 mix of Sb3+ and Te4+ cations, which are Bi tellurite containing fluorite-like Bi‒Te‒O slabs 4-coordinated and form (Te,Sb)2O3 layers of the || (001), like #335 and #338. In this case, a and type seen in Fig. 11d, which can be generated by b ≈√2×4 Å≈ 5.6 Å, as the Te–O component condensing the double chains of Fig. 10a through layer contains alternating CN4 and CN5 Te atoms additional corner-sharing. Note that in this (Fig. 11f ), and is in effect an ordered intermediate + compound, the layers are cationic, [SbTeO3] . between the layers of Figs 11a and 11c. It should be The layers are || (201), and between them are noted that the CN4 Te atom is in almost square- intercalated 3-wide ribbons running || y of CuCln planar coordination, which is unusual, and suggests polyhedra. The outer two Cu positions form well- that some atomic coordinates may be incorrect. The ordered chains of corner-linked CuCl4 tetrahedra, (Bi4Te 2)O8(O) stuffed-fluorite slabs are polar, with while the central Cu atom is delocalized across Te on only one side. Single layers of Br– ions lie triangular 3-fold and linear 2-fold coordinated between slabs, which are linked through weak … … positions. [Te2O3OH](NO3)(#340) has corrugated Te Br and Bi Br bonds. layers || (200) of the topology shown in Fig. 11e,in In one form of Li2[Te2O5](#343; the other which Q0401 polyhedra form a 3-connected net of polymorph is #351), Q1300 Te polyhedra link to 6-rings despite having CN4, by virtue of sharing form layers of 6-rings, topologically equivalent to one edge. The Te atoms and O1, which does not the silicate sheets of the ‘micas’ (Fig. 11g). participate in the shared edge, form corner-linked Resemblance to micas is further enhanced by the chains of massicot-like asymmetrical crankshaft fact that such sheets occur in pairs, and their apical geometry running || z (cf. Hill, 1985). Te–O oxygen atoms are directed inwards, towards a distances for O1 (1.89 + 2.05 Å), O2 (2 × 1.93 Å) ‘sandwich filling’ layer of electropositive cations. and O3 (2 × 2.17 Å) indicate unambiguously that In this compound, however, the core of the layer is the H atom is attached to O3. The resulting layers composed of tetrahedrally coordinated Li+ cations, + are again cationic, [Te2O3OH] , and are held rather than higher-valence species in octahedral together through their electrostatic attraction to coordination. The compound mica-like layers are –  interlayer NO3 anions (Fig. 31). A layer of the || (101), with Te lone pairs directed into the interlayer Fig. 11e topology also occurs in the mineral gap and only weak Te…O bonds connecting layers tellurite, an orthorhomic polymorph of TeO2 (Fig. 31). (Te2O3)(SO4) ≡ [(SO2)(Te2O5)] (#344) (#341), where very tightly corrugated layers of also has phyllotellurite sheets || (010) with the this type are || (200). These layers are electro- topology of Fig. 11g, but the non-bridging oxygen statically neutral, and are held together only by long atoms are not all on one side of the sheet. Te …O bonds. It should be noted that the structure is Hexagonal rings are bent in a boat configuration, isopuntal with the brookite polymorph of TiO2, but and pairs of apical oxygen atoms point alternately whereas the Ti atoms of brookite have six oxygen up and down along y. All ‘up’ or ‘down’ pairs have neighbours at 1.863–2.052 Å (Meagher and Lager, Te–Te || x, and individual 6-rings have either four 1979), the lone-pair stereoactivity of Te4+ distorts ‘up’ polyhedra and two ‘down’ or vice versa the coordination octahedron to give only four (Fig. 31). This is an analogue of the silicate sheet neighbours in the range 1.88–2.20 Å, an additional found in sanbornite, Ba[Si2O5] (Hesse and Liebau, neighbour within the layer at 2.64 Å, and a weak 1980), rather than the mica structure type. Each pair Te–O bond across the interlayer gap at 3.07 Å. of apical oxygen atoms is shared with a SO4 A variant of the structure with additional anion- tetrahedron, thus completing the heteropoly layer anion bonding occurs for the pararammelsbergite structural unit. Layers are held together through form of NiAs2 (Fleet, 1972) and intermetallic long bonds between the Te of one layer and the non- compounds such as AuSn2 (Rodewald et al., 2006). bridging sulfate oxygen atoms of the next. Tilt of Two other polymorphs of TeO2 are discussed as the SO4 groups and asymmetry of the Te–O–Te #364–365 below. At present, there do not appear to angles make the structure polar || z. The layer be examples of more complex structures that || (010) of (Te2O3)(PO3OH) ≡ (POOH)[Te2O5]

482 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

4+ FIG. 32. Examples of structures with layers or frameworks of Te polyhedra (Tables 17–18, deposited). Small spheres: O (dark pink) when not part of a polyhedron. Large spheres: Ca (orange), K (purple) and Pr (pale yellow). Polyhedra: Fe (orange-brown), Te (dark green), U (yellow) and Zn (pale grey).

(#345) also has pairs of ‘up’ or ‘down’ Te polyhedra, parameters of these two structures are very similar, buteach6-ringhasthreeofeach,andthe‘up’ (or reflecting the similarity of layers and their stacking. ‘down’) pairs are arranged in a herringbone pattern. [Mg(Te2O5)] and the β polymorph of [Mn The PO3OH tetrahedra again share two corners with (Te2O5)] (#346–347) have layers || (020) with adjacent Te polyhedra of a layer. Interatomic 6-rings of the ‘four up/two down’ type, like #344, distances indicate that the H atom is attached to the but the 6-rings are distorted so that ‘up’ Te–Te pairs non-bridging phosphate oxygen atom O7, and forms point along [102] while ‘down’ pairs point || [102]. hydrogen bonds that brace the layer, rather than Layers are cross-linked into a framework through connecting between layers. Layers are connected by zigzag edge-sharing chains of MO6 octahedra (M = weak bonds between Te and the other non-bridging Mg or Mn). The octahedral chains run || z, with phosphate ligand O5, and the overall structure is small channels between them that can accommo- polar || z for the same reasons as #344.Theb date the Te lone pairs. The ‘denningite’ polymorph

483 A. G. CHRISTY ET AL. of the Mn compound was discussed above (#310). of Te polyhedra; however, the latter are now 3- 0401 MoTe2O7 ≡ [(MoO2)(Te2O5)] (#348) also has ‘four connected Q type, as seen in Fig. 11k. The up/two down’ layers, this time || (002), but the layers layers are crumpled and rather thick, with the edge- are strongly pleated so that the Te–Te pairs point sharing Te=Te vectors almost normal to the overall obliquely to the overall trend of the layer, || [232] layer plane (100). Layers are linked through sheets  (‘down’ pairs relative to +z)or[232] (‘up’). Layers of CaO7 polyhedra (Fig. 32). Note that this contain very obvious massicot-like Te‒O‒Te‒O description requires a slightly longer than usual chains || x. Tellurium layers are linked into a strong-bonding distance threshold; if a Te–O framework through MoO6 octahedra chains, which distance of 2.450 Å is not included, the layer occur as edge-sharing Mo2O10 dimers which then breaks up into finite Te4O10 tetramers of the type share four additional corners to make ladder-like seen in Fig. 8j, #250–255. A similar topology of double chains || x (Fig. 31). layer, less tightly corrugated, occurs || (101) in La2[Te3O7]2(WO4)(#349) has the unique layers Tl2[Te2O5](#353). Layers are linked through very of 3- and 6-rings shown in Fig. 11h; note that the irregular TlO5–7 polyhedra. K2[Te4O9](#354) and + node where three 6-rings join is a CN3 oxygen its NH4 analogue #355 are isopuntal, but giving atom. These layers are || (002), and the non- them a common description again requires a careful bridging oxygen atoms of the Q1210 Te polyhedra choice of Te–O bonding threshold, which is 2.43 Å all point inwards from two such layers towards a here. This excludes additional neighbours at 2.433 central sheet of LaO10 polyhedra. Between the and 2.489 Å to respectively Te1 and Te2 of the K 6-rings of the two Te sheets are large interstices compound, which are at 2.713 and 2.615 Å and which contain WO4 tetrahedra, disordered between hence clearly not strongly bonded in #355. The 3+ ‘up’ and ‘down’ orientations. Mackayite, Fe convoluted Te8O18 layers || (100) in these structures (Te2O5)(OH) (#350) has layers that should be have the topology of Fig. 11l, with 6- and very written Te4O10 to reflect the translational period- elongated 14-rings containing both CN3 and CN4 icity. These have 4- and 8-rings similar to the Te polyhedra. The layers are held together by large ‘apophyllite’ type, as seen in Fig. 11i. In the cations, 7–8 coordinated by oxygen in the case of mackayite layer, individual ‘upward’ and ‘down- K+. This structure is very different from the double- ward’ pointing polyhedra alternate, unlike apophyl- chain type of the Na analogue (#332, Fig. 10f ). lite, where whole 4-rings of ‘up’ and ‘down’ Although K2[Te4O9] · 3.2H2O(#356) is triclinic, it tetrahedra alternate (Colville et al., 1971). The is strongly pseudohexagonal (b ≈ c, α ≈ 60°) and layers lie || (004), repeated by a screw tetrad axis. has rather symmetrical Te8O18 layers || (100) The layers are held together by edge-sharing dimers containing two types of 6-ring (Fig. 11m). One of Fe octahedra, Fe2O8(OH)2 (Fig. 32). Our second quarter of the rings are regular containing polymorph of Li2Te 2O5 ≡ Li4[Te4O10](#351) like only CN4 Te, with non-bridging ligands pointing its dimorph #343 has Te layers || (020) in which all alternately ‘up’ and ‘down’. The rest of the rings are Te are CN4; however, the polyhedra form 10-rings, elliptical, and three of these meet at a CN3 Te atom. and some of them are only 2-connected, occurring Between the Te layers are a central plane of water as edge-sharing Q1301 pairs rather than the Q1300 molecules and K+ ions in 7–8 coordination polyhedra typical of silicate-like sheets (Fig. 11j). (Fig. 32). (NH4)Rb[Te4O9]·2H2O and the corre- The edge-sharing dimers act as bridges between sponding compound with Cs replacing Rb (#357– bands where the other Te tetrahedra point downards 358)havearathercomplexTe16O36 layer (Fig. 11n). and bands where they point upwards. The pointing The layers are || (002), and can be regarded as formed direction reverses every 1c. Tellurium sheets are held by condensation of Te O clusters. The clusters, in 2 8 20 together through the non-bridging oxygen atoms, turn, consist of a central edge-sharing pair of Q0501 whichlinktoLiO4 tetrahedra, which occur as pairs Te atoms, common to two 4-rings which are each 1300 of vierer corner-sharing helices (cf. Li2[TeO3], #1) completed by a pair of Q Te atoms, each 4-ring in running || x between Te layers. The regular turn sharing one side with a 3-ring formed by links to inversion of pointing direction in the Te layers, aQ0300 Te atom. The remaining corners of the and breakup of the Li component into discrete 4-rings and the CN3 Te atom of the 3-rings then link ribbons, gives this structure a resemblance to to other clusters to make a continuous layer, which commensurately modulated phyllosilicates such has very elongate 12-rings. Large cations and water as sepiolite, Mg4[Si6O15](OH)2 ·6H2O(Post molecules are between the layers. et al., 2007). The Te4O10 layer of Ca[Te2O5] Our final single-layer structure, Ba6[Te10O25]Br2 (#352) also has 10-rings and edge-sharing dimers (#359), also has an extraordinarily complex layer

484 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

with a translational repeat Te40O100 and ten symmet- The structure of the paratellurite polymorph of rically distinct types of Te (Fig. 11o). The layers are || TeO 2 (#364, Fig. 12c) is derived from that of the (002) and are rather thick but looped rather than rutile form of TiO2 (cf. Meagher and Lager, 1979) double, with tubular cavities running || x which in a way analogous to the derivation of the tellurite contain the Br– ions. Ba2+ cations between the layers structure from brookite (#341 above). The lone-pair link to 8–9 O atoms of the tellurite layer and 0–1Br. stereoactivity of the Te4+ changes the coordination Again, the layer is most simply described if an environment from the relatively regular octahedron unusually long bonding threshold of 2.52 Å is used. of rutile to a strongly distorted 4 + 2 pattern with This includes all the moderately strong Te–O bonds: 2 × O at 1.88 Å, 2 × O at 2.12 Å and 2 × O at 2.87 Å. seven out of the ten Te sites have oxygen neighbours However, unlike tellurite, the lengthening and in the 2.41–2.52 Å range, while none have any other weakening of two bonds per Te atom does not neighbours within 2.98 Å. With the Te–Obond disrupt the framework of the TiO2 aristotype. network thus defined, Te are CN4 (Te1 Te2, Te4 = However, the tetragonal c repeat is doubled, and 0400 1300 2200 Q ,Te9=Q and Te5–Te8 = Q ) except Te3 the 42 screw axis of rutile becomes a 43 (or 41) axis (Q0300). Two types of tube alternate, both with in paratellurite. Paratellurite is ∼4.5% denser than flattened elliptical cross-sections. The denser type tellurite. Interestingly, not only is the structure a contains a ribbon of 4-rings (Te2‒Te9‒Te2‒Te9) and distortion of the rutile structure, but it is isopuntal 8-rings (Te2‒Te3‒Te1‒Te9‒Te2‒Te3‒Te1‒Te9), and topologically equivalent to the metastable with arches of three additional Te atoms completing low-temperature α-cristobalite form of SiO2 (cf. 7-rings (Te4‒Te8‒Te7‒Te3‒Te2‒Te9‒Te1). These Downs and Palmer, 1994). This suggests that the tubes are linked into a layer through Te10 and paratellurite geometry provides a pathway for bridges ‒Te5‒Te6‒ but the second type of tube diffusionless structural transformation of the type defined by those is much more sparsely connected, discussed by Christy (1993), between the relatively its smallest rings having 9 and 10 members. low-density cristobalite structure type (stable at 2+ The compounds [M (Te6O13)] (M = Zn, Fe and relatively high temperature and low pressure in the Mg; #360–362)haveTe6O13 double layers SiO2 system, for instance) and the high-density (Fig. 12a). These stack || (003) and are linked rutile type (stable at very high pressure for SiO2,as through corner-sharing with MO6 octahedra. The stishovite). At high pressure (∼0.95 GPa), para- individual sublayers contain triplets of Q0311 Te1 tellurite undergoes a continuous, displacive phase sharing a common CN3 oxygen atom, connecting to transition to a topologically similar but ortho- 1300 3-rings of Q Te2 so as to form crumpled rhombic variant TeO2-γ, whose structure has been 12-rings of Te1 and Te2, which surround the M refined at 1.98 GPa (#365). Paratellurite and the cations. Two such sublayers are linked by their Te1 high-pressure phase are isostructural with, respect- 4+ atoms sharing an edge (Fig. 32). (Te3O5)(Se O3) ≡ ively, the β and γ phases of SnF2, as noted by Denes [(SeO)2(Te6O14)] (#363) has a double layer || (001) et al. (1980), who also discuss transformations with three types of Te polyhedron: Q0300,Q1300 and involving the cristobalite and rutile structures. 1400 Q (Fig. 12b). Each sublayer has a net of 3- Pr2[Te2O6]O (#366) has a structure of the well- connected 8-rings, with CN4 and CN5 Te atoms at known pyrochlore type, which can be derived from a the nodes and CN3 Te making two links within the 2 × 2 × 2 block of face-centred cubes of the fluorite sublayer. These links result in smaller 4- and 6-rings structure by slight displacement of ¾ of the anions so that are shared by the sublayers. Two such sublayers that half of the cations are in octahedral coordination are held together by links between CN3 Te of one by them, forming a continuous framework and CN5 Te of the other. The SeO3 pyramids are on (Fig. 12d) and omission of half of the remaining the outside of the double layer, sharing one oxygen anions. The overall stoichiometry is A2[B2X6]Y, atom with CN5 Te and one with CN4 Te. Layers are where the larger cation type A is coordinated by held together by weak Te…O and Se…O bonds. 6X +2Y while B bonds to 6X only. In this case, B is Te 4+, which unsually is in rather regular octahedral coordination by oxygen, with no lone-pair stereo- Structures with Te4+ complexes that are infinite activity (Fig. 32). The next few structures are also frameworks fluorite derivatives. K[Ga(Te6O14)] (#367)hasa 1 similar-sized a ≈ 11 Å cubic unit cell to #366,but /8 + 1 Tectotellurite structures #364–375 are listed in of the cations are 8-coordinated K , /8 are 6- Table 18 (deposited), summarized in Table 5 and coordinatedGa3+, andtherest are 4-coordinated Te4+. have their Te–O frameworks depicted in Fig. 12. The K, six Te and Ga are arranged in the LiCa6Ge

485 A. G. CHRISTY ET AL.

4+ FIG. 33. Examples of structures with frameworks of Te polyhedra (Table 18, deposited). Large spheres: Pb (dark grey). Polyhedra: Sn (pale blue) and Te (dark green).

pattern (Pavlyuk et al., 1993), a superstructure of the (#374) has a tetragonal unit cell with the a parameter common Cu3Au type (Kear and Wilsdorf, 1962). similar to that of #366–373 but c about twice as 1 Relative to fluorite, /8 of the anions are missing, as large. The Cs and Te atoms form two cubes of the for pyrochlore. The remaining anions are of three MgCu2 Friauf-Laves structure arrangement (Friauf, types, bonded respectively to 2Te + K, Te + Ga and 1927; Hyde and Andersson, 1989). That is, they are 3Te + K. If we consider only the Te–Osubstructure, geometrically equivalent to, respectively, the D and 1210 it has Te6O14 stoichiometry and Q Te polyhedra T cubic lattice complexes of Fischer and Koch forming the complex network shown in Fig. 12e. (2006). This is also the pattern of Mg and Al atoms The Ga octahedra reinforce this framework. in normal spinel, MgAl2O4,andofYB2 atoms in the 4+ Cliffordite, [(UO2)(Te3O7)] (#368), has Te and A2B2X6Ypyrochlore structure. However, whereas the 6+ U in a 3 : 1 ratio, ordered in the Cu3Au B cations of the pyrochlore framework are linked arrangement like Te and (K+Ga) of #367 (Fig. 32). through X to six B neighbours (cf. #366 above), the As for that structure, the Te–OframeworkhasQ1210 Te atoms of #374 are bonded to only a subset of 0400 Te polyhedra and Te6O14 stoichiometry, but the these: half of them are CN4 (Q ) and the other 1300 topology is different (Fig. 12f ), and whereas TeO4 half are CN3 (Q ). There are no 3- or 6-rings, as in polyhedra share corners with GaO6 octahedra in the pyrochlore framework: every CN3 Te atom is a #367, they share edges with UO8 bipyramids in member of one 4-ring, while the CN4 atoms join two cliffordite. Note that the total anion content is higher such rings, and the next-smallest rings have 8 than that of fluorite: while the oxygen members (Fig. 12h). Vacant sites which would be positions and those of the oxygen atoms that link occupied by oxygen atoms in a pyrochlore allow a U to Te can all be derived by small displacements more open framework, with rather large interstices to from their counterparts in the fluorite aristotype, this accommodate Cs+ ions in 9–10 coordination. is not true for O5 of cliffordite, which joins 3 Te. Pb[Te5O11] has a very complex, open framework Very closely related is the winstanleyite structure with five symmetrically different types of Te atom 4+ type of compounds [A (Te3O8)] (#369–373), where (#375). If Te–O distances out to 2.45 Å are included 3+ A = Ti in the mineral winstanleyite (#372), (Fe0.67 as bonds, then the topology is as seen in Fig. 12i. 6+ 0312 1210 Te 0.33) in walfordite (#373), and Sn, Zr or Hf in Te1, Te2 and Te3 (respectively Q ,Q and synthetic analogues (Fig. 33). Again, Te and A atoms Q0401) form complex double chains that run || [110] are in the Cu3Au pattern. The oxygen atoms of the at z = 0 and || [110] at z = ½. These are in turn made fluorite aristotype are all present, but are displaced so from Te3=Te1=Te1=Te3 tetramers which are joined astoformquiteregularoctahedraaroundtheAcations by Te2, which shares a CN3 oxygen with 2Te1 and a and the common ‘folded rhombus’ arrangement of CN2 oxygen with Te3 (Fig. 33). Between these Fig. 4c aound Te. The Te polyhedra are Q2020,and double chains, Te4 and Te5 (both Q1300)form form a framework (Fig. 12g) where the non-bridging massicot-like single chains (cf. Hill, 1985) which ligands share corners with A octahedra. Note that for run || y at z = ¼ and ¾. The component chains are taxonomic purposes, the minority Te6+ content of joined in three dimensions byTe4 linking to Te3 on the A sites of walfordite is ignored. Cs2[Te4O9] one side of these chains, while Te5 links to Te2 on

486 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

6+ FIG. 34. Examples of structures of Te (OH)6 adducts (Table 19, deposited). Small spheres: C (black), H (pale pink), N (brown) and O (dark pink) when not part of a polyhedron. Large spheres: K (purple). Horizontal lines in #402 indicate 5+ − planes of oxygen triangles of pyramidal I O3 anions; I atoms are not shown. Polyhedra: P (brown) and Te (dark green).

the other. Lead atoms are in 8-coordination between bonding must be weak, so the compound Te(OH)6 the massicot-like chains. has discrete octahedral molecules which are held together only through hydrogen bonds. Unsurprisingly, it is hygroscopic, extremely 6+ Te (OH)6 and its adducts water-soluble, and unknown in minerals. As the Our first examples of Te6+ compounds are poly- molecule has six oxygen atoms, each of which morphs and derivatives of orthotelluric acid, Te6+ carries one donor H atom and is able to accept low- (OH)6. The large valence (∼1 vu) of bonds to O valence bonds from other electron donors outside from both Te and H means that any additioanl the molecule, Te(OH)6 is able to co-crystallize with

487 A. G. CHRISTY ET AL. a wide range of other compounds to form adducts. tetrahedra of four Cl. (RbCl)3 · [Te(OH)6](#381) The other components may be polar organic has a quite different rhombohedral structure in molecules, simple salts of large cations such as which Te(OH)6 octahedra alternate with Cl3 alkali halides, or salts with larger and more triangles to form rods || z which are linked complex anions such as polyphosphate species. through Rb, with each Rb having five Cl neigh- These adducts are physically and crystal- bours and vice versa. chemically distinctive enough that they are con- Na2(SO4) · [Te(OH)6](#382) has a unique 6+ sidered separately from other Te compounds. In structure in which Te(OH)6 octahedra form a many cases, small tilts of Te octahedra or changes to primitive hexagonal array, and alternate trigonal the H-bonding pattern may result in very similar prisms of such molcules contain either two Na or molecular arrangements occurring in a range of SO4 tetrahedra. The pseudohexagonal layers of Te different space groups and unit-cell shapes. The are || (002), with layers of Na and SO4 groups TeO 6 octahedron (Fig. 4h) is always rather regular, between them. One type of Na bonds to only two with Te–O = 1.90–2.07 Å, corresponding to bond SO4 while the other type bonds to three SO4, and valences of 1.04–0.77 vu using the parameters of their arrangement makes the structure polar in the Mills and Christy (2013). The individual structures (010) plane. There are a very large number of #376–431 are listed in Table 19 (deposited). adducts of the type A2(TO4) · [Te(OH)6], with The cubic polymorph of [Te(OH)6] itself has the larger cations A = (K, Rb, Cs, Tl and NH4) and molecules packed in a fcc array, but with the T = (S or Se) (#383–398). Despite the apparent octahedra tilted and hydrogen bonded so that the diversity of symmetries and cell parameters, all of cell repeat is doubled to 15.71 Å, and the space these are again based on a fcc array of Te(OH)6 group is Fd3c (#376). There is also a monoclinic molecules, with the tetrahedral anion occupying polymorph (#377), where Te…Te distances shorter octahedral interstices and the A cations occupying than 6.3 Å define 12 nearest neighbours in a tetrahedral interstices. The edges of the pseudo- monoclinically sheared face-centred cube, with cubic cell have different indices depending on the pseudocube edges || [100], [101] and [010] of the axial setting chosen by authors, as follows. P2 /n cell. (NaF) · [Te(OH) ](#378) retains a fcc K (SO ) · [Te(OH) ](#383) has space group P1, 1 6 2 4 6  arrangement of Te(OH)6 molecules, albeit with with pseudocube edge vectors are ½[111], ½[311] rhombohedral distortion. Na+–F– ion pairs occur in and ½[131]. The monoclinic structures with space the octahedral interstices between them, so that group C2/c, Cc, P2 /a, P2 /c, P2 /n or Pn all have 1 1 1  (NaF) units and Te(OH)6 molecules form a rocksalt pseudocube edges ½[101], ½[121] and ½[121] arrangement. Similarly, (KF)2 · [Te(OH)6](#379) (#384–390 and 392–397) except for (NH4)1.16 + – has K –F ion pairs in the tetrahedral interstices of K0.84(SO4)·[Te(OH)6](#391), which was published an orthrohombically distorted fcc array of Te(OH) in a different axial setting where the pseudocube 6  molecules, so that (KF) and Te(OH)6 are arranged edges are ½[102], ½[120] and ½[120]. Note that like F and Ca of the fluorite structure (Fig. 34). these structures include centrosymmetric and Such ion pairs are almost unknown in mineral acentric polymorphs of K2(SeO4) · [Te(OH)6] 2+ 2– structures, although the Ca –CO3 pair occurs in a (#384 and 385), structures in which two A species matrix of H-bonded water molecules in ikaite, occur in solid solution and others in which they are CaCO3 ·6H2O (Swainson and Hammond, 2003) ordered, such as CsK(SO4) · [Te(OH)6](#397), and and hsianghualite, (LiF)2Ca3[Be3Si3O12], can be that there may be one or two symmetrically distinct + – regarded geometrically as having ion pairs Li –F types of Te(OH)6 octahedron per unit cell. + replacing the Cs of , Cs23[Al2Si4O12], Cs2(SO4) · [Te(OH)6](#398) has a rhombohedrally or water of , (H2O)2(Na2)[Al2Si4O12] distorted structure, in which the pseudocube edges (Rastsvetaeva et al., 1991). However, the bond are ⅓[221], ⅓[421] and ⅓[241]. Hydrogen ions distances and the parameters of Brese and O’Keeffe may be quite mobile in these compounds; Dammak (1991) indicate that the Li–F bond is not unusually et al. (2005) investigated the protonic conductivity strong, bond valences being ∼0.25 vu for all bonds behaviour of Cs0.86(NH4)1.14(SO4) · [Te(OH)6], from Li to F + 3 O and to F from Li + 3 Ca. which has the P21/c variant of the structure but Alkali halide adducts with larger ions do not has been excluded from this study because of some have ion pairs intercalated into a matrix of fcc Te unrealistically short Te–O distances in the refinement. (OH)6. (CsCl)2 · [Te(OH)6](#380) has Te and Cl K2(NO3)2(H2O)2 · [Te(OH)6](#399) has a forming an array of monoclinically distorted CaCl2 layered structure || (001) not unlike that of #382, (or collapsed rutile) type, with Cs located in in which Te octahedra form a monoclinically

488 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS sheared primitive-hexagonal array with trigonal This compound has a rather simple structure in prisms containing the other components. which each Te octahedron has four neighbours at Conversely, (Cs3.5Rb0.5)(SeO3)1.7(SO3)0.3 ·[Te 5.1–6.6 Å, in a monoclinically distorted version of (OH)6]3 (#400) has the familiar fcc array of Te, the diamond arrangement. Each Te octahedron also although this time, large cations occupy only ⅔ of has four nearby urea molecules (Te…C = 4.2–4.5 Å), the tetrahedral interstices, pyramidal anions are in and with them defines dense layers in the structure || the other ⅓ of the tetrahedral voids, and the (202). Hydrogen bonds link molecules both within octahedral positions are empty. The pseudocubic and between these layers (Fig. 34). edge vectors are [010], ⅙[203] and ⅙[203] of the A few additional compounds containing Te orthorhombic cell. The iodate adducts all have (OH)6 molecules as hydrogen-bonded adducts layered structures. K(IO3) · [Te(OH)6](#401) has along with other Te in other environments are K+Te and I layers alternating || (001), while included below at #498–502, 504 and 631. K2(IO3)2 · [Te(OH)6](#402) has thicker layers I‒K‒Te‒K‒I || (003), with the lone pairs of I5+ 6+ cations directed into the interlayer gap (Fig. 34). Monomeric Te Xn anions (n = 4–6) (NH )(IO )(H O) · [Te(OH) ](#403) has layers of 4 3 2 6 Te 6+X and Te6+X Te + I alternating with NH +H O || (200). 4 5 4 2 Te 6+ almost always occurs in octahedral coordin- A very large number of adducts have been made ation with oxygen, as noted above and by Mills and that contain phosphate anions, along with large Christy (2013). However, we have a very small cations Na, K, Rb, Ag, Tl or NH . The phosphate 4 group of compounds in which the coordination groups range from tetrahedral monomers 2– – #404–412 number is 4 or 5. Ligands distribute themselves [PO3OH] or [PO2(OH)2] ( ) through 6+ 3– 2– symmetrically around the closed-shell Te cation, diphosphates [P2O6OH] or [P2O5(OH)2] 4+ 3– unlike the situation with Te , which usually has a (#413–415), cyclo triphosphates [P3O9] (#416– 422 4– #423–424 6– #425–427 strongly stereoactive lone pair of electrons. The ), [P4O12] ( ), [P6O18] ( ), 6+ – – coordination polyhedron for CN4 Te is a [P O ]8 (#428–429) and even [P O ]12 (#430). 8 24 12 36 tetrahedron (Fig. 4f ), while that for CN5 Te6+ is a Most of these compounds have layered structures trigonal bipyramid (Fig. 4g). Cs [TeO ](#432) has with large unit cells, mainly of low symmetry, and 2 4 the K SO -β structure, in which Te and Cs form the will not be discussed in detail here. However, we 2 4 same arrangement as Pb and Cl in cotunnite, PbCl note that K Na (P O ) · [Te(OH) ] has mono- 2 3 3 3 9 2 6 (O’Keeffe and Hyde, 1985) (Fig. 35). Cs K [TeO ] clinic and rhombohedral dimorphs (#420‒421), 2 2 5 (#433) has a tetragonal structure in which TeO with alternation of (pseudo)hexagonal layers of Te 5 polyhedra are linked through CN6 K+ and CN6–8 + P and Na + K || (200) and (003), respectively. Cs+.Rb[TeO ][TeO ](#434) contains both types Most of the phosphate adducts are crystal- 6 5 4 of Te polyhedron. In this compound, Rb and Te chemically unique: there are few examples of together form an approximately cubic close-packed more than one compound sharing the same array with pseudocube edge vectors [½00], [0½0] stoichiometry, and even when they do, the and [¼0½] of the monoclinic cell. atoms structures are different. Thus, despite the apparent are in 6–8 coordination by oxygen (Fig. 35). Note chemical similarity, (NH ) (P O )(H O) ·[Te 4 4 4 12 2 2 that in all these structures, the counterions are large, (OH) ] and its K analogue (#423‒424) are not 6 weakly-bonding alkali metal species. Details for isostructural, and the same is true for these structures are summarized in Table 20 (NH ) (P O )(H O) · [Te(OH) ] and the corre- 4 8 8 24 2 2 6 (deposited). sponding K compound (#428‒429). The most complex phosphate adduct, (C(NH2)3)12 (P12O36) 6+ (H2O)24 · [Te(OH)6]12 (#430), has as a counterion Monomeric Te X6 that are not part of a larger not an alkali metal cation but guanidinium, [C structural unit. + 6+ (NH2)3] . This compound has six Te layers and Although Te occurs almost exclusively in one three polyphosphate layers in its rhombohedral cell type of coordination polyhedron, and the range of with c ≈ 51 Å. The threefold rotational symmetry is Te–O polymers that it forms is very restricted inherited from the Te octahedra, triangular planar compared with Te4+, the monomeric tellurate guanidinium complexes and cyclophosphate rings octahedron TeX6 is the single most prolific (Fig. 34). The final adduct described here also has a structure-forming Te–O complex in the present small organic molecular component, the neutral study: there are 172 compounds with such urea molecule in (CO(NH2)2)2 · [Te(OH)6](#431). octahedral anions (#435–616 below), in addition

489 A. G. CHRISTY ET AL.

2– – to the 56 adducts of neutral molecular Te(OH)6 that long-range order of O and OH , and is thus 2+ 4+ were briefly described above. Nesotellurates up to isotypical with wickmanite, Mn [Sn (OH)6] and #456, with no larger structural unit including a family of related hydroxostannates, germanates strongly-bonding non-Te cations, are listed in and antimonates, including several mineral species Table 20 and described here. (Basciano et al., 1998). Because of nonlinear M‒ (NH4)2[TeO2(OH)4](#435) has a simple structure O‒M′ links and orientational order of O‒H groups, in which Te octahedra form a centred regular net in these compounds do not have Fm3m symmetry but   layers || (001), with layers of NH4 cations between either Pn3m (Strunz and Contag, 1960), Pn3 them. The Te–O distances show that the unproto- (Morgenstern Badarau and Michel, 1976; Cohen- nated oxygens (O1) are ordered in trans positions in Addad, 1977; Basciano et al., 1998) or P42/n the octahedron, with O‒Te‒O vectors || [201]. (Mikhaylov et al., 2011; Kleppe et al., 2012; K3Na2Li[TeO6](#436) has layers of K alternating Lafuente et al., 2015). Na[TeO(OH)5] may either be with layers of Na+Li+Te || (020). Within the latter orientationally disordered, or may actually crystal- layers, TeO6 octahedra and LiO4 tetrahedra form lize in one of these lower symmetry space groups. edge-sharing chains || [101], alternating with chains The ReO3 and wickmanite structure types are of NaO5–6 polyhedra. The three types of K atom are derivatives of the ABX3 perovskite type in which in 6–8coordination.K3Li3[TeO6](#437), somewhat large cations A are absent, leaving only octahedrally similarly, has alternation of K and Te+Li layers || coordinated species B. Many other perovskite- (200). Within the Te+Li layers, chains || y of corner- related tellurates are described below (#562–584), linked LiO4 tetrahedra alternate with chains of edge- while here, we include two unusual examples sharing TeO6 octahedra and unusual square-planar which have large cations in both A and B positions. LiO4 groups. The Li‒O distances in the distorted These are Sr3[TeO6] and Ba3[TeO6] (#442‒443) tetrahedra are 1.94–2.05 Å; those in the squares are whose unit cells are very large superstructures of similar, at 2.01–2.11 Å, with no additional O the basic perovskite cube (the cells reported are neighbours until two at 3.27–3.29 Å, which complete respectively 4 × 4 × 4 and √20 × √20 × 8 of the a very elongated octahedron around Li. Potassium is ∼4 Å cube), with rather low symmetry: the triclinic 8–9coordinated.K4Na2[TeO6](#438) has K layers structure of #442 has eight distinct Te sites, four alternating with Te+Na || (001). The Te form a face- ‘B-type’ Sr sites and eight ‘A-type’ Sr, while for centred rectangular net, and NaO6 octahedra share two #443, which is tetragonal, the corresponding opposite faces with neighbouring TeO6 octahedra to numbers of distinct sites are five, five and 13. complete the layer. Potassium coordination is 6–8. Substantial rotations of TeO6 octahedra allow some The structure of KNa5[TeO6](#439) is best ‘B-type’ (Sr,Ba) to increase their coordination described as having cations in a hcp array, with number from 6 to 7 (Sr) or even 8 (Ba). layers of composition KNa3 and Te(Na0.670.33)3 Rhombohedral Li6[TeO6] and Tl6[TeO6](#444‒ alternating along z, and two of each layer type per 445) are isopuntal, even though the great difference cell. Oxygen atoms are all equivalent and in in size and stereochemistry between Li+ and Tl+ octahedral interstices in the cation array, coordi- means that their coordination environments are nated by Te + K + 2Na + 2(Na0.67). The coordin- rather different. These compounds have defect ation environments for all alkali cations are slightly superstructures of rocksalt, in which (Li,Tl) and Te unusual: trigonal prismatic for K (K–O = 2.79 Å), are ordered on a ccp array. In #444, oxygen atoms 7 square planar for partially occupied Na1 and square occupy /8 of the octahedral interstices. Tellurium pyramidal for fully occupied Na2 (Na–O = 2.35 Å has six oxygen neighbours at 1.93 Å, Li has four at in both cases), while Te is in very regular octahedral 1.94–2.08 Å and one at 2.37 Å, and oxygen is coordination with Te–O = 1.94 Å (Fig. 35). K[TeO surrounded by Te + 5Li. In the Tl compound, the (OH)5]·H2O(#440) has KO9 polyhedra sharing inter-cation distances and cell parameters are much edges and faces to make a sheet with a honeycomb larger, and the oxygen atoms are in one of the net || (100). The TeX6 octahedra are bound to this triangular faces shared by an octahedral and a sheet to make a compound layer, with H2O tetrahedral interstice of the ccp array. While the molecules in the interlayer gaps. The layers are TeO 6 octahedron itself is little changed (Te–O= held together only by hydrogen bonds. 1.95 Å), Tl is very irregularly coordinated by six Na[TeO(OH)5](#441) is very different from the oxygen neighbours at 2.11, 2.46, 2.86, 3.60, 3.88 above structures. It has a 2 × 2 × 2 cubic super- and 3.90 Å. There is a remarkable relationship 1+ structure of the ReO3 type with alternation of Na+ between the structure of Tl6 [TeO6] and that of 6+ 3+ and Te in octahedral coordination and no [Tl6 (TeO6)O6](#616, below), which can be

490 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

6+ FIG. 35. Examples of structures with monomeric Te O4–6 anions that are not part of a larger structural unit (Table 20, deposited). Small spheres: O (dark pink) when not part of a polyhedron. Large spheres: Cs (deep blue), K (purple), Li (pale blue), Na (dark yellow), Pb (grey), Rb (red) and Sc (pale yellow). Polyhedra: Te (dark green).

derived from it by stuffing with additional oxygen unprotonated oxygen atoms (O1) are ordered in a atoms (Fig. 35). Li4Zn[TeO6](#446) also has a cis fashion, and their orientation defines the polarity defect rocksalt superstructure, but this time, there of the structure along the z direction. The Te are no vacancies. Edge vectors of a face-centred octahedra are linked by Ag+ ions in irregular pseudocube are [½0½], ¯ [½⅓½] and [½⅓ ¯ ½] of the tetrahedral coordination (Ag–O = 2.23–2.58 Å). true monoclinic cell. and Zn are partially and the hydroxide oxygen O2 form massicot- ordered on three types of octahedral site, although like chains (cf. Hill, 1985) which lie in layers Li is dominant in all cases. || (400) between the Te octahedra, and run || [011] or  Ag2[TeO2(OH)4](#447)hasTeX6 octahedra [011] in alternate layers. Pb5[TeO6]O2 (#448) has arranged on the D lattice complex (Fischer and an unusual, very dense arrangement of Pb and Te Koch, 2006) of its Fdd2 space group. The atoms. Cations lie in rods || x that are in a

491 A. G. CHRISTY ET AL. pseudohexagonal array (√3b = 1.95 ≈ 2), but the x non-Te cations as part of a larger structural unit. The c coordinates are such that the cation substructure is first of these compounds is unusual, in that the not conventionally close-packed. Layers of cations || structural unit is in part organic: it is tris(tetramethyl- – (040) form nets in which cations form squares and disilyl) tellurate, [(CH3)2Si Si(CH3)2]3(TeO6) triangles, such that the connectivity is 36,3342,3342 (#457). The three tetramethyldisilyl groups each and then repeats along the z direction (Fig. 35). The bond to two oxygens of the tellurate octahedron, to arrangement can be generated from thinned and form a propellor-shaped neutral molecule. The faulted 2 × 3 blocks of hexagonal close-packing. monoclinic cell contains four such molecules, two Each cation has from 11 to 13 cation next-nearest of opposite rotational senses with their local pseudo- – triad axes pointing || ±[011], and two with their neighbours at 3.6 4.6 Å, while the oxygen coord-  ination number of Pb2+ is 5–8. Oxygen atoms are in pseudotriad axes || ±[011] (Fig. 36). interstices such that layers || (040) of tetrahedrally Compounds #458–461 have stoichiometry of 3+ coordinated oxygen alternate with layers where CN the form Na5[M (TeO4(OH)2)2] · 16H2O, where M = Cu, Ag and Au, except that #459 is a variant of =5–6. Pb6Cd[TeO6]O4 (#449) has an approximately + + ccp array of Pb, Cd and Te atoms, the unit cell #458 with 13% of the Na replaced by H . All are containing a 2 × 2 × 2 array of distorted face-centred isostructural. Two TeX6 octahedra share trans edges of a MO square in these compounds, the square- cubes, with irregular PbO4–6 polyhedra, CdO6 4 planar coordination being typical for M3+ in a low- trigonal prisms and TeO6 octahedra. 3+ spin d8 electronic configuration. The hydrogen The compounds A2 [TeO6](A =Y,LaandGd; atoms were located in the refinement of #461, #450–452) have the enantiomorphic (P212121) where they are located on the Te ligands that lie out structure of the orthorhombic form of Nd2WO6 of the principal plane of the cluster. The corre- (Efremov et al., 1984). The TeA2 substructure is in sponding Te‒O distances are long, 1.98–1.99 Å, the cotunnite (PbCl2) arrangement (Léger et al., 1996, and cf. #432 above), with oxygen atoms compared to 1.97 Å for the Au=Te bridging coordinated by Te + 2A or Te + 3A so as to form two oxygens and 1.85–1.86 Å for the unprotonated non-bridging Te ligands opposite the Te=M shared different types of AO7 polyhedron. Conversely, 3+ 3+ edge. The lath-shaped [Te=M=Te] clusters all have A2 [TeO6]withA =Sc, Yb, In or Tl adopt a different, trigonal structure (#453–456). These their long axes || [111] of the triclinic cell, and their – principal plane approximately || (211). These compounds have either smaller A O bonded  distances than those above or A cations with structural units cross-link layers || (101) of NaX6 relatively large non-bonded radii in the sense of polyhedra, which contain the additional H2O O’Keeffe and Hyde (1981), so all oxygen atoms are molecules (Fig. 36). 3-coordinate. The structure adopted is shared with The next three compounds #462–464 feature similar trimeric [Te=M=Te] heteropoly clusters malladrite, Na2[SiF6] (Babel, 1967). The oxygen atoms are approximately hcp, with (A, Te) cations containing a high-valence noble metal cation, but 4 5 the central polyhedron is an MX octahedron rather filling variously /9 or /9 of the octahedral 6 interstices between alternate oxygen layers, and than an MX4 square. The three structures are all 4+ the smaller minority cation (Te ≡ Si) forming a different. K6Na2[Pt (OH)2(TeO5OH)2] · 12H2O (#462) has all [Te=Pt=Te] clusters parallel, with substructure with the AlB2 arrangement (Hofmann  and Jäniche, 1935). Every occupied cation site long axes || [101] and equatorial planes of octahedra alternates with vacancies along z, so as to avoid || (101). The clusters are held together through + – face-sharing of octahedra (Fig. 35). Note that #453– separate Na(H2O)6 octahedra and K ions in 6 8 3+ 6+ 456 could be considered as examples of [A (TeO )] coordination. In Rb2Na4[Os O2(TeO4(OH)2)2]· 2 6 #463 frameworks, given the relatively low CN and high 16H2O( ), the [Te=Os=Te] complexes have bond valence for the A cations, but they are included their long axes || [010] and equatorial planes || 2– here because of the chemical similarity to #450–452 (102). They share the two O ligands of one and the isostructurality with malladrite, in which the Te (Te2) with similarly oriented edge-sharing + A cation Na is much more weakly bound. tetramers of NaX6 octahedra, Na4O2(H2O)16,to form long structural rods || y, which are held together by 8-coordinated Rb+. Despite the similar 6+ 6+ Monomeric Te X6 as part of a larger structural stoichiometry, Na6[Ru O2(TeO4(OH)2)2] · 16H2O unit that is a finite cluster (#464) has a very different triclinic structure with Table 21 (deposited) lists compounds #457–502,in trimer long axes || [223] and equatorial planes || which monomeric TeX6 anions are strongly bound to (302). These structural units act as bridges between

492 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

6+ FIG. 36. Examples of structures with monomeric Te O4–6 anions that are part of a larger structural cluster (Table 21, deposited). Small spheres: C (black), H (pale pink) and O (dark pink) when not part of a polyhedron. Medium spheres: Mn (magenta) and Si (blue). Large spheres: Ce (pale yellow), K (purple), Na (dark yellow) and Rb (red). Polyhedra: Au (yellow-brown), Mo (dark grey), Pd (pale grey) and Te (dark green).

layers || (100) in which NaX6 octahedra share octahedra share the remaining Pd ligands to form 3- corners, edges and faces with each other. The H rings with both Pd atoms, and in addition make a atoms were located in this refinement, and are again third bond to the oxygen atoms of the Pd = Pd edge. confirmed to be located on the oxygen atoms away The hydroxide H atoms are not located in the from the principal plane of the cluster (Te–O= structure. They are most probably located on the 1.98–2.01 Å), rather than the terminal oxygen non-bridging oxygen atoms of TeX6 (of which there ligands in that plane (Te–O = 1.85–1.86 Å). are 14 per cluster), but only two of these have long 4+ K2Na8[Pd2 Te 4O18(OH)6] · 20H2O(#465) has a Te‒O distances (Te1–O4 = 1.99 Å) as opposed to heteropoly hexameric cluster with a central core of the typical 1.80–1.83 Å. The rhombus-shaped two edge-sharing PdX6 octahedra. Each shares its clusters have long axes || [011] and are flattened || trans edge with a Te1 cation, while the two Te2 (111). They lie in layers parallel to that plane with

493 A. G. CHRISTY ET AL.

NaX octahedra, while additional NaX and KX lie (H O) ) [Mo TeO ]·6H O(#479), || (611) in (Nd 6 6 7 2 6 2 6 24 2  between the layers (Fig. 36). (H2O)7)2[Mo6TeO 24]·5H2O(#480) and || (411) in A large group of structures feature the (Nd(H2O)7)2[Mo6TeO 24]·5H2O(#481), although 6+ 6+ 6–  [M6 Te O24] Anderson–Evans heteropolyanion, they are strongly canted || (201) in the Pr analogue where M = (Mo or W), and six MO6 octahedra form a of the latter compound (#478). In K6(Eu hexagonal ring around a central TeO6 octahedron (H2O)7)2[Mo6TeO24]2 ·16H2O(#488), layers of (Anderson, 1937; Evans, 1948, 1974). The shape two differently oriented and symmetrically inde- and size of the unit cell is controlled largely by the pendent Mo-Te hexagons alternate along the z axis; stacking of these large, tabular structural units, which one type has EuO2(H2O)7 polyhedra connecting are held together principally by hydrogen bonds to them into columns || y, while the other type does not. + + hydrated alkali cations or NH4 (#466–470), hydrated AmatrixofCN9–10 hydrated K ions holds the lanthanide cations (#471–487)orboth(#488–490), layers together. The Gd analogue (#489) is nearly hydrated transition elements (#491–497)oralkalis isostructural, but is in a different axial setting, with plus additional molecular Te(OH)6 (#498–502). the layers of hexagons || (010) not (001), and the Although the alkali tellurohexamolybdates and Gd‒Mo‒Te columns || x,noty. Also, slight atomic tungstates are all triclinic with very similar cell rearrangements lead to doubling of the c parameter dimensions, they differ in detail. Li6[Mo6TeO 24]· relative to the corresponding a parameter of #488. 18H O(#466) has the planes of the Mo–Te (Co(H O) ) [Mo TeO ] and its Ni analogue 2  2 6 3 6 24 hexagons || (233), with LiX6 octahedra between (#490–491) have a simple, highly symmetrical 6– them, sharing edges to form rods of rocksalt-like rhombohedral structure in which [Mo6TeO 24]  2+ structure || [011]. Na6[Mo6TeO 24] · 22H2O and its hexagons alternate with triangles of [M(H2O)6] W analogue (#467–468) have layers of NaX6 octahedra (M = Co or Ni) to make columns polyhedra || (110), between M‒Te hexagons that running along the threefold rotation axes. lie parallel to approximately (643). Rb [Mo (NH ) (M2+(H O) ) [Mo TeO ]·H O(M = Mn, 6  6 4 2 2 3 2 6 24 2 TeO 24] · 10H2O(#469) has hexagons || (111), Co, Ni, Cu and Zn; #492–496) (Fig. 36) and the sitting in voids in a three-dimensional framework Ni‒W analogue (#497) are also highly symmet-  of RbX7–9 polyhedra. (NH4)2Na4[Mo6TeO 24]· rical (cubic, space group Pa3, a ≈ 14 Å). The + 16H2O(#470) has layers || (001) of NH4 and TeM2 part of the structure forms a distorted Mo‒Te ions, alternating with layers of monomeric fluorite array of the type found as predicted for NaX6 octahedra and Na2X10 dimers. SiO2 at very high pressure by Park et al. (1988) (Ce(H2O)4)2[Mo6TeO 24]·3H2O and the Nd and found experimentally for SnO2 above 21 GPa analogue (#471–472)haveMo‒Te hexagons that by Haines and Léger (1997). Because of the lie in layers || (020), and are canted slightly relative distortion, M2+ bonds to only three of its four to that plane in opposite senses in alternate layers. nearest Mo‒Te hexagons, as well as to three water Layers are cross-linked by AX9 polyhedra (A =Ce molecules. The other components in the structure, + or Nd), while additional H2O molecules lie in the NH4 ions and the remaining H2O molecule (O6) Mo‒Te layers. The next several compounds are all form hydrogen-bonded dumbells (N…O = 2.84 Å) triclinic with similar unit-cell dimensions, with which, together with the Te atoms, are arranged 2– only a single orientation of Mo‒Te hexagon. Again, similarly to the covalent [S2] dumbells and Fe in these lie in layers with some of the water molecules, , FeS2. while AXn polyhedra lie between the layers and The remaining compounds of this section are bridge them. The coordination number, n, is usually alkali tellurohexamolybdates which also contain 3+ 9, although it is reduced to 8 for the smaller Eu , Te(OH)6 molecules as adducts. Li6[Mo6TeO 24] 3+ 3+ Ho and Yb cations in #485–487. The layers (H2O)18 · [Te(OH)6](#498) has sinuous chains of are usually || (100), although they are || (110) for LiX4–6 polyhedra and Te(OH)6 || y, which cross-link (Sm(H2O)5)2[Mo6TeO 24]·6H2O(#482), which has Mo‒Te hexagons that are oriented || (103). a different axial setting. The orientation of the Mo‒Te Cs6[Mo6TeO 24](H2O)2 · [Te(OH)6]2 (#499) has hexagons varies depending on the hydration state one Mo‒Te anion per unit cell oriented || (112), and cation size. For (La(H O) ) [Mo TeO ]· embedded in a trellis-like open framework of CsX – 2 7 2  6 24 7 10 6H2O(#473), the hexagons are || (101), while for and Te(OH)6 polyhedra. Rb6[Mo6TeO 24](H2O)6 · the less hydrated (La(H2O)6)2[Mo6TeO 24]·6H2O [Te(OH)6]2 (#500) has a C-centred monoclinic cell (#474) and its Ce analogue (#475), they lie flatter, with strong 1c pseudosymmetry, and thus four Mo‒ 2 approximately || (411) (Fig. 36). The hexagons also Te hexagons per cell. These are all oriented || (010) lie flatter for the Nd compounds: || (411) in (Nd and alternate with Te(OH)6 molecules along the y

494 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

6+ FIG. 37. Examples of structures with monomeric Te O6 anions that are part of a larger structural chain or layer (Table 22, deposited). Small spheres: H (pale pink) and O (dark pink), when not part of a polyhedron. Large spheres: K (purple) and Pb or Tl (grey). Polyhedra: Cu (cyan), Mg (pale blue) and Te (dark green). Additional long Cu–O bonds complete octahedra in frankhawthorneite (#512) and link layers into a framework.

2+ direction, forming Te-rich rods in a matrix of RbX7–9 Table 22 (deposited). [Hg (TeO2(OH)4)] (#503) polyhedra (Fig. 36). The ordered K‒NH4 compound has TeX6 octahedra linked via their cis unprotonated #501 is nearly isostructural, as is the more highly ligands through linear 2-coordinated Hg2+ into hydrated NH4 compound #502 (although this is in chains || y, which pack in a hexagonal array. Chains an A-centred axial setting). are connected only through hydrogen bonds and long, weak Hg…O bonds (within-chain Hg–O 6+ – Monomeric Te X6 as part of a larger structural distances are 2.02 2.05 Å, while the two next unit that is an infinite chain nearest oxygen atoms to Hg are at 2.67 and 2.75 Å). 2+ The next few structures have TeX6 anions that are In [(Hg2 )(TeO2(OH)4)] · [Te(OH)6]·2H2O strongly bound with other cations into one- (#504), TeX6 octahedra linked through trans dimensional structural units. They are listed in unprotonated ligands to linear [Hg–Hg]2+ dimers,

495 A. G. CHRISTY ET AL.

5+ forming infinite chains || [101]. These lie in layers || (NH4)2V2 TeO 8(OH)2 ≡ (NH4)2[(VO2)2(TeO4(OH)2)] (010), which alternate with layers containing Te (#509) has TeX6 octahedra sharing non-opposed (OH)6 and H2O molecules. is even more edges with edge-sharing dimers V2O8 of VO5 strongly 2-coordinate than in the previous com- square pyramids. One of the bridging oxygens links pound, with one O neighbour at 2.11 Å, one Hg at to 1 Te + 1 V,while the other connects to 1 Te + 2 V 2.50 Å. and the next O neighbours not until 2.91 atoms. Small atomic displacements break the and 2.93 Å. K2[Cu(TeO4(OH)2)] · H2O(#505) has potential 2/a symmetry of the chain, so that there TeX6 octahedra sharing opposite edges with CuO4 are two distinct Te atoms and four distinct V atoms squares to form straight chains, which lie in layers || per repeat unit. These chains run || x and lie in layers + (002). Chains of alternate layers run || to [110] or to || (002), with NH4 ions between the layers. [110]. Water molecules and CN8–9K+ ions lie between the layers (Fig. 37). has no 6+ additional ligands within 3 Å. Very slight tilts and Monomeric Te X6 as part of a larger structural displacements reduce the symmetry from ortho- unit that is an infinite layer rhombic and centrosymmetric (space group Cccm) Table 22 also includes structures #510–547,where to monoclinic and acentric (Cc). The mineral monomeric TeX6 octahedra are linked with non-Te raisaite, (Mg(H2O)6)[Cu(TeO4(OH)2)] (#506) has cations to form two-dimensional strucural units. TeX6 octahedra sharing edges which are not Na2[Cu2(TeO6)] (#510)hasaCu‒Te layer || (001) opposite with CuO4 squares (Cu‒O = 1.94–1.98 that can be regarded as an ordered version of a Å), to form zigzag chains || z. These form a centred- brucite-like trioctahedral sheet, but with strong Jahn- 2+ rectangular array, which have [Mg(H2O)6] octa- Teller distortion of the CuO6 octahedra, giving Cu a hedra lying betwen them. The structure is held square of four O neighbours at 1.98–2.00 Å and two together through hydrogen bonds, and also weak more distant ligands at 2.53 Å. If all six neighbours Cu…O bonds: Cu has two O atoms of water are considered, then the structural unit has the same molecules at 2.78 Å, completing an elongated bond topology as those of #538–541 below. octahedron of ligands (Fig. 37). Ag4[Cu(TeO6)] However, unlike those structures, the oxygen atoms (#507) has TeO6 octahedra sharing an edge with one of #510 are approximately ccp in three dimensions, CuO4 square and corners with two others to make a and Na atoms are ordered in ⅔ of the octahedral sites 2– double chain running || z that zigzags in the (100) between [Cu2(TeO6)] layers. The structure can be plane. The double chain consists of Cu=Te‒Cu=Te regarded as an ordered defect derivative of the 1+ 2+ 4-rings, united by the shared edges. Two additional rocksalt type. NaTl3 [Cu4 (TeO6)2](#511)has O ligands are much closer to Cu than in #506 above similarly distorted Cu‒Te layers || (200), alternating (Cu–O = 2 × 1.98, 2 × 2.00 and 2 × 2.49 Å). If these with layers that contain an ordered array of Na+ in + are included to complete a CuO4+2 octahedron, the octahedral coordination and Tl in very irregular chains become ribbons of edge-sharing Cu and Te 6-fold coordination. The three-dimensional arrange- octahedra in which Cu atoms form a central zigzag ment of oxygen atoms can again be considered a backbone while Te sit on the outside of the ribbon. derivative of cubic close-packing, except that the The chains form a centred-rectangular array, and are coordination requirements of Tl cause the Cu‒Te‒O held together by three types of Ag+ ions in distorted layers to undulate, and lead to the Tl atoms being far octahedral coordination (Ag–O = 2.27–2.83 Å). from the centres of octahedral interstices. The oxygen atoms approximate ccp, with pseudo- Frankhawthorneite, [Cu2(TeO4(OH)2)], (#512), cube edge vectors || [¼0¾], [¯¼⅓¼] and [¯¼¯⅓¼]. If has oxygen atoms forming a slightly distorted hcp the structure is considered as a packing of (Ag, Cu, array, with close-packed layers || (002). Copper and Te) octahedra, then it is a superstructure of the Te atoms occupy octahedral interstices to form rocksalt type. Tl4[Cu(TeO6)] (#508) has Cu‒Te ribbons in which one Te atom alternates with two chains with the same topology as those of #507 and Cu along the y direction. Ribbons form a centred also forming an approximately centred-rectangular rectangular array, and share corners with their array, but this time running || x and zigzagging in the neighbours. However, Jahn-Teller distortion of the (011) plane of the triclinic cell. The oxygens do not Cu coordination polyhedron is of a similar degree form a continuous close-packed array as in #507, to that in #507–508 above (Cu–O = 4 × 1.98–2.06 Å but discrete close-packed ribbons which surround and 2 × 2.46–2.52 Å), so only the four shortest large channels || x. Four types of Tl+ ions in irregular bonds are counted when defining the structural 5–7 coordination hold the chains together, with their unit, which is hence not a framework but a layer || lone pairs pointing into the channels (Fig. 37). (101). In frankhawthorneite, the component

496 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS ribbons of the layer have each Te octahedron Cu2 at 2.00 Å and an unusually long distance of sharing two opposite edges with CuO4 squares, and 2.03 Å to Te, and is where the H is located. Between ribbons are linked through CN3 oxygen atoms in a Cu‒Te double layers are Pb atoms which show stepped pattern. The Jahn-Teller distortion also some positional disorder, and SO4 tetrahedra. Cu1 reduces the symmetry to monoclinic P21/n from has a square of O atoms at 1.91–2.00 Å and one at orthorhombic Pmnn, and allows ordering of the H 2.41 Å within the Cu‒Te layer, and a sulfate oxygen atom on O2, as shown by long Te–O bonds (1.99 atom at 2.46 Å. A differently oriented oblique slice rather than 1.91–1.92 Å). Layers are held together through an hcp anion array is an element of the by long Cu…O bonds and hydrogen bonds ‘tri-harmunite’ structure of #598, below. (Fig. 37). A similar arrangement of more regular The polytypes of (-3T and -4O), octahedra is found in kotoite, Mg3(BO3)2, which Pb[Cu3(OH)2(TeO6)] (#516–517) share a more has similar unit-cell dimensions but the ortho- complex layer type, in which rows of edge- rhombic space group, and has additional B atoms in sharing CuO4 squares =Cu1=Cu2= alternate with triangular coordination, providing strong links rows of CuO4 squares and TeO6 octahedra, between ribbons (Berger, 1988). The octahedral =Cu3=Te=. The coordination octahedron of the arrangement in the average structure of one form of Te is completed by sharing bridging oxygen atoms (H,Li)2[Ti(TeO6)] is also very similar (#585, of the all-Cu chain, thus making a layer containing below). Paratimroseite, Pb[Cu2(TeO6)] · H2O 5-rings [–Te=Cu3=Te–Cu1=Cu2–]. In projection (#513) has stepped layers || (002) composed by normal to the layer, the cations form a condensation of ribbons || x, in exactly the same hexagonal net, but the all-Cu chain is at a different topology as frankhawthorneite (#512), but the height from the Cu‒Te chain, so the layer has an layers are separated widely and also alternate overall polarity (Fig. 37). In the 3T polytype between two orientations related by a screw diad (originally known as ‘parakhinite’), the subchains axis, so their anions form disconnected oblique of layers point along x, y or –[110], successive slices of hcp structure rather than constituting a layers rotating by 120°, consistent with a screw three-dimensionally continuous close-packed sub- triad axis. There are three layers || (003) per P32/P31 structure. Water molecules and Pb2+ cations in unit cell. In the 4O polytype, layers are || (004), irregular 9-coordination lie between the layers, and alternate layers have subchains || [110] or [110], the Pb coordination geometry causes shift of the and the layers are related by the d glides of layers in the x direction such that any reflection the space group Fdd2. Note that a4O ≈ a3T, and symmetries are eliminated, and the space group is that a pseudohexagonal metric is retained, as 2+ P212121 rather than the Pbca or Pbcm of hypo- b4O ≈√3a4O. In both cases, Pb lies between thetical aristotypes. An elongated coordination the layers, in 8-fold coordination. Agaite, Pb3[Cu octahedron around Cu is completed by an interlayer (TeO5OH)](CO3)(OH) (#518) has layers || (020) water molecule at 2.42 Å and an additional tellurate in which alternating TeX6 and CuX5 polyhedra oxygen atom at 2.54 Å (Fig. 37). The structure of form a 63 honeycomb net. These polyhedra share timroseite is closely related (#555, below). non-opposing edges to form zigzag chains Sr2[Cu2(TeO6)]Br2 (#514) has edge-sharing trending || x, which are joined in the z direction ribbons of CuO4+1 square pyramids (Cu–O=4× by sharing of a fifth corner. Between the Cu‒Te 2+ 1.93–2.02 Å and 1 × 2.36 Å) and TeO6 octahedra layers lie triple layers of CN8 Pb ions, running || y, which share corners with each other so additional OH– ions (bound to 3 Pb) and a 2– as to form a continuous layer || (100) in which the central plane of CO3 ions (each oxygen atom oxygen atoms again form the stepped, hcp slice of bound to 3 Pb as well as to C). The orientation of #512–513. Interlayer SrO4Br3 polyhedra hold the Cu=Te zigzags in the structural unit and the – structure together. The Br anion is also a very pointing direction of CO3 triangles both define a distant sixth ligand for Cu2+ (2.97 Å). In bairdite, polarity in the z direction (Fig. 38). 4+ 6+ Pb2[Cu4(TeO5OH)2](SO4)·H2O(#515), two Na1.8[(Sn0.9Te 0.1)(TeO6)] and Na2[Ge(TeO6)] stepped Cu‒Te layers || (100) stack adjacent to (#519–520) both have a trigonal structure in each other, related by a screw diad axis, and are which oxygen atoms approximate hcp (cf. #512). … linked through long Cu O bonds so as to form a It is a superstructure of one of the TlSbO3 polytypes double layer (Cu2–O4 = 2.36 Å, as opposed to (Bouchama and Tournoux, 1975). The other such 2+ 4+ 1.94–2.04 Å for the four shortest Cu2–O bonds, polytype has the structure of ilmenite (Fe Ti O3) and 2.57 Å for an additional within-layer distance in that ⅔ of the octahedral interstices between each that completes the octahedron). O4 also has another pair of oxygen layers are occupied by cations, and

497 A. G. CHRISTY ET AL.

6+ FIG. 38. Examples of structures with monomeric Te O6 anions that are part of a larger structural layer (Table 20, deposited). Small spheres: H (pale pink) and O (dark pink) when not part of a polyhedron. Large spheres: Cl (green- #518 yellow) and Pb (grey). Black triangles in :CO3 groups. Polyhedra: Al (pale grey), Cu (cyan), Te (dark green) and U (yellow).

6+ that two types of cation occupy alternate cation Te ), where M = (Sn or Ge). NaO6 octahedra share layers. However, whereas the vacant octahedral faces with TeO6 octahedra above and below along 4+ sites in the ilmenite polytype are offset in a the z direction, while M O6 octahedra have vacant sequence ABCABC so as to produce a 6-layer sites above and below. Note that such face-sharing rhombohedral cell (space group R3), the vacant relationships would not be achievable in an sites in the current structures are arranged in a ilmenite-like polytype, where every occupied pattern ABAC, giving a 4-layer trigonal cell with octahedron shares one face with another that is  space group P31c. In these tellurate compounds, occupied. Sr[Ge(TeO6)] (#521) also has hcp layers of Na cations alternate with layers of (M4+ + oxygen atoms, and a primitive trigonal cell that

498 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS has the same ∼5Åa parameter but half the c analogue of these compounds was discussed above parameter of #519–520. (Ge+Te) atoms occupy (#510). ⅔ of the octahedral sites every other octahedral Leisingite, (Mg(H2O)6)[Cu2(TeO6)] (#541) has 2– cation layer, forming a honeycomb pattern with Ge a layered [Cu2(TeO6)] structural unit || (001) and Te alternating, while Sr atoms are in the which resembles the trioctahedral layers of #538– intervening layers, above and below the vacant sites 540, with no evident Jahn-Teller distortion of in the (Ge+Te layer). This is the P312 structure of CuO6 octahedra (Cu–O = 6 × 2.11 Å), unlike the NaNi4+I7+O (Brown, 1969), which is a cation- layers of #510–511. Isolated [Mg(H O) ]2+ octa- 6  2 6 ordered superstructure of the P31m type of Li2ZrF6 hedra lie between these layers, and connect them 2+ 5+ (Brunton, 1973) or rosiaite, Pb Sb2 O6 (Basso through hydrogen bonding. Apart from a 3+ 3+ 6+ et al., 1996). The compounds A [Cr (Te O6)] 30° rotation of the Mg octahedron and the (A = La, Pr, Nd, Sm–Yb and Y; #522–534) and locations of H atoms, this mineral is isotypical La[Fe(TeO6)] (#535) have a polytypical relative of with zincalstibite (Bonaccorsi etal., 2007), a the Sr[Ge(TeO6)] structure in which the c repeat is member of the cualstibite group of the hydrotalcite doubled from 5.4 Å to ∼10 Å and the space group supergroup of Mills et al. (2012). The corres-  changes to P3,because the relative positions of (Cr, pondence can be shown as [Cu2(TeO6)][Mg Fe) and Te are reversed in alternate Cr‒Fe‒Te (H2O)6] (leisingite) ≡ [Zn2Al(OH)6][Sb(OH)6] layers. This structure is also that of colquiriite, CaLi (zincalstibite). Zincalstibite has a lower-symmetry   [AlF6] (Yin and Keszler, 1992). Compound #535 space group (P3 as opposed to P31 m), but very shows some Fe‒Te disorder which may imply similar unit-cell parameters a = 5.321(1) Å and short-range mixing of the two cations, but given the c = 9.786(2) Å (Fig. 38). large difference in charge, more probably implies Mojaveite, [Cu6(TeO4(OH)2)(OH)7]Cl (#542), 1 displacement of layers by stacking faults, while has brucite-like octahedral sheets in which /7 of 6 1 retaining two-dimensional order within layers. the cations are Te and /7 are Cu, while /14 of the Thus, it may have a nanoscale intergrowth of anions are Cl, and thus are not counted as part of the rosiaite and colquiriite structure types. structural unit. The degree of Jahn-Teller distortion Ba[Ge(TeO6)] (#536), despite the chemical is relatively small, half the Cu are regarded as similarity to its Sr analogue #521, has a different coordinated by five (O,OH) ligands (+1 Cl) while structure with the same P312 space group. Oxygen the other half have six O neighbours. The ordering atoms are double-hexagonal close-packed (AABB pattern of cations and anions forces the structure to stacking), and layers of (Ge+Te) in octahedral adopt the relative low-symmetry polar space group coordination alternate with layers of BaO6 trigonal R3. The layers are held together by hydrogen bonds prisms. Backite, Pb2[Al(TeO6)]Cl (#537) has (Fig. 38). The mineral is isostructural with 5+ dioctahedral AlTeO6 layers resembling the MTeO 6 bluebellite, Cu6[I O3(OH)3](OH)7Cl, which is unit in structures #519–536 (Fig. 38). However, unusual in that Te6+ does not have a lone pair of these layers are now widely spaced, and the oxygen electrons while I5+ does so (Mills et al., 2014a). atoms are not three-dimensionally close-packed. The substitution is presumably facilitated by the Instead, the unit cell contains one such layer, polar symmetry of the Te/I site, which frees the separated from the next by layers of Pb, Cl and Pb coordination environment to distort. Fuettererite, such that each Pb atom lies above a vacant Pb3Cu6(TeO6)(OH)7Cl5 ≡ (Pb3(OH)Cl3)2[Cu6(Te octahedral site of the Al‒Te layer and is coordinated O6)(OH)6]2Cl4 (#543), has Cu‒Te layers very by 3O + 6Cl. The compounds Na2–x[M2(TeO6)] similar to those of mojaveite, although all Cu (M = Ni, Zn and Co, x =0–0.05; #538–540)are atoms now have one Cl as a sixth ligand, rather than based upon a AABB stacking of oxygen atoms, like just half of them. There are Cl atoms on both sides #536. M and Te cations are in octahedral coordin- of the layer, and the structure retains a centre of ation, and form a structural unit that is an ordered inversion symmetry. Pairs of Cu‒Te‒O layers brucite-like trioctahedral layer, with Na cations are linked through a shared Cl atom, and these partially occupying the trigonal prismatic sites layers are stacked with the other components + between the M‒Te layers. The Na ions are highly between them in the sequence [Cu6(TeO6) … … … … mobile, leading to fast-ion conduction in these (OH)6] Cl [Cu6(TeO6)(OH)6] Cl (Pb3(OH) … … … compounds (Evstigneeva et al., 2011). Small Cl3) Cl (Pb3(OH)Cl3) Cl (Fig. 38). atomic displacements result in the Zn and Co Markcooperite and its synthetic analogue, 2+ 6+ compounds being acentric (P6322), while the Ni ideally Pb2 [(U O2)(TeO6)], have a quite different compound has space group P63/mcm. The Cu type of layer (#544–545). TeO6 and UO6 octahedra

499 A. G. CHRISTY ET AL.

6+ FIG. 39. Examples of structures with monomeric Te O6 anions that are part of a larger structural layer or framework (Tables 22–23, deposited). Large spheres: Ba (yellow-green), Ca (orange), Hg (pale grey) and Pb (dark grey). Polyhedra: As (brown-green), Be (pale blue), Cu (cyan), Nb (grey octahedra), Te (dark green) and Zn (grey tetrahedra). In #548, the two Hg–O bonds per Hg atoms are omitted for clarity.

both share four corners to form a layer with 4-rings, with the presence of linear [O = U = O]2+ similar to that of Fig. 14c but with alternation of Te groups (Fig. 38). The natural mineral shows 25% and U atoms. These layers lie || (100) and have CN7 substitution of Te on the U site, but the pattern Pb2+ ions between them. In the end-member synthetic of bond-length variation remains similar. The compound (#545), the Te octahedron is relatively substitution makes the structure transitional regular (Te–O = 2 × 1.91, 2 × 1.94 and 2 × 1.95 Å) towards those with continuous layers of corner- while the U octahedron is strongly compressed sharing TeO6 octahedra (Fig. 14c), such as #688– (U–O = 2 × 1.84, 2 × 2.24 and 2 × 2.29 Å), consistent 670 below.

500 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

ThV5+TeO ·2H O ≡ Th[(VO ) (TeO )] · 2H O (Geller, 1967; O’Keeffe and Hyde, 1985). The 2 10 2 2 2 6 2  (#546) has layers || (200) consisting of TeO6 Ia3d cubic cell of typical garnets A3B2C3X12 has a octahedra, VO5 (V1) trigonal bipyranids and VO4 2 × 2 × 2 array of body-centred cubes of B atoms tetrahedra (V2). V1 polyhedra share an edge with corresponding to Si of Cr3Si, and non-intersecting Te on one side and a corner with Te on the other side rods || <100> directions of alternating A and C in the z direction, while V2 tetrahedra share a corner atoms corresponding to Cr. Anions X occupy with Te on each side in the y direction, so the layer distorted tetrahedral interstices, so that each anion has square-shaped 8-rings of alternating Te and V in is bonded to 2A + B + C, while coordination which Te is 4-connected while V is always only 2- numbers of A, B and C are, respectively, 8, 6 and connected. Each V atom has two non-bridging 4. The numerous mineralogical examples of garnets ligands with short V–O distances (1.63–1.67 as werereviewedbyGrewet al. (2013). The B2C3X12 opposed to 1.77–2.04 Å), validating their descrip- substructure forms a framework in which each X + 4+ tion as vanadyl groups [VO2] .Th ions are in links to one cation of each type. Depending on the 9-coordination between the layers. Ba2Nb2TeO 10 ≡ relative bond valences, it may be reasonable to Ba2[Nb2O4(TeO6)] (#547) has corrugated layers identify within this framework either BX6 or CX4 as || (020) containing zweier chains of corner-sharing a principal anionic complex. An example of the NbO6 octahedra which run || x. The TeO6 former would be cryolithionite, Na3Al2Li3F12 ≡ octahedron shares one edge and one corner with a Na3Al2[LiF4]3 more appropriately than pair of Nb octahedra in the chain on one side, Na3Li3[AlF6]2, while silicate garnets are examples making an [‒Nb‒Te=Nb‒] 3-ring, and the same where the strongest-bound cation is in the tetra- with the next chain on the other side, so that the hedron: grossular, Ca3Al2Si3O12 =Ca3Al2[SiO4]3. layer has 3- and 6-rings with the topology of the Several tellurate garnets are known, in which the kagome net. Ba2+ ions between the layers are B cation is Te6+; these compounds are of the first 9-coordinated. Although the layer contains four type, because of the high Te–O bond valence. non-tellurate oxygen atoms per formula unit, only These include the mineral yafsoanite (Fig. 39), 3+ two of these are non-bridging oxygen atoms with Ca3[Zn3(TeO6)2](#549) and also synthetic Na3[M3 short Nb–O distances (1.78 Å; compare 1.90–2.26 Å (TeO6)2](M =Fe0.5Al0.5 or Ga, #550–551). for all other Nb–O) (Fig. 39). Nd3Li3.05 [(Te0.975Sb0.025)O6]2 (#552) and Nd3Li4[(Te0.5 Sb0.5)O6]2 (#553) are included here 6+ Monomeric Te X6 as part of a larger structural because they still have the garnet structure, albeit unit that is a framework slightly modified. However, the C cation Li is now A large group of compounds have TeX6 octahedra so low in charge that it no longer forms a structural strongly bound to non-Te cations to form a unit with the octahedral cations: the Nd–Obond three-dimensional framework. These are listed as valence (0.375) is larger than that of Li–O (0.25). 2+ #548–618 in Table 23 (deposited). [Hg3 (TeO6)] Furthermore, both these compounds have consid- (#548) has a highly symmetrical structure with a erably higher Li contents than the 2 atoms per large cubic unit cell (Ia3, a ≈ 13 Å). Two types of formula unit expected for a normal garnet, due to Te atom are arranged as a 2 × 2 × 2 block of CsCl stuffing of additional Li into normally vacant unit cubes, while the Hg atoms are positioned so as interstices, and the Li are very mobile in the to form, in combination with Te, a slightly structure, making the compounds fast-ion conduc- perturbed 2 × 2 × 2 array of cubes with the Cr3Si tors (O’Callaghan et al., 2008). 5+ arrangement (Boren, 1933; Andersson, 1978), LaV3 TeO 12 ·3H2O ≡ La[(VO2)3(TeO6)] · 3H2O analogous to the cations of the garnet structure (#554) has a framework in which an approximately (O’Keeffe and Andersson, 1977; Grew et al., 2013; primitive cubic array of TeO6 octahedra are linked #549–553 below), which has the same space group to all six of their neighbours through 2-connected 2+ 3+ and similar unit-cell parameter. However, Hg has VO4 tetrahedra. La ions are near the centre of linear two-fold coordination, unlike the CN4/CN8 each cube. Thus, the LaTeV3 substructure corre- cations of garnet: two Hg‒O distances are 2.06 Å, sponds to the atomic arrangement of an ABX3 while the next neighbours are not until 2.57, 2.59, perovskite. The La atom is coordinated by six 2.76 and 2.83 Å. Links Te‒O‒Hg‒O‒Te connect oxygen atoms of the framework but also by three each Te atom to six out of the eight neighbouring Te water molecules which all lie on one side of La, of the other type (Fig. 39). reducing the symmetry to polar rhombohedral R3c. The important garnet structure is an ordered and Relative to a cubic metric, the structure is slightly anion-stuffed superstructure of the Cr3Si type stretched along the rhombohedral triad axis

501 A. G. CHRISTY ET AL.

(c/a = 2.48 = √6.15, rather than √6). As is typical Pb[Cu3O(TeO6)] (#558) has Cu‒Te‒O rods for vanadyl tellurates, V–O distances are much running || y in which the oxygen atoms approximate shorter (1.63–1.64 Å) for the V‒O‒La oxygens small blocks of cubic close-packed structure. than for the V‒O‒Te oxygens (1.80–1.84 Å). Relatively regular TeO6 octahedra alternate with The minerals of the dugganite group include pairs of Cu1 atoms in elongated CuO4+2 polyhedra, dugganite itself, Pb3[Zn3(TeO6)(AsO4)2](#555), while Cu2O4 squares brace the sides of the rods, as its phosphate analogue kuksite (#556) and also well as sharing corners with Te and Cu1 atoms of cheremnykhite (the vanadate analogue), neighbouring rods to form a framework with large 2+ Pb3[Zn3(TeO6)(VO4)2] (Kim et al., 1990), whose channels || y, which contain CN7 Pb ions. structure has not been refined, and joëlbruggerite, Jensenite, Cu3TeO 6 ·2H2O ≡ [Cu3(H2O)2(TeO6)] 5+  ideally Pb3[Zn3(Sb O6)(AsO3.5(OH)0.5)2] (Mills (#559), has brucite-like Cu2TeO 6 layers || (101) in et al., 2009c), which has only minor Te substituting which Cu and Te are ordered in a honeycomb for Sb. The dugganite structure has layers || (001) in pattern. While the Te octahedral are quite regular which 3-connected AsO4 on triad axes and (Te–O = 1.89–1.98 Å), the Cu polyhedra show the 2-connected ZnO4 tetrahedra share corners to usual Jahn-Teller distortion, with Cu–O = 4 × 1.94– form a net of trefoil-shaped 12-rings in which Zn 2.06 Å and 2 × 2.32–2.45 Å. The layers are bridged and As alternate. One third of the triad axes does into a framework by an additional Cu cation in the not have an As tetrahedron, but instead have Te interlayer gap that is in strict square-planar octahedra between two Zn‒As layers and linking coordination. This Cu atom (Cu1) has as ligands the layers. Each TeO6 octahedron links to three Zn two interlayer water molecules, plus a tellurate tetrahedra below and to three more above. Thus, the oxygen atom in each layer (Fig. 39). three-dimensional framework that results contains Timroseite, Pb2[Cu5(TeO6)2](OH)2 (#560) has [Zn‒Te‒Zn‒Te] 4-rings and [Zn‒As‒Zn‒Te‒Zn‒ stepped hcp layers || (002) of the type previously As] 6-rings (Fig. 39). seen in frankhawthorneite, paratimroseite, [Be4O(TeO6)] (#557) has a simple face-centred Sr2[Cu2(TeO6)]Br2 and bairdite (#512–515, cubic structure in which Be4O6 tetrahedra, with Be above). As in paratimroseite, the layers are in two atoms at the corners and O1 oxygen atoms along different orientations which alternate, but in the edges, and additional oxygen atoms (O2) are timroseite, they are connected into a three- arranged in the ‘zincblende’ arrangement. Thus, dimensional framework through additional CuO4 6– there is a rather open [Be4O7] framework in squares (Fig. 40). Large channels remain || x, which which O2 is at the centre of an anion-centred contain OH– anions and Pb2+ in 8–10 coordination. tetrahedron, where four BeO4 tetrahedra meet. All Cu are in square-planar coordination if a 7 Oxygen atoms occupy /8 of the positions of ccp, bonding cutoff of <2.27 Å is used, but all Cu with the eighth position vacant, and the sixth O1 atoms also have one channel OH– anion at 2.27– oxygen atom defines an octahedral interstice that 2.64 Å, and Cu1 and Cu2 within the hcp layers, also contains Te (Fig. 39). The structure may be have an additional tellurate oxygen at 2.47–2.71 Å. compared with that of swedenborgite, Na[Be4O , [Zn6Cu3(TeO6)2(OH)6] · (AgxPby 5+ (Sb O6)], which has a similar stoichiometry. In Clx+2y)(#561), has a more explicitly nanoporous swedenborgite (Huminicki and Hawthorne, 2001), structure in which hexagonal rings of six corner- 7 the oxygen atoms again occupy /8 of the positions sharing ZnO2(OH)2 tetrahedra alternate along z of ccp, but the stacking of close-packed layers is with layers || (001) in which TeO6 octahedra share now ABAC rather than ABC, and the eighth position edges with CuO4 squares to form a honeycomb net contains CN12 Na+ ions. There is also a unique with walls Te=Cu=Te surrounding large hexagonal octahedral interstice, which contains Sb, and a voids. The hexagonal channels contain rods of + 2+ – Be4O7 framework in which Be4O6 tetrahedra can be alternating, partially occupied (Ag ,Pb ) and Cl identified. However, the additional oxygen atom sites (Fig. 40). that connects the tetrahedra is no longer bonded to A large group of tellurate compounds have a four Be, but instead to two Be + Sb, while the superstructure of the perovskite type (#562–584). oxygen that centres an OBe tetrahedron is now part An aristotypical ABO perovskite has a unit cube 4 3  of the Be4O6 tetrahedron. Apart from #557 and with Z =1, a ≈ 4 Å and space group Pm3m. The swedenborgite, isolated OBe4 tetrahedra have also compounds described here all have two types of been reported from two polymorphs of (Be4O) octahedrally coordinated B atom, one of which is 6+ (NO3)6 (Haley et al., 1997; Troyanov et al., 2000; Te . Other perovskite variants have been described 2+ 4+ Krivovichev et al., 2013). earlier, including M Te O3 (M = Co, Ni and Cu)

502 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

6+ FIG. 40. Examples of structures with monomeric Te O6 anions that are part of a larger structural framework (Table 23, deposited). Large spheres: Ag (pale grey), Ba (yellow-green), Ca (orange), Li (pale blue) and Pb (dark grey). Polyhedra: Bi (violet), Co (magenta), Cu (cyan), Sn (pale blue), Te (dark green) and Zn (pale grey).

4+ 4+ with Te as the A cation (#140–142), Cs2[Te2 O5] in the absence of strong Jahn-Teller or other 4+ 1+ with Te as the B cation and some ordered oxygen distortion (as occurs in ‘CsAuCl3’ =Cs2[Au Cl2] 6+ 3+ vacancies (#195), the wickmanite-like Na[Te O [Au Cl4]; Tindemans-van Eijndhoven and (OH)5], with a vacant A site (#441), and the Verschoor, 1974). It is possible that the oxygen 6+ complex superstructures of M3[Te O6](M=Sr positions in this structure need reinvestigation. A 2+ and Ba; #442–443). One form of Pb2[Co (TeO6)] rhombohedral polymorph occurs at high and at low 2+ (#562) has Te alternating with Co in the B sites, a temperature (#582, below). A2[Cu (TeO6)] (A =Sr √2×√2 × 2 superstructure of the basic perovskite and Ba; #563–564) have similar cell dimensions to type, and tetragonal space group I4/mmm, consist- #562 but the tetragonal space group I4/m is ent with slight tetragonal distortion but no octahed- obtained by octahedra tilt according to the a0a0c– eral tilt. Howard et al. (2003), in their analysis of pattern in these compounds, independent of the possible octahedral tilt systems (Glazer, 1972) and Jahn-Teller distortion of the CuO4+2 octahedra symmetries of ordered , expressed (Howard et al., 2003; Howard and Carpenter, scepticism about the existence of such structures 2010). The ICSD gives as the archetype of this

503 A. G. CHRISTY ET AL. perovskite structure Sr2NiWO6 (Köhl, 1973). close-packed array, with X3A ordered in the Cu3Au Ba2[Cu(TeO6)] (#564) has another polymorph pattern. The structure can thus be described as an whose structural topology is polytypically related ABC stacking of AX3 layers, with B cations filling to that of normal perovskites (#587, below). the X6 octahedral interstices. Other ‘perovskite NaLa[Mg(TeO6)] (#565) has similar cell dimen- polytypes’ can be produced by stacking AX3 sions again but in addition to two types of B cation differently (Mitchell, 2002). These structures ordered in a ‘rocksalt’ fashion, there are two types require some BX6 octahedra to share faces, of A cation ordered layerwise along the z direction, implying short B…B distances and the possibility … and the symmetry is monoclinic, P21/m. However, that they may require some B B bonding inter- most of the perovskites with √2×√2 × 2 super- action to be stable. Most mineralogical perovskites structure have the P21/n space group exhibited by are derived from only the 3C polytype, although cryolite, Na3AlF6 =Na2[Na(AlF6)] (Hawthorne some examples with face-sharing octahedra are and Ferguson, 1975). These include compounds known for antiperovskite polytypes, with anions 2– – – A2[B(TeO6)] with A = Ca or Sr and B =Ca or O ,F or Cl in the B sites (Krivovichev, 2008). Co (#566, 569–571) (Fig. 40), Cd2[Cd(TeO6)] The synthetic compound Ba2[Co(TeO6)] (#585) 4+ (#567), Na2[Sn (TeO6)] (#568)andA = disor- has very similar unit-cell parameters to #584 but a 3+ 3+ 3+ dered (Ca0.5Pr0.5), (Sr0.5Pr0.5) or (Sr0.5Eu0.5), B = different space group and structural topology. Li (#572–574). Unlike its analogues with Ca, Sr and Mn in B Sr2[Ni(TeO6)] has a larger 2 × 2 × 2 superstruc- sites (#576, 583 and 584 above), it is based on a 6H ture than the perovskites above, and C2/m sym- ABACBC stacking of BaO3 layers: the hkk metry (#575), although it is nearly cubic, with all sequence, where ‘h’ = ‘hcp-like (layers above and three cell parameters within 0.3% of their mean below superimposed)’ and ‘k’ = ‘ccp-like (layers value, and β ≈ 90.4°. The next five compounds above and below not superimposed)’. A very have the truly cubic ‘double perovskite’ structure of different 6H perovskite is described as #620, 2+ 6+ elpasolite (K2Na[AlF6]: Sabelli, 1987), with a 2 × below. Because layers of Co and Te cations 2 × 2 supercell but Fm3m symmetry. In all these alternate along z in #585, there are 12 oxygen layers compounds, Te alternates in the B sites in a altogether in the unit cell, which has space group ‘rocksalt’ fashion with Ni (#575), Ca (#576), Li P3m1, and two crystallographic types each of Co (#577–578), Mg (#579) or partially occupied Bi and Te. Co2 and Te2 octahedra each share one face (#580), while in #577 and 578, the alkaline earth with each other, while Co1 and Te1 share only 2+ 3+ cation Ba and lanthanides (La,Pr) are disor- corners (Fig. 40). In contrast, Ba2[Ni(TeO6)] dered in the A site, analogous to the situation in (#586) has a 12R (hhkk) layer sequence (space #572–574 above. group R3m), in which corner-sharing octahedra Our final group of perovskites have trigonal cells (Te1)O6 alternate along z with columns of three with a ≈√2 and c ≈ 2√3 times the edge of the face-sharing octahedra, Ni ≡ (Te2) ≡ Ni. Ba2[Cu fundamental perovskite cube. This is an alternative (TeO6)] (#587) has the same topology, but axial setting for a structure produced by compres- distortion of the CuO6 octahedra reduces the sion or extension of a 2 × 2 × 2 cube along one symmetry to triclinic P1. The distortion is not the [111] direction. The lattice type for such a usual symmetrical elongation, but gives Cu2+ five perovskite is R in most cases, but in oxygen neighbours at 1.98–2.11 Å and the sixth at Ba3[Bi2O3(TeO6)] (#581), the unusual ordering 2.26 Å. The triclinic (001) plane corresponds to pattern, with Te in only ⅓ of the B sites, reduces the (003) of the pseudorhombohedral cell, while the symmetry to P3c1 (Fig. 40). The space group is R3 pseudotriad axis is [113] in the triclinic axial or R3m for the other structures #582–584, which setting. A tetragonally distorted 3C perovskite have the standard ‘double perovskite’ cation polymorph of this compound was discussed at arrangement, and include the rhombohedral poly- #564, above. morph of Pb2[Co(TeO6)] (cf. #562 above). Three The next four closely-related compounds have additional compounds in the present study could be structures derived from the LiSbO3 type (Genkina, regarded as aberrant examples of rhombohedral 1992). This structure has a hcp oxygen substruc- double perovskites, but are more usefully consid- ture, as for the corundum superstructures of ered as superstructures of the corundum type. These LiNbO3 and NaSbO3, but a quite different are [Ni3(TeO6)] and its relatives, #599–601 below. arrangement of cations. LiSbO3 has an orthorhom- In the ABX3 cubic perovskite structure, the large bic structure with space group Pncn, which is cations A and anions X together form a cubic permuted into the Pnna axial setting here. Then,

504 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

6+ FIG. 41. Examples of structures with monomeric Te O6 anions as part of a larger structural framework (Table 23, deposited). Large spheres: Ba (yellow-green), Li (pale blue) and Na (dark yellow). Polyhedra: Cu (cyan), Mg (pale blue), Mn (magenta), Si (dark blue), Te (dark green), Zn (grey tetrahedra) and Zr (pale grey octahedra).

8 cell parameters a, b, c ≈√3, √( /3) and 3, octahedra do not form edge-sharing chains, but do measured in units of the mean ‘close-packed’ form face-sharing columns || y. Even in the O…O distance. There are two close-packed anion idealized structure, a and b are only ∼6% different, layers per cell (as opposed to six for corundum/ so the structure is metrically pseudotetragonal with ilmenite) || (020), and between each layer pair, Li pseudotetrad axis || z, and the two types of cation and Sb each occupy ⅓ of the octahedral interstices. are arranged similarly to Ca and W of the scheelite SbO6 octahedra form edge-sharing chains || x, and structure (Hazen et al., 1985), although the these share corners with the chains above and disposition of oxygen atoms is quite different. 4+ below to form a framework. The vacant octahedral The compounds Li2[M (TeO6)] (M =Sn or Ti; sites of each cation layer lie above and below Sb, so #588–589) have this structure, but with M and Te that SbO6 octahedra do not share faces. LiO6 alternating in the zigzag chains, which reduces the

505 A. G. CHRISTY ET AL. symmetry to Pnn2 (Fig. 40). Partial leaching of Li+ chain || x, with an adjacent zigzag of Li2 and Li3 on from the Ti compound and replacement with H+ one side. In the other layer, zigzag chains || x are indicated no structural change for small degrees of formed by Te2 and Mn4 and by Mn1 and Mn4. The leaching (Crosnier et al., 1992), but (H1.68Li0.32)[Ti vacancies of the second layer share faces with Te1 (TeO6)] showed considerable redistribution of non- and Mn2, while the vacancies of the first layer share Te cations, while preserving the (Te + O) substruc- faces with Mn1 and Mn3. The refinement indicates ture. A significant proportion of Ti occupied former some mixing (17%) of Li on Mn4 and of Mn on Li or vacant sites (#590), giving an arrangement Li3, but if this is ignored, all ‘Li’ sites excluded with the space group Pnnm, which is in effect a from the structural unit and all ‘Mn’ sites included, tri-CaCl2 (orthorhombically collapsed trirutile) then we define a framework in which layers of 2- structure. The structure of frankhawthorneite, wide and 4-wide octahedral ribbons share edges, [Cu2(TeO4(OH)2)], is closely related (#512 with channels between them || x which accommo- + 2+ 3+ above). Annealing of this compound re-ordered date Li ions. Na3[(Mn3 Mn )(TeO6)2](#598) has the octahedral site occupancies to give a tetragonal a ‘tri-harmunite’ structure which can be derived 3+ but acentric trirutile structure with space group from the Pnma structure of harmunite, CaFe2 O4 P42nm (#591). More conventional P42/mnm (Gaulskina et al., 2014), one of three closely related trirutile structures are covered below (#594–596). structures known to high-pressure researchers as Pb6[Co9(TeO6)5] and its Ni analogue (#592– ‘post-spinel’ phases, as they have the same cation: 593) have an unusual structure containing defect oxygen ratio as spinel but larger coordination 1 brucite-like layers with /6 of the cations missing, numbers, making them potential high-pressure 2+ (M7 Te 32)O24 (M = Co or Ni). These are con- polymorphs (cf. Yamanaka et al., 2013). These nected into a framework through additional M ≡ Te structures all have frameworks made by corner face-sharing dimers, which share corners with the sharing between 2-wide edge-sharing ribbons of layers above and below to form a pillared-layer octahedra, with channels which contain CN8 structure with very large interlayer channels, which cations (Fig. 41). In #598, the octahedral ribbons 3+ contain the Pb atoms (Fig. 41). [M2 (TeO6)] with run || y, but ordering of Te and mixed-valence Mn M = Cr, Fe or Ga (#594–596) have the well-known triples the unit cell repeat in this direction. Na trirutile structure also known for minerals such as occupies the CN8 site. Note that the octahedral 2+ 5+ the byströmite and groups, M Sb2 O6 (M ribbons define oblique, stepped slices of cations in 2+ 5+ = Mg or Zn) and M Ta2 O6 (M = Fe or Mn) an hcp anion array, repeated by twinning on (020), (Byström et al., 1942). The space group is the same as noted by Hyde and Andersson (1989). The  as rutile, P42/mnm, while the c repeat is tripled due hexagonal close-packed planes are || (210) or (210) to cation ordering. An unsual acentric trirutile in alternate twin lamellae. The oblique hcp slices phase with M1‒M2‒ ordering along its pseudo- differ from those of frankhawthorneite etc (#512– tetrad direction was discussed above (#586). 515) in that the ribbon direction is parallel to an 2+ 3+ Li[Mn Mn (TeO6)] (#597) again has slightly octahedral edge, rather than perpendicular. distorted hcp of oxygen atoms, a pseudotetragonal [Ni3(TeO6)] (#599) has a hcp array of oxygen unit-cell metric, and cell dimensions very similar to atoms in which ⅔ of the octahedral interstices are #583–586 and #594–596 above. However, a greater filled in the same pattern as corundum, Al2O3. proportion of the octahedral sites are occupied, However, alternate cation layers along the z although it should be noted that irregularity of the direction are either all Ni or are Ni+Te, ordered so octahedra and off-centring of cations mean that the as to reduce the symmetry to the polar space group coordination number is unambiguously 6 only for R3. The resulting structure is a superstructure not Te1, Te2 and Mn1–3, while Mn4 and Li2 are CN7 just of the corundum type (R3c), but also of its two and Li3 is CN8, if all cation–oxygen distances zellengleich 1 : 1 superstructures: ilmenite (FeTiO :  3 within 3 Å are included. Bond-valence sums using R3) and LiNbO3 (R3c). Ilmenite-structure com- the parameters of Brese and O’Keeffe (1991) pounds in which there is alternation of cation layers indicate that Mn1 and Mn3 are Mn2+, while Mn2 with Na and with disordered (M4+ +Te6+)are and Mn4 are Mn3+. The approximate close-packed discussed below at #664–665. The compounds 4+ oxygen layers are || (002), with the pseudotetrad Li2[M (TeO6)] (M = Zr or Ge; #600–601)are direction || y. Cations are arranged such that two out placed here because they are isopuntal, although of every three sites are occupied along the y cation layers of (Li1 + M) and (Li2 + Te) now direction. Two types of cation layer alternate. In one alternate along z. Lithium octahedra share faces of these, Te1 and Mn2 share edges to form a zigzag with M or Te octahedra, and the Li cations are

506 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS displaced strongly away from these neighbours strong and weak bonding is set at Cu–O = 2.2 Å, along z, in accord with the polar symmetry of the except for Cu2, which is 4+3 coordinated, with three structure (Fig. 41). If the low-valence Li atoms are oxygen ligands in the range 2.5–2.8 Å. Two Zn excluded from the structural unit, the remaining atoms are 4-coordinated and two are 5-coordinated. MTeO 6 framework has a rhombohedrally stretched The mineral mcalpineite has been recently version of the ‘double perovskite’ type. The c/a redefined as anhydrous [Cu3(TeO6)] (Carbone ratio is 17% larger in #601 than the value of √12 et al., 2013). It is interesting to note that its which would correspond to a primitive cubic structure (#609) is the explicitly ternary variant of arrangement of cations. As Li can be regarded as the ‘C-sesquioxide’ structure of heavy rare-earth 3+ an off-centre ‘A’ cation in the A2BB’X6 double and the bixbyite group of minerals M2 O3, perovskite topology, these compounds could in fact where M = Mn, Tl, Y and Sc, in respectively, be classified with the rhombohedral double per- bixbyite (Zachariasen, 1928), avicennite (Radtke ovskites #582–584 above, which have similar cell et al., 1978), yttriaite-(Y) (Mills et al., 2011) and dimensions. Thus, the range of cation valences in kangite (Ma et al., 2013) (Fig. 41). This is another these compounds, and the resulting choice of structure like the pyrochlore type (cf. #366, 700) whether or not to include cations in the structural which can be regarded as a defect fluorite. Again, unit, highlight a relationship between perovskite the overall cation array is cubic close-packed and and corundum structure families which is not there is a cubic unit cell with a ≈ 10 Å, correspond- otherwise obvious. ing to 2 × 2 × 2 fluorite unit cubes, but this time, ¼ [Mg3(TeO6)] (#602) is an archetype for several of the anions are missing, which correspond to O2 isostructural tellurates of Mn, Mn+Cu or Cd+Mn in the winstanleyite structure (#369–373), which (#603–605). The rather dense structure is not has similar cell dimensions and the same Ia3 space conventionally close-packed, but the key to com- group. As in winstanleyite, the cations are split into prehending it is to note that the rhombohedral cell two distinct types in a 3:1 ratio. All cations are 6- 6+ parameters for Mg are arh = 6.047 Å and αrh = coordinate in mcalpineite, but one type (Te , here) 90.86°, with Te atoms forming an almost perfect has a coordination polyhedron that is close to body-centred cubic array (more precisely a CsCl- regular octahedral geometry, while the other (Cu2+) type array, as there are two nonequivalent Te atoms has a less regular geometry that is best described as per cell) (Fig. 41). Like [Hg3(TeO6)] (#548) and the twisted trigonal prismatic. Up to half the Cu may be tellurate garnets (#549–553) above, these com- substituted by Co or Zn, with no further ordering pounds have an oxygen-stuffed Cr3Si structure, (#610–612). Some Te-free synthetic isotypes are 2+ 3+ 4+ with oxygen atoms occupying a different set of also rich in Cu, such as the phases Cu2–xFe2xTi2–xO6 2+ 3+ 5+ tetrahedral interstices than those that they do in (Mouron et al., 1985) and Cu2 M Sb O6 (M =Mn, garnets, such that each oxygen bonds to 3 Mg (≡Cr) Fe and Ga; Bazuev et al., 1994). and1Te(≡Si), while Mg and Te are all in Ba3[Zn6(Si2O7)2(TeO6)] (#613) has a unique octahedral coordination. There is no long-range zincotellurosilicate framework, with 9- and 12- 2+ order of Cd and Mn in [(Cd2Mn)(TeO6)] (#605). coordinate Ba ions in large cages. Paired ZnO6 The Co and Zn analogues have monoclinically and single TeO6 octahedra share edges to form distorted superstructures (#606–607). The Co and ribbons running || z that resemble the Cu2Te Zn compounds have space group C2/c, with octahedral ribbons of frankhawthorneite and amon ∼√3atrig, bmon ≈ btrig, cmon ≈ ctrig, β =92–95°. related compounds (#512–515). These ribbons are There are still two distinct Te sites per cell, but linked into a framework by sharing corners with 2+ the single octahedrally-coordinated M site of corrugated layers || (200) of ZnO4 tetrahedra and the rhombohedral phases splits into five distinct Si2O7 tetrahedral dimers. The tetrahedral layers sites with a wider range of coordination numbers: contain [Zn‒Si‒Zn‒Si] 4-rings and [Zn‒Si‒Si‒Zn‒ CN = 6, 6, 5, 6 and 4 for [Co3(TeO6)] (#606) and Si‒Si] 6-rings (Fig. 41). 3+ CN = 4, 4, 5, 5 and 6 for [Zn3(TeO6)] (#607). The [M6 (TeO6)O6](M = Y, In and Tl: #614–616) ordered Cu–Zn compound [Cu5Zn4(TeO6)3](#608) again have a defect fluorite structure like the has similar cell parameters, but additional displace- bixbyite isotypes #609–612 above, but the rhombo- ments of atoms which reduce the symmetry further hedral structure is more complex, with approxi- to C2. There are three Te sites, six Cu sites and four mately cubic close-packed cations ordered into two 1 Zn sites. While Te is in fairly regular octahedral types in a 6 : 1 ratio, /7 of the anions missing, and coordination, the Cu atoms are in Jahn-Teller the rest split into two types, coordinated either by distorted 4+2 coordination if the threshold between 2 M + 1 Te or by 4 M. All cations are 6-coordinate.

507 A. G. CHRISTY ET AL.

6+ FIG. 42. Examples of structures with monomeric Te O6 as part of a larger structural framework (#618, Table 23, deposited) and with soro dimers of TeO6 octahedra (Table 24). Small spheres: C (black), H (pale pink), N (brown) and O (dark pink) when not part of a polyhedron. Medium spheres: Si (blue) and Cl (yellow-green). Large spheres: K (purple) #635 and Pb (grey). Black triangles in :CO3 groups. Polyhedra: As (brown-green), Co (magenta), Li (grey-blue) and V (bright blue).

This structure is also known for compounds such as This section concludes with two Co-rich 6+ 2+ Y6(U O6)O6 (Bartram, 1966), the meteoritic frameworks. Na5Co15.5(TeO6)6 ≡ Na2.5(Na2.5Co1.5) mineral allendeite, Sc4Zr3O12 ≡ [(Sc4Zr2)(ZrO6) [Co14(TeO6)6](#617) has a nanoporous hexagonal O6] (Thornber et al., 1968; Ma et al., 2014) structure in which Co1 and Te octahedra share 3+ 4+ 4+ and Pr7O12 ≡ [(Pr4 Pr2 )(Pr O6)O6] (von Dreele edges to form 2-wide ribbons running || z. These 1+ et al., 1975). Remarkably, Tl6 [TeO6](#445, ribbons link at corners to delineate relatively large above) has the same space group and cation hexagonal tunnels (diameter ≈ 6.5 Å) and smaller substructure, and very nearly the same cell ditrigonal tunnels, which are internally braced by 3+ parameters as Tl6 (TeO6)(#616). However, all the Co2 atoms in trigonal prismatic coordination, to 8– non-tellurate oxygen atoms are missing in #445, complete a framework [(Co1)12(Co2)2(TeO6)6] . and the Tl–O bonds to the remaining oxygen atoms An additional site in the small channels is occupied are longer and less regular. by mixed Na + Co, while the remaining Na+ ions

508 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

2+ are in the large channels. [Co8 (TeO6)(AsO4)2O2] K4[Te2O6(OH)4]·5H2O(#624) has a simple but (#618) has four types of Co2+ ion (CN = 4, 6, 6 and incompletely determined structure in which dimers 6) sharing edges and corners to make thick double with Te=Te axes || x are linked into layers || (020) + layers || (020). TeO6 octahedra act as internal braces through K ions. Water molecules were not located, in the middle of the double layers, while AsO4 but are presumably in the interlayer gap and tetrahedra cross-link the layers into a three- complete the coordination polyhedra of the K+ dimensional framework (Fig. 42). ions. The structure of K4[Te2O6(OH)4]·8H2O (#625) is more completely determined, with all O and H atoms located, and bears little resemblance to Soro or cyclo finite polymers Te6+X that of its lower hydrate. Again, all Te=Te dimers m n are parallel (|| [011]), and lie in layers || (200), which 6+ Structures #619–645 contain Te O6 octahedra that alternate with layers of KO8–9 polyhedra. are linked into finite polymers TemXn (m =2–6); Rb4[Te2O6(OH)4] · 10H2O(#626) is somewhat these are listed in Table 24 (deposited). Our first similar, but in this triclinic cell, the layering is || two examples are closely related to each other. (110), Te=Te axes are || [214], and the Rb atoms are Ba3[Te2O9](#619) has a simple hexagonal struc- 8–10 coordinated and lie in less convoluted layers. ture containing the face-sharing dimer of Fig. 13a. Cs3[Te2O5(OH)5]·4H2O(#627) has one Te=Te These groups lie with ⅓ of the Ba2+ ions in layers || group per triclinic cell, aligned || [322], in a matrix (002), which alternate with layers containing the of water molecules and CN10 Cs+ ions, while 2+ 3+ 3+ 6+ other ⅔ of the Ba ions. Ba3[Fe ((Fe Te )O9)] Cs4[Te2O4(OH)4]·8H2O(#628) has a more obvi- (#620) has the same P6 /mmc space group and ously layered structure in which Te=Te groups 3  nearly identical unit-cell parameters. It contains the pointing || [212] and CsX9–10 polyhedra form sheets same dimeric anion, except that 50% of the Te6+ is || (101), which are linked only through hydrogen 3+ now randomly substituted by Fe , and charge bonds. K4Na2[Te2O8(OH)2] · 14H2O(#629) has a balance is maintained by insertion of additional Fe3+ body-centred array of Te=Te dimers pointing || z, ions into octahedral interstices which were vacant which bridge layers || (101) of water molecules, + + in #619. The additional Fe octahedra in #620 join CN8 K and CN6 Na ions. K7Na[Te2O6(OH)4]2 · corners with the face-sharing dimers to form a three- 12H2O(#630) has Te=Te dimers || x, lying in dimensional framework which is a 6H perovskite undulating layers || (020) that are connected weakly + + polytype, with hkk stacking of (BaO3) close-packed through CN6–10 K and CN6 Na ions. layers. It is thus very closely related to Ba2[Co The next two compounds are ditellurates of (TeO6)] (#585), where the different cation-ordering organic complexes. ((CH3)3Si)8[Te2O10](#631) pattern results in lower symmetry. The relationship to has a trimethylsilyl group strongly bonded (1 vu) these phases shows that #619 canbeconsidereda to each of the eight non-bridging oxygen atoms of defect 6H perovskite with ordered B-site vacancies. the Te=Te anion, to form a large neutral molecule Li4TeO 5 ≡ Li8[Te2O10] and its Na analogue that has only point symmetry 1, with two distinct Te (#621–622) has the edge-sharing dimeric anion of and eight distinct Si atoms. Four such molecules in Fig. 13b. All atoms are 6-coordinated, with each slightly different orientations pack together per unit oxygen atom linked to 5 Na + 1 Te or to 4 Na + 2 Te. cell (Fig. 42). (C(NH2)3)4[Te2O6(OH)4](#632)is The cation array is ccp and the structure is actually a not molecular, having well-defined guanidinium + superstructure of the rocksalt type, with the cations [C(NH2)3] and tellurate anions pseudocube edge vectors parallel to [0½½] and [Te O (OH) ]4–. However, the structure is surpris-   2 6 4 approximately 5 1 3 and 5 1 1 of the triclinic ingly complex, with four distinct C atoms and two [12 12 4] [ 6 3 12] cell in #622. The Te = Te dimer axes are oriented || types of Te=Te anion per unit cell. Te1 dimers [331] (Fig. 42). The Ag analogue (#623) has a pointing || [221] form layers || (100), which monoclinic structure in which layers of close- alternate with layers that contain both Te2 dimers packed cations stack || (004) in an ABAC sequence pointing || [211] and one type of guanidinium (alternating h and k layers). All cations and anions group. The other three types of guanidinium lie again occupy 6-coordinated interstices of the between the Te layers. + 6+ opposite substructure, so while Ag and Te of Two structures have edge-sharing Te2X10 the k cation layers are in octahedral coordination, (Fig. 13b) in combination with monomeric TeX6 + the Ag ions of h layers are in trigonal prisms. octahedra. K6[Te2O6(OH)4](TeO2(OH)4) · 12H2O Within the k layers, edge-sharing Te=Te dimers (#633) has Te=Te dimers (Te2) aligned || [110], alternate with Ag=Ag=Ag triplets along rows || x. alternating along z with monomeric octahedra

509 A. G. CHRISTY ET AL.

FIG. 43. Examples of structures with Te2O10 octahedral dimers as part of a larger structural layer or framework (Table 24, deposited) and of infinite chains of TeO6 octahedra (Table 25). Small spheres: O (dark pink) when not part of a polyhedron. Large spheres: Bi (violet), Ca (orange), K (purple), Na (dark yellow) and Pb (grey). Polyhedra: Cu (cyan), Ga (pale green) and Te (dark green).

(Te1). The rows of Te anions lie between layers || || [124] or [124], lying in sheets || (200). The Te  + (110) of CN8–10 K ions (Fig. 42). sheets have on each side of them PbO7Cl, PbO6Cl2 Cs2[Te2O4(OH)6] · (Te(OH)6)(#634) has Te=Te and PbO5Cl2 polyhedra which complete thick pointing || [211] and lying in layers || (001), layers, and carbonate groups and water molecules + which alternate with layers of CN9 Cs ions and lie between the layers (Fig. 42). K3[Ga neutral Te(OH)6 molecules. Note that this is a (Te2O8(OH)2)] · H2O(#636) has Te=Te dimers special case of an orthotelluric acid adduct, more alternating with GaO4 tetrahedra to form loop- conventional examples of which are described as branched vierer chains || z. The Te and Ga #376–431 above. polyhedra between them form ‘double-triangle’ Thorneite, Pb6[Te2O10](CO3)Cl2 ·H2O(#635, clusters; for a topologically similar chain made only see front cover image), has Te=Te dimers pointing of Te octahedra, see K2[Te3O8(OH)4] below (#658;

510 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

Fig. 13i). The chains form an approximately to two other dimers, as part of a [Ga‒Te‒Ga‒Te] hexagonal rod packing, and are held together 4-ring. The double triangles and 4-rings alternate, through CN7–8K+ ions and water molecules. forming crankshaft ribbons || z, which are arranged 1+ 2+ Tl6 [Cu (Te2O10)] (#637) has chains that are very in a centred-rectangular array and are connected similar in topology, but the non-Te component is a into a framework via the remaining Ga‒O‒Te links. CuO4 square rather than GaO4 tetrahedron. The The framework is very open, with 6–8 Å diameter four shortest Cu‒O distances are 1.96–1.98 Å, but a channels || x and z, which contain water molecules fifth neighbour to Cu at 2.52 Å provides an and CN9–11 K+ ions, and has very strong additional brace along the chain. The chains run pseudotetragonal symmetry in projection down x || x and are arranged in a chequerboard fashion, (Fig. 43). + leaving large square channels. Tl ions line Schieffelinite, Pb10[Te2O8(OH)3]2(TeO2(OH)4)2 the sides of these channels, and are in one-sided (SO4)·5H2O, and its chromate analogue 5+ 5–8 coordination. (NH4)2V TeO 6(OH) · H2O ≡ chromschieffelinite (#642–643), have as their 5+ (NH4)4[(V O2)2(Te2O8(OH)2)] · 2H2O(#638) structural unit the corner-sharing Te2X11 dimer of has a loop-branched dreier chain made from Fig. 13c. The Te–Te dimers lie in undulating layers regular Te octahedra and very distorted Voctahedra. || (020), with CN8–10 Pb2+ ions on either side. Edge-sharing Te=Te and V=V pairs alternate along Water molecules, additional TeX6 monomers and 2– 2– the chain || z. Every Te atom shares an oxygen orientationally disordered SO4 or CrO4 tetrahedra ligand with each Vof its adjacent dimer, and also a lie between the layers. CN3 oxygen atom with both of them. V–O We have two examples of cyclo anions made 6+ distances are 1.65–1.66 Å (non-bridging oxygen), from Te octahedra. K2[Te4O8(OH)10](#644) has 1.95–1.96 Å (CN2 bridging oxygen) and 2.16 and an edge-sharing pair of octahedra joining the two 2.47 Å (CN3 bridging oxygen), consistent with its halves of a Te4X18 ‘double triangle’ tetramer + description as the core of a [VO2] cation. The (Fig. 13d). These isolated clusters are arranged in + chains pack in a centred-rectangular array, with NH4 a herringbone pattern in layers || (100), with CN10 + ions and H2O molecules between them (Fig. 42). K ions between the layers. K8.5(H3O)0.5[Te6O18 Eckhardite, Ca2[Cu2(Te2O10)] · 2H2O(#639) (OH)9] · 17H2O(#645) has ditrigonal rings Te6X27 has TeO6 and CuO4+2 polyhedra sharing edges to in which Te octahedra alternately share corners and form layers || (101). The Cu ligands form a slightly edges with their neighbours (Fig. 13e). Rings are in twisted square at 1.96–2.02 Å, plus two more two different orientations with the ring plane completing an elongated octahedron at 2.51 and always normal to z, and form pseudohexagonal 2.67 Å (Fig. 43). The oxygen atoms associated with columns running || z, which are arranged in a all these polyhedra form a stepped, oblique slice hexagonal rod packing, with hydronium and through a hcp array, somewhat similar to the layer CN6–11 K+ ions between them. Successive layers seen in the frankhawthorneite-related structures of the rods || (200) are shifted by 1c, which reduces 4 #512–515 above. However, while the frank- the symmetry to monoclinic. hawthorneite layer ‘steps’ are edge-sharing ribbons which alternate between two octahedra in Infinite polymers Te6+X width (Cu=Cu) and one (Te), the eckhardite ribbons m n alternate between three octahedra (Cu==Cu) and Inotellurates two (Te=Te) in width. These run || y. Between the In structures #646–677 Te 6+ octahedra are linked to 2+ layers lie CN7 Ca ions. Ag[(UO2)(Te2O8(OH)2)] form infinite polymers (Table 25, deposited). Our (#640) has edge-sharing ribbons of UO7 pen- first examples of ino tellurates have edge-sharing tagonal bipyramids running || x, which share CN3 zweier chains Te2X8. In all cases, the shared edges oxygen atoms with Te2O10 dimers to form layers || of an octahedra are not cis to one another, so the (020). The layer topology contains ‘double- chain zigzags (Fig. 13f ). The database includes + triangle’ clusters U < (Te=Te) > U. The Ag ions two polymorphs of Na2TeO 4 ≡ Na4[Te2O8]. The are in irregular 5-fold coordination between the Pbcn polymorph (#646) has Te chains || z, arranged layers. In K2[Ga2(Te2O10)] · 2H2O(#641), GaO4 in a centred-rectangular array. The chains are tetrahedra and Te2O10 octahedral pairs share flanked by edge-sharing ribbons of NaO6 poly- corners to form a three-dimensional framework. hedra which hold the structure together. Overall, the Two ligands of each Ga connect it to a neighbour- oxygen arrangement approximates hcp, with close- ing Te = Te dimer as part of a ‘double triangle’ Ga < packed planes || (200) and (Na+Te) occupying ¾ of (Te = Te) > Ga, while the other two ligands link Ga the octahedral interstices between each pair of

511 A. G. CHRISTY ET AL. layers. The P21/c polymorph (#647) has a slightly O4(OH)6](#653) has such chains running || z of sheared version of the same sructure, with xmon = the tetragonal structure, with bridging oxygen 3 1 0 and z =[110] . The isostructural atoms disordered on a quadruply split site. Large [2 2 ]orth mon orth pair of compounds CaTeO4 and SrTeO4 (#648– square channels between the chains accommodate + 649) have the same space group as #646 (Pbcn, K ions in 8-fold coordination. NaBiTeO5 ≡ although strongly pseudo-Cmnm), very similar cell Na2Bi2[Te2O10](#654) has zweier Te 2O10 chains parameters, and the same type of Te chain. running || x, which form a pseudohexagonal array. However, only half of the Na sites of #646 are Sodium and Bi atoms occupy trigonal prismatic occupied by alkaline earth cations. (Ca,Sr)O6 and interstices between Te atoms; both form zigzag TeO 6 octahedra together form open-branched chains || z, and are ordered in a chequerboard zweier chains of edge-sharing octhedra running || fashion. The Te(NaBi) cation array is similar but z between each pair of close-packed anion layers, not identical to the ordered form of the CeCu2 type thus avoiding shared faces between (Ca,Sr) octa- (Larson and Cromer, 1961), apart from the strong hedra. This structure is shared with the pucherite monoclinic shear (β = 106.8°) of the structure in polymorph of BiVO4 (Qurashi and Barnes, 1953) #654. The oxygen coordination number of both Na and alumotantite, AlTaO4 (Ercit et al., 1992) as and Bi is 7 (Fig. 43). The mineral ottoite, well as synthetic MUO4 (M = Cr, Fe and Ni; Pb2TeO 5 ≡ Pb4[Te2O10](#655) has a very similar Hoekstra and Marshall, 1967). A Te-rich variety structure but with monoclinic shear much smaller of raspite, Pb[(W0.56Te 0.44)O4](#650) is included (β = 91.3°) and in a different direction (y and z are in this review, as the W:Te ratio is close to 1:1. reversed relative to #654) and Na and Bi positions Raspite is ideally PbWO4 (Fujita et al., 1977), merged into a single Pb site (Fig. 43). The Pb is in and was discussed earlier, as one of the forms of irregular 7-coordination (Pb–O = 2.37, 2.37, 2.53, 4+ 4+ 4+ Te V O4 is isostructural (#82, above). While Te 2.59, 2.71, 2.88 and 3.04 Å; no others at <3.4 Å). may occupy large, irregularly-coordinated sites like Hg2TeO 5 (#656) has cell parameters quite close to Pb2+, also a cation with a stereoactive lone pair, Te6+ those of ottoite, and the structure looks very similar readily enters octahedral sites, and so behaves in projection down x. However, the symmetry is analogously to W in raspite or V in TeVO4. The now orthorhombic (Pna21). The Te chains are raspite structure is a monoclinically sheared displaced along x so that the Te substructure has derivative of the pucherite type, in which the elongate octahedral and tetrahedral interstices anion arrangement is strongly perturbed away from rather than trigonal prismatic ones, and Hg atoms hexagonal close-packing and the larger cation is are split into two distinct types, both of which lie at irregularly 7-coordinated. The P21/a axial setting the centres of Te triangles. Both Hg atoms have 7 can be related back to the Pbcn setting of pucherite oxygen neighbours within 3.1 Å, but the bond- through the relations xpuch = zrasp, ypuch = [101]rasp length variation is such that Hg1 coordination is and zpuch = yrasp; a pucherite-like cell for raspite best regarded as plane-triangular (Hg–O at 2.13, would have space group P1121/n, a = 5.59 Å, b = 2.21 and 2.31 Å; no more until 2.49 Å) and Hg2 as 13.03 Å, c = 5.02 Å and β = 96.1° (Fig. 43). linear 2-coordinate (Hg–O at 2.07 and 2.08 Å, with KTeO3(OH) ≡ K2[Te2O6(OH)2](#651) has similar no more until 2.53 Å). Because of the large bond cell parameters to #646–649 and a very similar valence of the short Hg–O bonds, this structure is arrangement of Te chains, although chains in regarded as having a Hg‒Te heteropolyhedral successive layers || (020) are translated by 1a framework. 2 relative to their positions in the pucherite structure, Ag3TeO 4I ≡ Ag9[Te3O12]I3 (#657) has an edge- the K atoms are near positions that are vacant sharing dreier chain Te3X12 in which again the octahedra of (Ca,Sr)TeO4 and are in 7- rather than shared edges are not trans (Fig. 13h). The chains 6-coordination, and the symmetry is monoclinic spiral helically || y, and are surrounded by nine + P21/a, but this time not as a subgroup of pucherite types of Ag ion so as to form thick layers || (200), – symmetry. (NH4)TeO3(OH) (#652) has a triclinic with I anions in the interlayer gaps. Ag atoms are distortion of this structure with x = [011] and irregularly coordinated by 3 O + I, 2 O + 2 I, O + 3 I  orth tcl yorth = [011]tcl. or 2 O + I. K2[Te3O8(OH)4] and its NH4 analogue The corner sharing zweier chains Te2X10 of the (#658–659) have a quite different Te3X12 chain, present study all have their bridging oxygen atoms with a Q2400 octahedron alternating with a pair of trans to each other across a Te octahedron, but Q2401 octahedra to make a loop-branched zweier zigzag nevertheless due to having non-linear Te– type as seen in Fig. 13i. This chain represents a O–Te links (Fig. 13g). KTeO2(OH)3 ≡ K2[Te2 condensation of the ‘double triangle’ cluster that is

512 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

FIG. 44. Examples of structures with TeO6 linked to form infinite layers or frameworks (Table 25, deposited). Small spheres: H (pale pink). Large spheres: Ca (orange), Li (pale blue), Na (dark yellow) and Pb (grey). Polyhedra: Cu (cyan), Fe (orange-brown) and Te (dark green). There is substantial Fe–Te disorder in #677.

2+ seen in isolation in K2[Te4O8(OH)10](#644, chains all are || x, and linear 2-coordinated Hg Fig. 13d). Eight such chains per unit cell run || z link the chains to form layers || (002). Ag atoms lie and pack in a herringbone arrangement, held between the layers in irregular 6-coordination. together by large cations in 8-coordination Li2TeO 4 ≡ Li8[Te4O12](#662) has a chain that is (Fig. 43). Similar chains of double triangles occur the vierer analogue of the dreier chain in #657. This in Ag2TeO 4 ≡ Ag6[Te3O12](#660) and time, the nonlinear Te=Te=Te links result in a Ag2[Hg2(Te3O12)] (#661). In the first of these helical chain with periodicity four (Fig. 13j), which compounds, the pseudotetragonal cell has chains spirals around a screw tetrad axis in the structure, that lie in layers || (002), and chains run || [110] or winding through a matrix of LiO tetrahedra. Our  4 [110] in alternate layers. Silver atoms lie between final inotellurate is the mineral housleyite, Pb6[Cu the layers in 2–4 coordination. In #661, the Te (Te4O18(OH)2)] (#663), in which the vierer chain is

513 A. G. CHRISTY ET AL.

3+ 6+ entirely corner-sharing, but differs from the zweier Burckhardtite, Pb2[(Fe Te )O6][AlSi3O8](#666) 3+ 6+ 3– chain of ottoite (#655) in that there is alternation of has [(Fe Te )O6] layers of the same type, Te octahedra with trans bridging oxygen atoms and alternating with aluminosilicate double layers – octahedra with cis bridging oxygen atoms [AlSi3O8] of the topology seen in minerals such (Fig. 13k). Tellurium chains run || [101], and are as cymrite, Ba[Al2Si2O8]·H2O (Drits et al., 1975). 4+ 6+ linked through CuO4+2 polyhedra to form corru- Sr[(Mn Te )O6](#667) has a hexagonal cell gated layers || (101). Copper shares corners with with a parameter similar to those of #664–666, and two adjacent Te octahedra in the chains on each a c parameter suggesting that it might be isotypical side, to make a pair of [Cu‒Te‒Te] 3-rings (Fig. 44). with rosiaite-type compounds such as The four shortest Cu–O distances are 1.96–1.97 Å; Sr[Ge(TeO6)] (#521 above), in which layers of Sr two more neighbours at 2.65 Å complete an octahedra alternate with layers of (M4+ + Te). elongated octahedron, and further brace the struc- However, the structural refinement reveals that tural layer. Pb atoms in irregular 7–8 coordination Mn and Te are disordered in trigonal prisms decorate the outsides of the layers and link them. (Fig. 14b) rather than in octahedra, which is Fortuitously, the structure has a pseudotetragonal reflected in the different space group, P62 m as aspect in projection down x, with the Te atoms opposed to P31 m for disordered rosiaite (e.g. appearing to form an apophyllite-like net of 4- and Pb[Sb2O6]) or P312 for ordered rosiaite (#521). 8-rings, but the component Te chains are linked [TeO2(OH)2](#668) has TeX6 octahedra sharing only through Cu atoms, so this pattern has little four corners with neighbours to form a slightly structural significance. crumpled square net (Fig. 14c). The layers are || (100), and are held together only by hydrogen bonds (Fig. 44). (Bi2O2)[TeO4](#669) has topo- Phyllotellurates logically similar but geometrically more regular The simplest layer tellurates have an edge-sharing square layers || (020), which intercalate with 2+ dioctahedral sheet MX3 of the topology seen in cationic sheets [Bi2O2] which have the litharge gibbsite and other polymorphs of Al(OH)3 structure (Boher et al., 1985). The two types of unit 6+ … (Fig. 14a). Note that a Te O3 sheet would be are held together by long Bi O bonds. [Cu(TeO4)] 2– electrostatically neutral and that a protonated sheet (#670) also has square [TeO4] layers || (020), but would be charged positively. In all the cases corner-sharing chains of CuO4 squares run || [101] described here, some of the M cations are a that share edges with TeO6 octahedra above or different element of lower valence than Te, thus below to link the whole structure into a strongly- achieving a negative charge on the sheet. What is bonded framework. The four shortest Cu–Oarein unusual is that even though the two elements are the range 1.90–2.12 Å, but the Jahn-Teller present in a 50:50 ratio in all cases, there is no elongation of the CuO4+2 octahedron is unusually evidence for long-range three-dimensional order of small, as the next neighbours are at only 2.22–2.26 Å. the cations. It is quite feasible that two-dimensional Alternation of Te6+ with U6+ in a square-net layer order occurs within the layers, but the M cations are such as those of #668–670 produces the heteropoly treated as disordered here in the absence of structural layer of markcooperite (#544–545 experimental evidence to the contrary. The iso- above). structural pair Na2[(GeTe)O6](#664) and Ca5[Te3O14](#671) has more complex corner- Na2[(TiTe)O6](#665) have the ilmenite (FeTiO3) sharing layers of the type shown in Fig. 14d, with structure, which is in turn a superstructure of the Q2400 and Q4200 octahedra. It is isotypical with corundum type. Oxygen atoms are hcp, and chiolite, Na5[Al3F14] (Jacoboni et al., 1981), although between each pair of layers, ⅔ of the octahedral with a slight orthorhombic distortion (chiolite is interstices are occupied either by Na or by tetragonal, P4/mnc). This compound thus represents disordered (M4+ +Te6+). Discrete layers || (003) another valence-doubled structural analogy between can be identified as structural units because of the tellurates and hexafluoroaluminates, along with weakly bonded Na layers that lie between them examples such as the perovskite-superstructure 5+ (Fig. 44). Brizziite, NaSb O3, is compositionally phases Ca3TeO 6 (#561) and cryolite, Na3AlF6 close and shares the same structure (Olmi and (Hawthorne and Ferguson, 1975), Ba2CaAlF6 Sabelli, 1994). A superstructure of the ilmenite (#571) and elpasolite, K2NaAlF6 (Sabelli, 1987), type, in which additional cation ordering results in and the garnet-structure minerals yafsoanite, isolated TeO6 octahedra, occurs for Ni3(TeO6) and Ca3Zn2(TeO6)2 (#587) and cryolithionite, its relatives, discussed as #599–601 above. Na3Li2(AlF6)2 (Geller, 1971). In #671, tellurate

514 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS layers are || (002), with CN7–8Ca2+ ions lying layers are bridged further to link them in three between them (Fig. 44). Other fluoride-tellurate dimensions through additional Te1–Te3 and Te2– analogies were noted in the discussion of Fig. 14f–g, Te4 links, which create 4- and 6-rings. The Pb above. atoms in 7–8 lie between the dense layers coordination (Fig. 44).

Tectotellurates 2+ 6+ #672–673 [(Co Te )O4] and its Ni analogue ( ) Mixed-valence Te4+ and Te6+ have long-range disorder of the divalent cation and Te in octahedral sites, similar to the situation in the Table 26 (deposited) lists structures #678–703, phyllotellurates #664–667 above. However, in which feature Te in both +4 and +6 valence states. 2+ 6+ these compounds, the octahedra share two trans The first of these compounds, [Co6 (Te O6) 4+ edges and all corners to form a framework with the (Te O3)2Cl2](#678) is a somewhat trivial example 6+ 6– same topology as the rutile form of TiO2, but a in that it contains isolated [Te O6] octahedra and 4+ 2– strong monoclinic distortion (Fig. 14e). Thus, they [Te O3] trigonal pyramids. However, the structure 4+ are isostructural with tugarinovite, Mo O2 (Brandt is related closely to the interesting schafarzikite‒ and Skapski, 1967). The pseudotetrad direction is apuanite‒versiliaite polysomatic series of minerals. 2+ 3+ x, while vectors [010] and [½01] correspond to the Schafarzikite, Fe Sb2 O4, is isostructural with 4+ 2+ x and y lattice vectors of the tetragonal rutile cell. minium, Pb Pb2 O4 (Fischer and Pertlik, 1975; [TeO3](#674) has the rhombohedral FeF3 type of Gavarri and Weigel, 1975) and has rutile-like edge- structure (Hepworth et al., 1957) in which an sharing chains of octahedra containing Fe2+ octahedron shares each corner with a different running || z, connected through chains of corner- 2– neighbour (Fig. 14f ). Topologically, the structure is sharing lone-pair cations, [Sb2O4] . The overall the same as that of the cubic defect perovskite structure has the same tetragonal space group P42/ ReO3, but the Te–O–Te angles are reduced from mbc as #678, a = 8.59 Å and c = 5.91 Å. A series of 180° so as to collapse the structure and achieve additional phases is produced if some pairs of Sb3+ approximate hexagonal packing of oxygen atoms. ions and their lone pairs (Sb3+-::-Sb3+)arereplaced These and other related structures are discussed by by (Fe3+–S–Fe3+) bridges, with oxidation of some Hyde and Andersson (1989), and an analogous octahedral Fe2+ to Fe3+ in order to maintain relationship between stuffed variants of these electroneutrality (Mellini and Merlino, 1981). structures, namely the ilmenite/corundum structure Chemically, the maximally substituted 3+ and ABX3 perovskite, was discussed in connection end-member, with all Fe oxidized, would be (Fe2 ) 3+ with Ni3TeO 6 and its isotypes, #599–601 above. (Sb2Fe2 )O8(S). Versiliaite, with a c parameter Na2[Te2O7] and its Ag analogue (#675–676)have doubled relative to schafarzikite and with ortho- the same framework as weberite, Na2(MgAlF7) rhombic symmetry, represents 50% substitution, 2+ 3+ 3+ (Knop et al., 1982), depicted in Fig. 14g. The extra- (Fe2 Fe2 )(Sb6Fe2 )O16(3S), while apuanite, framework cations are in similar environments, Na with a tripled c parameter and P42/mbc symmetry, 2+ 3+ having eight oxygen neighbours at 2.26–2.79 Å has the 67% substituted composition, (Fe Fe2 ) 3+ while Ag–O distances are in the range 2.39–2.81 Å. (Sb4Fe2 )O12(2S). Compound #678 has very 3+ Pb3[Fe2 Te 2O12](#677) has partial ordering of Fe similar cell parameters to apuanite (for which a = and Te on four distinct octahedral sites. Te1 and Te2 8.37 and c = 17.97 Å) and is nearly isotypical with it, 6+ 2+ are (Te0.75Fe0.25), while ‘Te3’ and ‘Te4’ are actually as evident if its formula is written (Te Co2 ) 2+ 4+ (Fe0.75Te 0.25). Tellurium- and Fe-rich octahedra are (Co4 Te 2 )O12(Cl2). It thus represents an inter- related via a pseudo-a-glide reflection || (002). mediate member of a series between two hypothet- Here, all are considered as of equal status in the ical end-members, with the interesting structural unit. Te-dominant and Fe-dominant complication that it is not possible to write a octahedra alternate in the unique framework of formula that both makes crystal-chemical sense and Fig. 14h, which is strongly layered || (200). Within a is electrostatically neutral. The extreme composi- layer, zigzag zweier chains of Te2 and Te4 alternate, tions that correspond to those of the schafarzikite 6+ 2+ 1+ 2+ 2+ 4+ both running || z. The Te1 atoms share corners to family are [Te Co2 O4Cl] and [Co2 (Co2 Te 2 ) 1– make 3-ring loops on the Te4 chains, while Te3 do O12(Cl)] . The ordering of Co and Te is the same for the Te2 chains. The Te1 of one chain consistent with these, such that octahedral Co2+ is and Te3 of an adjacent chain then share edges, so as closely associated with pyramidal Te4+, while to make 8-rings and complete the layer, and the octahedral Te6+ is close to tetrahedral Co2+.The

515 A. G. CHRISTY ET AL.

4+ 6+ FIG. 45. Examples of structures containing both Te and Te (Table 26, deposited). Small spheres: H (pale pink). Large spheres: Cd (purple-pink), Hg (pale grey) and Sr (red). Polyhedra: Cu (cyan) and Te (dark green). The Te layers of #693 are further linked into a framework through linear O–Hg–O links, which are not shown for clarity. The Te6+ cations are in nearly regular octahedra; the Te4+ cations are not.

3+ 4+ structure of emmonsite, [Fe2 (H2O)(Te O3)3] ∼0.38 Å from the Te position, so as to acquire an (#137, above) is closely related. additional oxygen neighbour. The lone-pair cations It is noteworthy that there are no structures in and Te6+ link to form as a structural unit the loop- which Te4+ and Te6+ polyhedra are linked together branched zweier chain of Fig. 15a. Note that this is into a finite Te–O complex. The simplest Te–O a mixed-valence version of the chain that occurs in 6+ polymers that contain both valence states are K2[Te3 O8(OH)4](#658, Fig. 13i), and that both 3+ 4+ 6+ infinite chains. In Bi[(Bi Te )Te O8], #679, are built from the very frequently occurring half of the Bi atoms occupy 8-coordinated sites ‘double-triangle’ clusters. In #679, chains lie in (Bi1), while the other half (Bi2) randomly share a layers || (002), and chains of alternate layers run split site with Te2. The Bi atoms are displaced by either || [110] or || [110]. The Bi1 cations lie

516 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS between the chains and link them. Interestingly, Bi1 and have Te4+ (Te2) polyhedra making 3-rings with and octahedral Te1 also lie in layers, this time || adjacent pairs of octahedra. However, the layer is 4+ (200), and form a square net in which TeO6 completed by Te polyhedra linking to each other, octahedra share two trans edges with Bi atoms, to form (Te1‒Te2‒Te2‒Te2‒Te1) 5-rings (Fig. 15e) and the remaining corners with another two Bi (Fig. 45). The polymerization state of Te1 is Q2400 atoms. Layers of (Bi2, Te2) alternate with those of while that of Te2 is Q0400; the hydrogen atoms are (Bi1 + Te1). The structure can be regarded as an located on the non-bridging ligands of Te1, with extreme derivative of the fluorite type, given the 1:2 layers held together via both hydrogen bonds and cation:oxygen ratio, and the fact that cations lie in long Te2…O interactions. The polarity of the an approximate ccp array with pseudocube edge structure along z is due to the orientation of both vectors [00½], [010] and [¼0½] of the O‒H groups and Te4+ lone pairs. Polymorphs I and 4+ 6+ monoclinic cell, with lengths respectively 5.14, III of Ag2[Te Te O6](#686–687)havelayer 5.56 and 5.82 Å. topologies that are quite distinct from each other 4+ 6+ 4+ 6+ 4+ Cd2Te Te O7 ≡ Cd4[Te Te 2 O11](Te O3) and from that of polymorph II (#684). In poly- (#680) has two types of Te4+ (Te1 and Te3) and of morph I, layers are || (101) and contain ‘double- Te 6+ (Te2 and Te4). The Te6+ octahedra form the triangle’ clusters of Q1501 Te 6+ and Q1300 Te 4+, backbones of zweier chains || x, with Te3 attached to which link to form a net which has 8-rings as well them to form 3-ring loops (Fig. 15b). The as 3-rings (Fig. 15f ). Note that the positions of Te4+ 2– 6+ independent Te1 atom forms pyramidal [TeO3] and Te in the double triangle are reversed relative anions that lie between the loops. Te–O anions are to their locations in the chain of Bi[(Bi3+Te 4+)Te6+ embedded in a matrix of edge-sharing CdO6–8 O8](#679, Fig. 15a). Sheets of edge- and face- 4+ 6+ 4+ 6+ polyhedra. Cd2Te 2 Te O9 ≡ Cd4[Te2 Te 2 O12] sharing AgO6–7 polyhedra lie between the Te–O 4+ (Te O3)2 (#681) is rather similar, although the layers. The Te–O layer of polymorph III is very zweier tellurate chain is || y, has twice as many 3- similar, but is oriented || (100) in its structure, and ring loops (Fig. 15c) and twice as many associated an additional short Te4+–O distance of 2.41 Å but separate tellurite pyramids. The chains lie en renders all oxygen ligands as ‘bridging’ and breaks échelon in well-defined layers || (100), which the 8-rings into pairs of 4-rings (Fig. 15g). The Ag+ alternate with layers of edge-sharing CdO7 poly- ions between the layers are in irregular 5–6 hedra (Fig. 45). The tendency of Cd2+ ions to form coordination. rather complex structures was noted previously There are a number of polytypical compounds 2+ 2+ 4+ 6+ (#327 and 334, above). with the formula A [M (Te Te O7)], where A = 4+ 6+ (NH4)[Te Te O5(OH)] (#682) has infinite Sr, Pb or Ba and M =Cu(#688–690), Mg (#691)or 6+ Te–O layers || (002) in which Te O6 octahedra Zn (#692). All structures have similar-sized unit share corners to form zweier chains || x, and CN5 cells. The symmetries are primitive but centrosym- Te 4+ share corners with two octahedra from each of metric Pbcm for one polytype (#688–689)orcentred a pair of chains to form a net with 3- and 4-rings but without inversion symmetry for the other (#688– (Fig. 15d). Thus, the layer contains looped chain 689); the Ama2 space group used for the latter elements similar to the anions of #680–681.Te6+ subgroup has x and z directions reversed relative to octahedra are Q0600, while Te4+ polyhedra are Q1400 the P subgroup, and would be written C2cm in the + 2400 6+ in connection pattern. NH4 cations lie between the same axial setting. In #688,Q Te octahedra layers. The OH– group was not located, but is (Te1) share cis corners to form zigzag zweier chains || presumably the unique non-bridging anion attached z. Each octahedron also shares another pair of trans 4+ 4+ 6+ 2200 4+ to Te . Ba[Te Te O6](#683) has a topologically cornerswithQ Te (Te2) to make zigzag chains identical Te–O layer || (020), with Te6+ chains || x, thus forming strongly corrugated layers || (020) running || z. The Ba2+ ions between the layers are in with four 6-rings meeting at each Te6+ cation 10-coordination. The third structure with this layer (Fig. 15h). The M cations, Cu in this case, are in 4+ 6+ topology is polymorph II of Ag2[Te Te O6] square-pyramidal 5-fold coordination above or (#684). In this monoclinic structure, the Te–O below the Te sheet, and share corners with three layers are || (001) with Te6+ chains || y, and layers are Te1 atoms of one chain and two adjacent Te2 atoms, connected through sheets of Ag+ ions in irregular 6- producing a structural unit that is a rather dense fold coordination. Two other polymorphs are double layer (Fig. 45). The positioning of the Cu 4+ 6+ described below (#686–687). [Te Te O4(OH)2] atoms is the main topological factor that gives the (#685) has layers || (200) which again contain layer a polarity along the x direction. The Sr2+ ions zweier chains of Te6+ octahedra (Te1), || z this time, lie between the layers in 10-coordination. In this

517 A. G. CHRISTY ET AL. polytype, layers stack along y so that Te1 chains of Half of the Te‒O‒Te links in these sheets are successive layers superpose, but the polarity along x decorated by Te4+ (Te2) so as to form (Te1‒Te1‒ reverses from layer to layer. In the C2cm polytype, Te2) 3-rings, which define loop-branched zweier there is a displacement of 1a between adjacent layers, chains (cf. #681) running || y. The Te2 cations 2 but the polarity is the same for all of them. The β and associated with adjacent Te1 sheets then share 2+ 4+ 6+ α polymorphs of [Hg2 (Te Te O7)] (#693–694) remaining ligands with each other to link the sheets also have Te–O layers with the topology of Fig. 15h. together; thus, the Te2 polyhedra in isolation form The layer in the β phase is corrugated very similarly corner-sharing chains with a massicot-like geom- to that of #688–692, while that of the α phase is etry (Hill, 1985) (Fig. 45). 6+ 4+ 6+ much flatter, as the Te octahedra are connected Carlfriesite, Ca[Te2 Te O8](#697) has a nano- through trans corners. The β phase (#693) has layers porous framework that contains loop-branched || (002), with chains of Te6+ running || x. There are vierer chains of 4-rings, with Q2400 Te 6+ at the five types of Hg atoms between the layers, linking nodes linked through Te4+ on the loops, that run || z them into a framework. All Hg atoms have two and are flattened || (010). A centred-rectangular close oxygen neighbours at 2.03–2.31 Å. However, array of such chains is linked by Te4+ of while there is a distinct gap in distances before next- neighbouring chains sharing edges to form a nearest neighbours for Hg1, Hg2 and Hg4, this is framework with ∼6 Å wide channels || z, which not true for Hg3 or Hg5, which have six neighbours contain CN8 Ca2+ ions (Fig. 16b) (Fig. 46). The Sr 4+ 6+ in the ranges 2.24–2.38 and 2.30–2.36 Å, respect- analogue, Sr[Te2 Te O8](#698) has a quite ively (Fig. 45). This wide range of stereochemistries different tetragonal structure which contains for Hg in the same compound is not unusual. chains of ‘double-triangle’ clusters similar to Mercury and Te atoms form approximately close- those in #679 above (Fig. 15a). These chains run packed layers || (080), which form two repeats of the || z and share corners to produce a framework with four-layer ABCB sequence along y. Within each narrow (∼4 Å) channels, which contain CN8 Sr2+ layer, Te and Hg alternate in the z direction, while ions (Fig. 16c). Te 4+ and Te6+ alternate along y in the corrugated Te The remaining structures all feature Te polyhedra layers. In the α phase (#694), layers are || (202) with that share corners to form the hexagonal tungsten Te 6+ chains || y. Mercury atoms between the layers bronze or kagome net of hexagons and triangles, are of four different types, each with two close and all have at least one ∼7.3 Å unit-cell parameter oxygen neighbours at 2.05–2.28 Å and no more which corresponds to the repeat unit of that net. 4+ 6+ until 2.40–2.73 Å. Mercury and Te atoms lie on a Ag2[Te2 Te 2 O11](#699) has a strongly pseudo- ccp array, ordered layer-wise in a CuAu-type hexagonal but intrinsically triclinic structure. Te1 fashion. Cubic pseudocell edge vectors are and Te2 (CN6 Te6+) and Te3 (CN5 Te4+) form two [¼½¼] and [¼½¼] ¯ (5.20 Å long) and [¼0¼] ¯ layers of kagome type || (001), which share corners (5.43 Å), with layers of Hg and Te alternating || but are offset relative to each other. These double (202) and Te4+ and Te6+ alternating along [101] layers are then linked into a framework via edge- within the Te layers. sharing Te4 = Te4 dimers of CN5 Te4+, which form 4+ 6+ [Te3 Te O9](#695) has a rhombohedral struc- additional 3-rings with Te1 and Te3 above and ture with layers || (003) of the form shown in below (Fig. 16d). The Ag+ ions, in irregular 6–8 Fig. 15i. Rings of six Q0400 Te 4+ polyhedra coordination, lie in the hexagonal rings of the surround ⅓ of the triad axes, which are linked kagome layers, and between rows of Te4 atoms 0600 6+ 4+ 6+ through Q Te octahedra which are located on (Fig. 46). Cs2[Te Te 3 O12](#700) has a rhombo- the remaining triads. The resulting net has 3-, 4- and hedrally distorted pyrochlore framework (Fig. 16e). 6-rings, such that the ring pattern around Te4+ is Both valence states of Te are in nearly regular 6.3.4.3, while that around Te6+ is 3.4.3.4.3.4. octahedral coordination, which is extremely Layers are held together only through long unusual for Te4+, although it is also found in the 4+… 4+ Te O bonds (Fig. 45). pyrochlore Pr2[Te2 O6]O (#366 above). Note that 4+ 6+ 4+ [Te Te O5](#696), like #695, has CN4 Te the lone pair of electrons is not stereochemically and CN6 Te6+ sharing all vertices of their active in these compounds. When it occurs, coordination polyhedra, but for this compound, stereoactivity usually causes strong distortion of 4+ the resulting structure is a three-dimensional the Te O6 polyhedra (cf. Christy and Mills, 2013). framework (Fig. 16a). The Te6+ octahedra (Te1) Ordering of Te4+ and Te6+ in the octahedral sites is share four vertices with other Te6+ cations to form the cause of the symmetry reduction from cubic. As sheets of 4-rings || (001), as found in #668–670. is typical for ‘inverse pyrochlores’, the very large

518 H TUTRLACIETR FTLUIMOXYCOMPOUNDS TELLURIUM OF ARCHITECTURE STRUCTURAL THE

TABLE 27. Unit-cell data and references for additional minerals, where no structure refinement is available.

Compound (Mineral name) SG a/Å b/Å c/Å α, β, γ/o Reference 2+ 3+ 4+ Mg0.5 [(Mn Fe )(Te O3)3] · 4.5H2O P63/m 9.451(7) 9.451(7) 7.687(9) 90, 90, 120 Miletich (1995a) (Kinichilite) 2+ 3+ 4+ Mg0.5 [(Ni Fe )(Te O3)3] · 4.5H2O P63/m or P63 9.344(2) 9.344(2) 7.607(3) 90, 90, 120 Miletich (1995a) (Keystoneite) 2+ 3+ 4+ Mg0.5 [(Zn Mn )(Te O3)3] · 4.5H2O P63/m 9.40(2) 9.40(2) 7.657(17) 90, 90, 120 Pekov et al. (2015) (Ilirneyite) 4+ 519 Cu(Te O3)·2H2O P21/c 7.4049(2) 7.7873(2) 8.5217(2) 90, 110.203(3), 90 Rumsey et al. (2016) (Millsite) 3+ 4+ [Fe2 (H2O)3(Te O3)3]·3H2O P21/c 16.9356(5) 7.8955(3) 10.1678(3) 90, 98.006(1), 90 Back et al. (2011) (Telluromandarinoite) 4+ 6+ 6+ (K1.5 □0.5 )[(Te1.25 W0.25 □0.5 )W5 O19 ] Pban 7.2585(4) 25.8099(15) 3.8177(2) 90, 90, 90 Li et al. (2014) (Tewite) 4+ 6+ PbMn (Te O6) orth. C? 5.11(1) 8.91(1) 5.32(1) 90, 90, 90 Yablokova et al. (1975) (Kuranakhite) 4+ 6+ Ca2Mn2 (Te O6)2 ·H2O P2/m, P2, or Pm 10.757(3) 4.928(3) 8.492(2) 90, 102.39(3), 90 Grundler et al. (2008) (Xocolatlite) Pb3[Zn3(TeO6)(VO4)2] orth. C? 8.58(3) 14.86(5) 5.18(3) 90, 90, 90 Kim et al. (1990) (Cheremnykhite) 6+  Pb2[Cu2(Te2 O10)] · 2H2O P1 5.322(3) 7.098(4) 7.511(4) 83.486(7), 76.279(5), 70.742(5) Kampf et al. (2016) (Andychristyite) A. G. CHRISTY ET AL.

+ 3+ 4+ Cs cation occupies the Y site of the A2B2X2Y Fe2 (Te O3)3 ·6H2O(Backet al., 2011), is the pyrochlore pattern, while the CN8 A sites are Te analogue of the selenite mineral mandarinoite, 4+ 6+ vacant. The K analogue of #700,K2[Te Te 3 O12] and has similar symmetry and unit-cell dimen- (#701) has a variant of the same structure that is sions. If the two minerals are isostructural, then 2– monoclinically sheared. The monoclinic cell axes two symmetrically distinct [TeO3] pyramids correspond to the hexagonal axes of #700 as share corners with FeX octahedra to form layers ||  6 follows: amon =[110]hex, bmon = bhex, cmon = (100) with 8-rings of alternating Fe and Te, which [⅓⅓⅔¯ ]hex. The distortion reduces the coordination are bridged by a third type of TeO3 grouptoform 4+ number of Te from 6 to 5 (Fig. 16f ), which allows averyopen[M2Y3(TeX3)3] framework with the lone pair to become stereoactive, and the additional water molecules in large cavities (cf. coordination number of K+ decreases from 12 to 10. Hawthorne, 1984). Such a structure would follow 4+ 6+ 5+ The compound (Na1.6Ag0.4)[Te2 Te 3 O14](#702) Sb2 O3(TeO3)2 (#147) in our tables. The full has kagome layers of Te6+ octahedra || (100), which description has not yet been published for the 4+ 6+ 6 are linked through corner-sharing dimers of CN4 mineral tewite, (K1.50.5)[(Te1.25W0.250.5)W5 4+ + Te polyhedra (Fig. 16g) in a manner reminiscent O19], but the W-rich composition suggests that it of the linkage via edge-sharing CN5 dimers in #699 is a tungsten bronze-like phase containing layers of 4+ above. Again, the Te dimers form 3-rings with corner-sharing WO6 octahedra, with layers oriented pairs of Te6+ octahedra in the kagome layers above normal to the very short (3.8 Å) c repeat, along which and below, and weakly bound 8-coordinated W–O–W links connect them into a framework. There cations (Na,Ag) lie in the hexagonal holes of the may be some modification of the kagome net due to kagome net and between the Te4+ dimers. The replacement of some W by Te4+ with stereoactive ordered distribution of the interlayer (Na,Ag) and lone-pair electrons, as in structures #699–703 above. an associated undulation of the kagome layers Note in particular that a ≈ 7.3 Å and b ≈ 25.8 Å are results in the very long (∼25 Å) b repeat (Fig. 46). very similar to a ≈ 7.3 Å and b ≈ 24.7 Å for 4+ 6+ 4+ 6+ Rb4[Te3 Te 5 O23](#703) has a defect pyrochlore (Na1.6Ag0.4)[Te2 Te 3 O14](#702). However, tewite superstructure. Intact kagome layers of mixed Te4+ contains only Te4+. It cannot be placed more precisely and Te6+ polyhedra occur || (220) and (220) of the in our classification without knowledge of the orthorhombic cell. However, there are also modi- coordination environment of the Te atoms.  4+ 6+ fied kagome layers || (201) and (201), with some Kuranakhite, PbMn (Te O6), is a long-known oxygen atoms missing so as to allow reduction of mineral (Yablokova et al., 1975) whose structure the Te4+ coordination number from 6 to 5, and to has never been fully determined. However, its unit provide space for accommodation of the stereo- cell parameters suggest that it is structurally related + 4+ active lone pairs (Fig. 16h). CN8–10 Rb ions to the Li2[M (TeO6)] phases #583–585, based occupy the large interstices in the framework. upon a hcp array of oxygen atoms, but with one Pb2+ replacing two Li+ ions. Grundler et al. (2008) suggested that the hydrated Ca analogue xocolatlite Additional tellurium oxyminerals was structurally related to kuranakhite, which seems feasible. Cheremnykhite, Pb3[Zn3(TeO6) In the section above on zemannite and related (VO4)2], was noted earlier as probably isotypical compounds (#131‒136), we mentioned the minerals with dugganite and kuksite (#550–551), on the kinichilite, keystoneite and ilirneyite as isostructural basis of its stoichiometry and unit-cell dimensions. with zemannite itself, although their crystal structures However, although it has a strongly pseudo- have not been published. For completeness, the hexagonal unit-cell metric with b = √3a, note that available data on these species are included in its symmetry is reported as orthorhombic, Cmmm, Table 27, along with several other minerals for Cmm2, Cm2m or C222. None of these can be which refinements are not yet available, but for which correct if the symmetry is a subgroup of the P321 some structural details can be deduced. Such species space group exhibited by #550–551. Such a could not be included in the classification above, as relationship would imply that cheremnykhite is quantitative bond-distance data are not available. actually monoclinic C211, with α ≈ 90°. 4+ 6+ Millsite, Cu(Te O3)·2H2O(Rumseyet al., Andychristyite, Pb2[Cu2(Te2 O10)] · 2H2O (Kampf 2016), is a new dimorph of teineite (#119)witha et al., 2016), is a new mineral that is chemically the 2– unique structure in which TeO3 pyramids Pb analogue of eckhardite (#639). However, cross-link Cu2O2(H2O)4 dimers to form a although the structures of the two minerals are two-dimensional layer. Telluromandarinoite related, they are not the same. Both contain

520 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

8– edge-sharing [Te2O10] dimers, and both have Allmann, R. (1976) Te(OH)6 · NaF, eine Struktur mit structure units based upon stepped oblique slices kurzen OH···F-Wasserstoffbrücken. Acta through a hcp anion array (cf. #512–515), but the Crystallographica, B32, 1025–1028. component ribbons of the slices and disposition of Allmann, R. and Haase, W. (1976) Crystal structure of an the Te=Te dimers are different. adduct of with potassium fluoride, There remain several Te minerals for which Te(OH)6 · 2KF. A compound with short oxygen- structures have never been determined, and even hydrogen··· hydrogen bonds. Inorganic 15 – the true valence state of Te remains unknown. This is Chemistry, , 804 807. the case even for apparently simple species such as Almond, P.M. and Albrecht Schmitt, T.E. (2002) Expanding , Cu (Te4+O ) (OH) ·2H O (Williams, the remarkable structural diversity of uranyl tellurites: 5 3 2 6 2 hydrothermal preparation and structures of 1974) and xocometatlite, Cu Te 6+ O (OH) 3 4 4 K(UO Te O (OH)), Tl ((UO ) (Te O (OH))(Te O )) · (Williams, 1975). As these minerals become better 2 2 5 3 2 2 2 5 2 6 2(H O), β-Tl (UO (TeO ) )andSr(UO (TeO ) ) characterized and additional natural and synthetic Te 2 2 2 3 2 3 2 3 2 (TeO3)2. Inorganic Chemistry, 41,5495–5501. oxycompounds are discovered, the diversity of Almond, P.M., McKee, M.L. and Albrecht Schmitt, T.E. known structures is likely to increase. However, (2002) Unusual uranyl tellurites containing the dataset and classification of the present study are 4– (Te2O6) ions and three-dimensional networks. sufficiently large to provide a robust framework into Angewandte Chemie, International Edition, 41, which new structural architectures can be fitted. 3426–3429. Alonso, J.A., Castro, A., Enjalbert, R., Galy, J. and Rasines, I. (1992) The quadruple chains of SbO6 Acknowledgements octahedra in Sb2Te 2O9: an example of low extent of aggregation of pentavalent polyhedra. We thank Mark Welch and Sergey Krivovichev for Dalton Transactions, 17, 2551–2557. their helpful comments on the manuscript and Helen An, Y., Mosbah, A., Le Gal La Salle, A., Guyomard, D., Kerbey for all her help with setting up the article for Verbaere, A. and Piffard, Y. (2001) K2[Te4O8(OH)10]: publication. This study has been funded by The Ian synthesis, crystal structure and thermal behavior. Solid Potter Foundation grant “tracking tellurium” to SJM State Sciences, 3,93–101. which is gratefully acknowledged. Anders, E. and Ebihara, M. (1982) Solar system abundances of the elements. Geochimica et Cosmochimica Acta, 46, 2363–2380. References Andersen, L. and Moret, J. (1983) Dipotassium ditellur- ium (IV) pentaoxide trihydrate, K2Te 2O5 ·3H2O. Acta Abdelhedi, M., Dammak, M., Cousson, A. and Kolsi, A. Crystallographica, C39, 143–145. W. (2005) Structural, calorimetric and conductivity Andersen, L., Lindqvist, O. and Moret, J. (1984) The study of the new mixed solution structures of tellurate (IV) hexahydrate, Rb2(SO4)0.5(SeO4)0.5Te(OH)6. Journal of Alloys and MgTeO3 ·6H2O, and magnesium selenate (IV) hex- 398 – Compounds, ,55 61. ahydrate, MgSeO3 ·6H2O. Acta Crystallographica, Ahmed, M.A., Fjellvåg, H. and Kjekshus, A. (2000) C40, 586–589. Synthesis, structure and thermal stability of tellurium Andersen, L., Langer, V., Stromberg, A. and Stromberg, oxides and sulfate formed from reactions in refluxing D. (1989) The structure of K2TeO 3 – an experimental . Dalton Transactions, 24, 4542–4549. and theoretical study. Acta Crystallographica, B45, Ajaz, H., Deiseroth, H.J., Schlosser, M. and Rabbani, F. 344–348. (2009) Synthesis and crystal structure of Anderson, J.B., Rapposch, M.H., Anderson, C.P. and tellurium trioxide bromide. Synthesis and Reactivity Kostiner, E. (1980) Crystal structure refinement of basic + − in Inorganic, Metal-Organic, and Nano-Metal tellurium nitrate: A reformulation as (Te2O4H) (NO3) . Chemistry, 39, 209–210. Monatshefte für Chemie/Chemical Monthly, 111, Al Ansari, S.V.,Al Ansari, Ya.F., Chumakov, V.M., Albov, 789–796. D.V., Savinkina, E.V., Davydova, M.N. and Tsivadze, Anderson, J.S. (1937) Constitution of the poly-acids. A.Y. (2007) Synthesis and structure of the stoichio- Nature, 140, 850. metric sodium bis(dihydrotellurato)cuprate(III) Andersson, S. (1978) Structures related to the β-tungsten 52 Na5[Cu(H2TeO 6)2] · 16(H2O). Kristallografiya, , or Cr3Si structure type. Journal of Solid State 256–258. Chemistry, 23, 191–204. Alcock, N.W. and Harrison, W.D. (1982) Refinement of Andrade, M.B., Yang, H., Downs, R.T., Jenkins, R.A. the structure of tellurium phosphate Te2O3 ·HPO4. and Fay, I. (2014) Te-rich raspite, Pb(W0.56Te 0.44)O4, Acta Crystallographica, B38, 1809–1811. from Tombstone, , U.S.A: the first natural

521 A. G. CHRISTY ET AL.

example of Te6+ substitution for W6+. American compose d’addition urée-acide tellurique: Te Mineralogist, 99, 1507–1510. (OH)6(CO(NH2)2)2. Comptes Rendus Andreae, M.O. (1984) Determination of inorganic Hebdomadaires des Séances de l’Academie des tellurium species in natural waters. Analytical Sciences, Serie C, 309,25–28. Chemistry, 56, 2064–2066. Averbuch-Pouchot, M.T. and Durif, A. (1990) Crystal Arnaud, Y., Averbuch-Pouchot, M.T., Durif, A. and chemistry of cyclo-hexaphosphates. VI. Structure of Guidot, J. (1976) Structure cristalline de l’oxyde ammonium cyclo-hexaphosphate tellurate dihydrate. ̀ C46 – mixte de molybdene-tellure: MoTe2O7. Acta Acta Crystallographica, , 179 181. Crystallographica, B32, 1417–1420. Averbuch-Pouchot, M.T. and Durif, A. (1991) Crystal Artner, C. and Weil, M. (2012) Pb6Co9(TeO6)5. Acta chemistry of cyclo-hexaphosphates. XVI. Structures Crystallographica, E68, i71–i71. of potassium cyclo-hexaphosphate ditellurate tri- Artner, C. and Weil, M. (2013) Re-examination of Pb3TeO 6: hydrate and rubidium cyclo-hexaphosphate tritellurate C47 – Determination of its correct composition as Pb5TeO 8. tetrahydrate. Acta Crystallographica, ,1576 1579. Journal of Solid State Chemistry, 199, 240–247. Averbuch-Pouchot, M.T. and Durif, A. (1992) Structure of Astier, R., Philippot, E., Moret, J. and Maurin, M. (1979) an adduct between diammonium dihydrogendi- Evolution de la coordination des atomes de tellure IV phoshate and telluric acid: (NH4)2H2P2O7 · Te(OH)6. ̀ C48 – et de fer III dans les composés du systeme Fe2O3– Acta Crystallographica, , 973 975. 13 – TeO 2. Revue de Chimie Minerale, , 359 372. Averbuch-Pouchot, M.T. and Durif, A. (1993a) Augsburger, M.S., Viola, M.C., Pedregosa, J.C., Munoz, Ammonium cyclo-octaphosphate-telluric acid dihy- A., Alonso, J.A. and Carbonio, R.E. (2005) drate adduct. Acta Crystallographica, C49, 361–363. Preparation, crystal and magnetic structures of two Averbuch-Pouchot, M.T. and Durif, A. (1993b) new double perovskites: Ca2CoTeO6 and Sr2CoTeO6. Cs2H2P2O7 · Te(OH)6, a new adduct between a Journal of Materials Chemistry, 15, 993–1001. diphosphate and telluric acid. European Journal of Averbuch-Pouchot, M.T. (1980) Structure d’un phosphate Solid State Inorganic Chemistry, 30, 1153–1162. tellurate de sodium: Te(OH)6 ·Na2HPO4 · NaH2PO4. Averbuch-Pouchot, M.T. and Schuelke, U. (1996) Acta Crystallographica, B36, 2405–2406. Preparation and crystal structure of guanidinium cyclo- Averbuch-Pouchot, M.T. (1983) Crystal chemistry of some dodecaphosphate telluric acid hydrate: (C addition compounds of alkali iodates with telluric acid. (NH2)2)12P12O36 · 12Te(OH)6. 24H2O. Zeitschrift für Journal of Solid State Chemistry, 49,368–378. anorganische und allgemeine Chemie, 622, 1997–2002. Averbuch-Pouchot, M.T. (1984) Crystal structure of Te Averbuch-Pouchot, M.T.,Durif, A. and Guitel, J.C. (1979) ’ (OH)6 · 2KNO3 ·2H2O: an addition compound of tel- Structure cristalline d un phospho-tellurate de rubid- luric acid. Zeitschrift für Kristallographie, 167,247–252. ium: Te(OH)6Rb2(HPO4)Rb(H2PO4). Materials Averbuch-Pouchot, M.T. (1988a) Structure of a new Research Bulletin, 14, 1219–1223. adduct between telluric acid and a condensed Averbuch-Pouchot, M.T., Durif, A. and Guitel, J.C. (1980) phosphate: Cs3P3O9 · Te(OH)6 ·H2O. Acta Crystal structures of two cesium phosphate-tellurates: (Te Crystallographica, C44, 1166–1168. (OH)6)(Cs2HPO4) and (Te(OH)6)(Cs2HPO4) Averbuch-Pouchot, M.T. (1988b) Crystal structure of a (CsH2PO4)2. Materials Research Bulletin, 15, 387–395. new telluric acid adduct: Te(OH)6 · 2CsCl. Zeitschrift Ayed, B. and Haddad, A. (2013) The crystal structure of für Kristallographie, 182, 291–295. potassium ammonium hexamolybdotellurate with Averbuch-Pouchot, M.T. and Durif, A. (1981) Crystal data telluric acid K5NH4(TeMo6O24) · Te(OH)6 ·6H2O. 16 – for two new phosphate-tellurates: Te(OH)6(Tl Comptes Rendus Chimie, ,114 121. (H2PO4))2(Tl2(HPO4)) and Te(OH)6(Tl(H2PO4))2. Babel, D. (1967) Structural chemistry of octahedral Materials Research Bulletin, 16,71–76. fluorocomplexes of the transition elements. Structure Averbuch-Pouchot, M.T. and Durif, A. (1983) Structure of and Bonding, 3,1–87. a potassium diphosphate tellurate hydrate, K3HP2O7 · Back, M.E., Grice, J.D., Gault, R.A., Criddle, A.J. and Te(OH)6 ·H2O. Acta Crystallographica, C39,27–28. Mandarino, J.A. (1999) Walfordite, a new tellurite Averbuch-Pouchot, M.T. and Durif, A. (1987a) Structure species from the Wendy open pit, El Indio-Tambo of a new adduct between telluric acid and a condensed mining property, Chile. The Canadian Mineralogist, 37 – phosphate: K4P4O12 · Te(OH)6 ·2H2O. Acta , 1261 1268. Crystallographica, C43, 1245–1247. Back, M.E., Grice, J.D., Sturman, B.D., Cooper, M.A., Averbuch-Pouchot, M.T. and Durif, A. (1987b) Crystal Gault, R.A. and Walford, P.C. (2011) structure of a new adduct between telluric acid and Telluromandarinoite, IMA 2011-013. CNMNC alkali cyclo-triphosphates: Te(OH)6 ·Na3P3O9 · Newsletter No. 10, October 2011, page 2551. 75 – K3P3O9. Acta Crystallographica, C43, 1653–1655. Mineralogical Magazine, , 2549 2561. Averbuch-Pouchot, M.T. and Durif, A. (1989) Baker, L.C.W. and Figgis, J.S. (1970) A new fundamental Determination des liaisons hydrogenè dans le type of inorganic complex: hybrid between the

522 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

heteropoly and conventional coordination complexes. Becker, R. and Johnsson, M. (2007) Three new tellurite Possibilities for geometrical isomerism in 11-, 12-, 17- halides with unusual Te4+ coordinations and and 18-heteropoly derivatives. Journal of the honeycomb lattice variants. Journal of Solid State American Chemical Society, 92, 3794–3797. Chemistry, 180, 1750–1758. Baldinozzi, G., Grebille, D., Sciau, P., Kiat, J.M., Moret, J. Becker, R. and Mats, J. (2005) Crystal structure of Cu3Bi and Berar, J.F. (1998) Rietveld refinement of the (TeO3)2O2Cl: a Kagome lattice type compound. Solid incommensurate structure of the elpasolite (ordered State Sciences, 7, 375–380. perovskite) Pb2MgTeO6. Journal of Physics: Becker, C.R., Tagg, S.L., Huffman, J.C. and Zwanziger, J. Condensed Matter, 10, 6461–6472. W.(1997) Crystal structures of potassium tetratellurite, Balraj, V. and Vidyasagar, K. (1998) Low-temperature K2Te 4O9, and potassium ditellurite, K2Te 2O5, and syntheses and characterization of novel layered tell- structural trends in solid alkali tellurites. Inorganic “ 36 – urites, A2Mo3TeO 12 (A =NH4, Cs), and zero- Chemistry, , 5559 5564. dimensional” tellurites, A4Mo6Te 2O24 ·6H2O(A = Becker, R., Johnsson, M., Kremer, R. and Lemmens, P. Rb, K). Inorganic chemistry, 37, 4764–4774. (2003) Crystal structure, magnetic properties and Balraj,V.andVidyasagar,K.(1999a) Hydrothermal synthesis conductivity of CuSbTeO3Cl2. Solid State Sciences, and characterization of novel one-dimensional tellurites of 5, 1411–1416. (VI), A4Mo6TeO 22 ·2H2O(A =NH4,Rb). Becker, R., Johnsson, M., Kremer, R. and Lemmens, P. Inorganic Chemistry, 38,1394–1400. (2005) Crystal structure and magnetic properties of Balraj, V. and Vidyasagar, K. (1999b) Hydrothermal Cu3(TeO3)2Br2 – a layered compound with a new Cu synthesis and characterization of a novel two-dimen- (II) coordination polyhedron. Journal of Solid State sional tellurite of molybdenum (VI), Chemistry, 178, 2024–2029. 38 (NH4)6Mo8Te 8O43(H2O). Inorganic Chemistry, , Becker, R., Berger, H., Johnsson, M., Prester, M., 3458–3462. Morohnic, Z., Miljak, M. and Herak, R. (2006a) Balraj, V. and Vidyasagar, K. (1999c) Syntheses and Crystal structure and magnetic properties of characterization of novel three-dimensional tellurites, Co2TeO 3Cl2 and Co2TeO 3Br2. Journal of Solid State Na2MTe 4O12 (M = W, Mo), with intersecting tunnels. Chemistry, 179, 836–842. Inorganic Chemistry, 38, 5809–5813. Becker, R., Johnsson, M., Berger, H., Prester, M., Bartram, S.F.(1966) Crystal structure of the rhombohedral Zivkovic, I., Drobac, D., Miljak, M. and Herak, R. MO3 ·3R2O3 compounds (M = U, W or Mo) and their (2006b) Crystal structure and magnetic properties of relation to ordered R7O12 phases. Inorganic Co7(TeO3)4Br6 – a new cobalt tellurite bromide. Solid Chemistry, 5, 749–754. State Sciences, 8, 836–842. Basciano, L.C., Peterson, R.T., Roeder, P.L. and Becker, R., Prester, M., Berger, H., Johnsson, M., Drobac, Swainson, I. (1998) Description of schoenfliesite, D. and Zivkovic, I. (2007a) Crystal structure and MgSn(OH)6, and roxbyite, Cu1.72S, from a 1375 BC magnetic properties of the new cobalt tellurite halide 9 shipwreck, and Rietveld neutron-diffraction refine- Co5(TeO3)4X2 (X = Cl, Br). Solid State Sciences, , ment of synthetic schoenfliesite, wickmanite MnSn 223–230. (OH)6 and burtite, CaSn(OH)6. The Canadian Becker, R., Johnsson, M. and Berger, H. (2007b) Crystal Mineralogist, 36, 1203–1210. structure of the new cobalt tellurite chloride Basso, R., Lucchetti, G., Zefiro, L. and Palenzona, A. Co5Te 4O11Cl4. Zeitschrift für anorganische und 633 – (1996) Rosiaite, PbSb2O6, a new mineral from the allgemeine Chemie, , 422 424. Cetine mine, Siena, Italy. European Journal of Benmiloud, L., Moret, J., Maurin, M. and Philippot, E. Mineralogy, 8, 487–492. (1980) Structure d’un tellurate d’ammonium: Bats, J.W. (1978) A refinement of potassium chlorate. NH4TeO3(OH). Acta Crystallographica, B36,139–141. Acta Crystallographica, B34, 1679–1681. Benmiloud, L., Maurin, M., Moret, J. and Philippot, E. Bazuev, G.V., Golovkin, G.V., Zubkov, V.G. and (1981) Étude cristallographique d’un tellurite d’am- Tyutyunnik, A.S. (1994) Synthesis, crystal structure, monium: (NH4)2Te 4O9. Revue de Chimie Minerale, and magnetic properties of complex oxides Cu2BSbO6 18, 190–198. (B = Mn,Fe,Ga) with a bixbyite structure. Journal of Berand, N. and Range, K.J. (1994) Single-crystal Solid State Chemistry, 113, 132–137. structure refinement of the trirutile-type compound 205 Becker, R. and Berger, H. (2006a) Reinvestigation of Ga2TeO 6. Journal of Alloys and Compounds, , Ni3TeO 6. Acta Crystallographica, E62, i222–i223. 3–5. Becker, R. and Berger, H. (2006b)Cu2CoTeO6. Acta Berdonosov, P.S., Dolgikh, V.A. and Lightfoot, P. (2007) Crystallographica, E62, i261–i262. The crystal structure of a new tellurium Becker, R. and Johnsson, M. (2004) Crystal structure of oyxchloride Bi0.87Te 2O4.9Cl0.87 from neutron powder the new compound Co6(TeO3)2(TeO6)Cl2. Solid State diffraction data. Journal of Solid State Chemistry, 180, Sciences, 6, 519–522. 1533–1537.

523 A. G. CHRISTY ET AL.

Berger, S.V.(1988) The crystal structure of the isomorph- Boukharrata, N.J., Duclere,̀ J.-R, Laval, J.P. and Thomas, ous orthoborates of cobalt and magnesium. Acta P. (2013) A new oxyfluorotellurate(IV), InTe2O5F. Chemica Scandinavica, 3, 660–675. Acta Crystallographica, C69, 460–462. Beyer, H. (1967) Verfeinerung der Kristallstruktur von Bragg, W.L. (1930) The structure of silicates. Zeitschrift Tellurit, dem rhombischen TeO2. Zeitschrift für fur Kristallographie, 74, 237–305. Kristallographie, 124, 228–237. Brandstätter, F. (1981) Synthesis and crystal structure Bhuvanesh, N.S.P. and Halasyamani, P.S. (2001) determination, of Pb2[UO2][TeO3]3. Zeitschrift für Synthesis and characterization of NaGaTe2O6 · 2.4 Kristallographie, 155, 193–200. (H2O): a new open-framework tellurite related to Brandt, B.G. and Skapski, A.C. (1967) A refinemnt of the zemannite. Inorganic Chemistry, 40, 1404–1405. crystal structure of molybdenum dioxide. Acta Bindi, L. and Cipriani, C. (2003) The crystal structure of Chemica Scandinavica, 21, 661–672. winstanleyite, TiTe3O8, from the Grand Central Mine, Brese, N.E. and O’Keeffe, M. (1991) Bond-valence Tombstone, Arizona. The Canadian Mineralogist, 41, parameters for solids. Acta Crystallographica, B47, 1469–1473. 192–197. Bindi, L. and Pratesi, G. (2007) Centric or acentric crystal Brown, I.D. (1969) Crystal structures of NaNiIO6, structure for natural schmitterite, UTeO5?New NaMnIO6, and KMnIO6. Canadian Journal of evidence from a crystal from the type locality. Chemistry, 47, 3779–3782. Mineralogy and Petrology, 91, 129–138. Brown, I.D. (2002) The Chemical Bond in Inorganic Blanchandin, S., Champarnaud-Mesjard, J.C., Thomas, P. Chemistry: The Bond Valence Model. Oxford and Frit, B. (2000a) Crystal structure of BiNbTe2O8. University Press, UK, 278 pp. Solid State Sciences, 2, 223–228. Brown, I.D. and Altermatt (1985) Bond-valence Blanchandin, S., Champarnaud-Mesjard, J.C., Thomas, P. parameters obtained from a systematic analysis of and Frit, B. (2000b) Crystal structure of Nb2Te 4O13. the Inorganic Crystal Structure Database. Acta Journal of Alloys and Compounds, 306, 175–185. Crystallographica, B41, 244–247. Boher, P., Garnier, P., Gavarri, J.R. and Hewat, A.W. Brunton, G. (1973) Li2ZrF6. Acta Crystallographica, (1985) Monoxyde quadratique PbOα(I): description B29, 2294–2296. de la transition structurale ferroélastique. Journal of Burckhardt, H.G., Platte, C. and Trömel, M. (1982) 57 – Solid State Chemistry, , 343 350. Cadmiumorthotellurat (VI) Cd3TeO 6: ein pseudo- Bonaccorsi, E., Merlino, S. and Orlandi, P. (2007) orthorhombischer Kryolith im Vergleich mit Zincalstibite, a new mineral, and cualstibite: crystal Ca3TeO 6. Acta Crystallographica, B38, 2450–2452. chemical and structural relationships. American Burdett, J.K. and McLarnan, T.J. (1984) An orbital Mineralogist, 92, 198–203. interpretation of Pauling’s rules. American Boren, B. (1933) X-ray investigation of alloys of silicon Mineralogist, 69, 601–621. with , , cobalt and . Arkiv Burns, P.C., Cooper, M.A. and Hawthorne, F.C. (1995) 11A – 2+ 6+ för Kemi, Mineralogi och Geologi, ,2 10. Parakhinite, Cu3 PbTe O6(OH)2; crystal structure Bouchama, M. and Tournoux, M. (1975) Polytypisme de and revision of . The Canadian TlSbO3. Revue de Chimie Minérale, 12,80–92. Mineralogist, 33,33–40. Boudjada, N. and Durif, A. (1982) Structure d’un Burns, P.C.,Ewing, R.C. and Hawthorne, F.C. (1997) The trimetaphosphate-tellurate de rubidium monohydrate: crystal chemistry of hexavalent : polyhedron Te(OH)6 ·Rb3P3O9 ·H2O. Acta Crystallographica, geometries, bond-valence parameters, and polymer- B38, 595–597. ization of polyhedra. The Canadian Mineralogist, 35, Boudjada, N., Averbuch-Pouchot, M.T. and Durif, A. 1551–1570. (1981a) Structure du trimetaphosphate-tellurate de Burns, P.C., Pluth, J.J., Smith, J.V., Eng, P., Steele, I. and sodium hexahydrate Te(OH)6 · (Na3P3O9)2 ·(H2O)6. Housley, R.M. (2000) Quetzalcoatlite: A new octahe- Acta Crystallographica, B37, 645–647. dral-tetrahedral structure from a 2 × 2 × 40 μm3 crystal Boudjada, N., Averbuch-Pouchot, M.T. and Durif, A. at the Advanced Photon Source-GSE-CARS Facility. (1981b) Structure d’un trimetaphosphate-tellurate de American Mineralogist, 85, 604–607. potassium dihydrate Te(OH)6 ·K3P3O9 ·2H2O. Acta Byström, A., Hok, B. and Mason, B. (1942) The crystal Crystallographica, B37, 647–649. structure of metantimonate and similar com- Boujada, N., Boujada, A. and Guitel, J.C. (1983) pounds. Arkiv för Kemi, Mineralogi och Geologi, Hexaammonium cyclo-triphosphate telluric acid. 154B4,1–8. Acta Crystallographica, C39, 656–658. Cachau-Herreillat, D., Norbert, A., Maurin, M. and Boukharrata, N.J., Thomas, P. and Laval, J.P. (2009) Philippot, E. (1981) Étude cristallochimique comparée GeTe2O6, a tellurate(IV) with an open et conductivité ionique des deux variétés Li2Te 2O5 α et framework. Acta Crystallographica, C65, i23–i26. β. Journal of Solid State Chemistry, 37,352–361.

524 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

Cachau-Herreillat, D., Norbert, A., Maurin, M., Fourcade, binary compounds and carbonate. Acta R. and Philippot, E. (1983) Synthese,̀ étude structurale Crystallographica, B49, 987–996. par rayons X et par spectrometrie infrarouge et Raman Christy, A.G. (2015) Causes of anomalous mineralogical du tellurite basique Li2TeO 3, LiOH. Revue de Chimie diversity in the Periodic Table. Mineralogical Minerale, 20, 129–139. Magazine, 79,33–49. Carbone, C., Basso, R., Cabella, R., Martinelli, A., Grice, Christy, A.G. and Mills, S.J. (2013) Effect of lone-pair J.D. and Lucchetti, G. (2013) Mcalpineite from the stereoactivity on polyhedral volume and structural IV Gambatesa mine, Italy, and redefinition of the species. flexibility: application to Te O6 octahedra. Acta American Mineralogist, 98, 1899–1905. Crystallographica, B69, 446–456. Chabchoub, N., Darriet, J. and Khemakhem, H. (2006) Christy, A.G., Kampf, A.R., Mills, S.J., Housley, R.M. Structural and conductivity studies of CsKSO4Te and Thorne, B. (2014) Crystal structure and revised 3+ 6+ (OH)6 and Rb1.25K0.75SO4Te(OH)6 materials. chemical formula for burckhardtite, Pb2(Fe Te ) Journal of Solid State Chemistry, 179, 2164–2173. [AlSi3O8]O6: a double-sheet silicate with intercalated Champarnaud-Mesjard, J.C., Blanchandin, S., Thomas, phyllotellurate layers. Mineralogical Magazine, 78, P., Mirgorodsky, A., Merle-Mejean, T. and Frit, B. 1763–1773. (2000) Crystal structure, Raman spectrum and lattice Christy, A.G., Mills, S.J., Kampf, A.R., Housley, R.M., dynamics of a new metastable form of tellurium Thorne, B. and Marty, J. (2016) The relationship dioxide: γ-TeO2. Journal of Physics and Chemistry of between mineral composition, crystal structure and Solids, 61, 1499–1507. paragenetic sequence: the case of secondary Te Champarnaud-Mesjard, J.C., Frit, B., Chagraoui, A. and mineralization at the Bird Nest drift, Otto Mountain, Taïri, A. (1996a) New anion-excess, fluorite-related, California, USA. Mineralogical Magazine, 80, – ordered structure: Bi2Te 2W3O16. Journal of Solid 291 310. State Chemistry, 127, 248–255. Churakov, A.V., Ustinova, E.A., Prikhodchenko, P.V., Champarnaud-Mesjard, J.C., Frit, B., Chagraoui, A. and Tripol’skaya, T.A. and Howard, J.A.K. (2007) Taïri, A. (1996b) Crystal structure of a new cation- Synthesis and crystal structure of new alkali metal ordered fluorite-related phase: Bi2Te 2WO10. hydrogen tellurates. Zhurnal Neorganicheskoi Khimii, Zeitschrift für anorganische und allgemeine Chemie, 52, 1605–1612. 622, 1907–1912. Ciobanu, C.L., Cook, N.J. and Spry, P.G.(2006) Preface – Charushnikova, I.A., Yusov, A.B., Fedoseev, A.M. and Special Issue: telluride and selenide minerals in gold Polyakova, I.N. (2004) F-element complexes with deposits–how and why? Mineralogy and Petrology, tellurometallate anions: I. The crystal structure of 87, 163–169. Eu2TeMo6O24 · 18(H2O). Zhurnal Neorganicheskoi Cohen-Addad, C. (1977) Étude structurale des hydro- Khimii, 49, 1481–1487. xystannates CaSn(OH)6 et ZnSn(OH)6 par diffraction Charushnikova, I.A., Fedoseev, A.M., Yusov, A.B. and neutronique, absorption infrarouge et résonance Auwer, C.D. (2005) Crystal structure of a new magnétique nucléaire. Bullétin de la Société hexamolybdotellurate, Nd2TeMo6O24 · Française de Minéralogie et de Cristallographie, 91, 19H2O. Kristallografiya, 52, 223–225. 315–324. Chi, E.O., Ok, K.M., Porter, Y. and Halasyamani, P.S. Colville, A.A., Anderson, C.P. and Black, P.M. (1971) (2006) Na2Te 3Mo3O16: A new molybdenum tellurite Refinement of the crystal structure of apophyllite: I. with second-harmonic generating and pyroelectric X-ray diffraction and physical properties. American properties. Chemistry of Materials, 18, 2070–2074. Mineralogist, 56, 1222–1233. Choisnet, J., Bizo, L., Allix, M., Rosseinsky, M.J. and Cook, N.J. and Ciobanu, C.L. (2005) Tellurides in Au Raveau, B. (2007) Cation ordering in the fluorite-like deposits: implications for modelling. Pp. 1387–1390 transparent conductors In4+xSn3–2xSbxO12 and In6TeO 12. in: Mineral Deposit Research: Meeting the Global Journal of Solid State Chemistry, 180, 1002–1010. Challenge (J.W. Mao and F.P. Bierlein, editors). Choisnet, J., Rulmont, A. and Tarte, P. (1988) Les Springer, Berlin Heidelberg New York. tellurates mixtes Li2ZrTeO6 et Li2HfTeO6:un Cooper, M.A. and Hawthorne, F.C. (1996) The crystal nouveau phenomenè d’ordre dans la famille corindon. structure of spiroffite. The Canadian Mineralogist, 34, Journal of Solid State Chemistry, 75, 124–135. 821–826. Choisnet, J., Rulmont, A. and Tarte, P. (1989) Ordering Cooper, M.A., Hawthorne, F.C. and Back, M.E. (2008) phenomena in the LiSbO3 type structure: The new The crystal structure of khinite and polytypism in mixed tellurates Li2TiTeO6 and Li2SnTeO6. Journal of khinite and parakhinite. Mineralogical Magazine, 72, Solid State Chemistry, 82, 272–278. 763–770. Christy, A.G. (1993) Multistage diffusionless pathways Coppens, P. and Eibschütz, M. (1965) Determination of for reconstructive phase transitions: application to the crystal structure of orthoferrite and

525 A. G. CHRISTY ET AL.

refinement of the structure of orthoferrite. Daniel, F., Moret, J., Maurin, M. and Philippot, E. (1982) Acta Crystallographica, 19, 524–531. Étude du tellurite mixte de sodium et de potassium à Corella-Ochoa, M.N., Miras, H.N., Kidd, A., Long, D.L. trois molecules d’eau: NaKTeO2 ·3H2O. Acta and Cronin, L. (2011) Assembly of a family of mixed Crystallographica, B38, 703–706. 2– metal (Mo:V) polyoxometalates templated by (TeO3) : Daniel, P., Bulou, A., Rousseau, M., Nouet, J., Fourquet, (Mo12V12Te 3), (Mo12V12Te 2) and (Mo17V8Te). J.L., Leblanc, M. and Burriel, R. (1990) A study of the Chemical Communications, 47,8799–8801. structural phase transitions in AlF3: X-ray powder Crosnier, M.P., Delarue, E., Choisnet, J. and Fourquet, J. diffraction, DSC and Raman scattering investigations + + L. (1992) Li /H exchange on Li2TiTeO6. European of the lattice dynamics and phonon spectrum. Journal Journal of Solid State and Inorganic Chemistry, 29, of Physics: Condensed Matter, 2, 5663–5677. 321–332. Darriet, J. (1973) Structure cristalline de la phase Dammak, M., Khemakhem, H., Mhiri, T., Kolsi, A.W.and LiVTeO5. Bulletin de la Societe Francaise de Daoud, A. (1998) Structure and characterization of a Mineralogie et de Cristallographie, 96,97–99. mixed crystal Rb2SO4 · Te(OH)6. Journal of Alloys Darriet, J. and Galy, J. (1973) Tellurium (IV) and Compounds, 280, 107–113. (V) oxide, Te2V2O9. Crystal Structure Dammak, M., Khemakhem, H., Mhiri, T., Kolsi, A.W.and Communications, 2, 237–238. Daoud, A. (1999) Structural and vibrational study of Dawson, B. (1953) The structure of the 9(18)-heteropoly K2SeO4 · Te(OH)6 material. Journal of Solid State anion in potassium 9(18)-tungstophosphate, Chemistry, 145, 612–618. K6(P2W18O62) · 14H2O. Acta Crystallographica, 6, Dammak, M., Mhiri, T., Jaud, J. and Savariault, J.M. 113–126. (2001) Structural study of the two new cesium sulfate Deer, W.A., Howie, R.A. and Zussman, J. (1966) An and selenate tellurate Cs2SO4.Te(OH)6 and Cs2SeO4. Introduction to the Rock-Forming Minerals. Te(OH)6. International Journal of Inorganic Longman, London, 528 pp. Materials, 3, 861–873. Delage, C., Carpy, A. and Goursolle, M. (1982) The Dammak, M., Ktari, L., Cousson, A. and Mhiri, T. (2005) TeO 2–SeO2 system. Crystal structure of Te2Se2O8. Structural and conductivity study of a new protonic Comptes Rendus Hebdomadaires des Séances de ’ 295 – conductor Cs0.86(NH4)1.14(SO4)(Te(OH)6). Journal of l Academie des Sciences, Serie C, , 981 983. Solid State Chemistry, 178, 2109–2116. Denes, G., Pannetier, J. and Lucas, J. (1980) About SnF2 Dammak, M., Mhiri, T. and Cousson, A. (2006) Neutron stannous fluoride. II. Crystal structure of β- and γ- structural and vibrational studies of dipotassium SnF2. Journal of Solid State Chemistry, 33,1–11. selenate tellurate. Journal of Alloys and Compounds, Dewan, J.C., Edwards, A.J., Jones, G.R. and Young, I.M. 407, 176–181. (1978) Crystal structure of dilead tritellurate(IV). Dammak, M., Litaiem, H., Gravereau, P., Mhiri, T. and Dalton Transactions, 1978, 1528–1532. Kolsi, A.W. (2007) X-ray and electrical conductivity Dityat’yev, O.A., Berdonosov, P.S., Dolgikh, V.A., studies in the rubidium selenate tellurate. Journal of Aldous, D.W. and Lightfoot, P. (2006) On the crystal Alloys and Compounds, 442, 316–319. structures of SrTeO3. Solid State Sciences, 8, 830–835. Daniel, F., Moret, J., Philippot, E. and Maurin, M. (1977a) Djemel, M., Abdelhedi, M., Dammak, M. and Cousson, Étude structurale de Li2TeO 4. Coordination du tellure A. (2010) Synthesis and crystal structure of ̀ VI et du lithium par les atomes d’oxygene. Journal of (Cs3.5Rb0.5)((Se0.85S0.15)O3)2(Te(OH)6)3. X-ray struc- Solid State Chemistry, 22,113–119. ture analysis online, 26,73–74. Daniel, F., Maurin, M., Moret, J. and Philippot, E. (1977b) Djemel, M., Abdelhedi, M., Zouari, N., Dammak, M. and Étude structurale d’un nouveau tellurate alcalin: Kolsi, A.W. (2012) Structural and conductivity studies Na2TeO 4. Évolution de la coordination du tellure of CsK(SO4)0.32(SeO4)0.68Te(OH)6. Journal of Solid (VI) et du cation quand on passe du cation lithium State Chemistry, 196, 267–273. au sodium. Journal of Solid State Chemistry, 22, Doi, Y., Suzuki, R., Hinatsu, Y. and Ohoyama, K. (2009) 385–391. Magnetic and neutron diffraction study on quaternary Daniel, F., Moret, J., Maurin, M. and Philippot, E. (1978) oxides MTeMoO6 (M = Mn and Zn). Journal of Structure cristalline d’un oxotellurate mixte, TeIV et Physics: Condensed Matter, 21 046006-1–046006-6. VI IV VI Te :K2Te Te 3 O12. Pentacoordination du tellure Dolgikh, V.A., Kholodkovskaya, L.N. and Popovkin, B. ’ ̀ (IV) par les atomes d oxygene. Acta A. (1996) Crystal structure of Bi5TeO 8.5Br2: coordin- Crystallographica, B34, 1782–1786. ation of Te(IV) atoms in layer Sillén phases. Zhurnal Daniel, F., Moret, J., Maurin, M. and Philippot, E. (1981) Neorganicheskoi Khimii, 41, 970–975. Étude cristallographique du tellurite de sodium à deux Dollase, W.A. (1965) Reinvestigation of the structure of IV molecules d’eau, Na2Te 2 O5 ·2H2O. Acta low cristobalite. Zeitschrift für Kristallographie, 121, Crystallographica, B37, 1278–1281. 369–377.

526 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

Donnay, G., Stewart, J.M. and Preston, H. (1970) The Tschermaks mineralogische und petrographische 3+ 4+ crystal structure of sonoraite, Fe Te O3(OH) · H2O. Mitteilungen, 24, 287–298. Tschermaks mineralogische und petrographische Effenberger, H. (1986) Die Kristallstrukturen von drei 14 – Mitteilungen, ,27 44. Modifikationen des Cu(SeO3). Zeitschrift für Downs, R.T. and Palmer, D.C. (1994) The pressure Kristallographie, 175,61–72. behavior of α cristobalite. American Mineralogist, 79, Effenberger, H. and Tillmanns, E. (1993) The crystal 9–14. structure of K2{Cu[TeO4(OH)2]} · H2O. Zeitschrift Drewes, D. and Krebs, B. (2005) Synthesis and structure für Kristallographie, 205,41–53. of a novel type of polyoxomolybdate lanthanide Effenberger, H., Zemann, J. and Mayer, H. (1978) complex: ((Ln(H2O)6)2(TeMo6O24)) (Ln = Ho, Yb). Carlfriesite; crystal structure, revision of chemical Zeitschrift für anorganische und allgemeine Chemie, formula, and synthesis. American Mineralogist, 63, 631, 2591–2594. 847–852. Drewes, D., Limanski, E.M. and Krebs, B. (2004a)A Efremov, V.A., Tyulin, A.V. and Trunov, V.K. (1984) The series of novel lanthanide polyoxometalates: conden- structure of a new modification of Nd2WO6. sation of building blocks dependent on the nature of Kristallografiya, 29, 673–676. rare earth cations. Dalton Transactions, 2004, 2087–2091. Einstein, F.W. and Willis, A.C. (1981) Structure of Drewes, D., Limanski, E.M. and Krebs, B. (2004b) The tellurium (IV) pyrosulphate. Acta Crystallographica, 6– Anderson type anion (TeMo6O24) – a multientate B37, 218–220. ligand for trivalent rare earth cations. European Elerman, Y.(1993) Crystal structure of two polymorphous Journal of Inorganic Chemistry, 2004, 4849–4853. types of SrTeO3. Turkish Journal of Physics, 17,465–473. Driess, M., von Haenisch, C. and Merz, K. (1999) The Ercit, T.S., Hawthorne, F.C. and Černý, P. (1992) The first orthotelluric acid polysilylesters: synthesis and crystal structure of alumotantite: its relationship to the crystal structure of ((Me3SiO)8Te 2O2) and structures of simpsonite. The Canadian Mineralogist, ((Me4Si2O2)3Te). Zeitschrift für anorganische und 30, 653–662. allgemeine Chemie, 625, 493–496. Evans, H.T. (1948) The crystal structures of ammonium Drits, V.A., Kashaev, A.A. and Sokolova, G.V. (1975) and potassium molybdotellurates. Journal of the Crystal-structure of cymrite. Kristallografiya, 20, American Chemical Society, 70, 1291–1292. 280–286. Evans, H.T. (1974) The molecular structure of the Dubler, E., Vedani, A. and Oswald, H.R. (1983) New hexamolybdotellurate ion in the crystal complex with structure determination of murdochite, Cu6PbO8. Acta telluric acid (NH4)6[TeMo6O24] · Te(OH)6 ·7H2O. Crystallographica, C39, 1143–1146. Acta Crystallographica, B30, 2095–2100. Durif, A. and Averbuch-Pouchot, M.T. (1981) Crystal Evstigneeva, M.A., Nalbandyan, V.B., Petrenko, A.A., structure of a silver phosphate-tellurate: Te(OH)6 · Medvedev, B.S. and Kataev, A.A. (2011) A new 2Ag2HPO4. Zeitschrift für anorganische und allge- family of fast sodium ion conductors: Na2M2TeO 6 (M meine Chemie, 472, 129–132. = Ni, Co, Zn, Mg). Chemistry of Materials, 23, Durif, A., Averbuch-Pouchot, M.T.and Guitel, J.C. (1979) 1174–1181. Structures de deux phosphotellurates: Te(OH)6 · Falck, L. and Lindqvist, O. (1978) X-ray refinement of the 2(NH4)2HPO4 et Te(OH)6 ·Na2HPO4 ·H2O. Acta structure of cubic telluric acid. Acta Crystallographica, B 35,1444–1447. Crystallographica, B34, 3145–3146. Durif, A., Averbuch-Pouchot, M.T.and Guitel, J.C. (1982) Falck, L., Lindqvist, O. and Mark, W.(1978a) Tricopper(II) (NH4)4P4O12 · 2Te(OH)6 ·2H2O, the first example of tellurate(VI). Acta Crystallographica, B34, 896–897. a tetrametaphosphate-tellurate. Journal of Solid State Falck, L., Lindqvist, O., Mark, W., Philippot, E. and Chemistry, 41, 153–159. Moret, J. (1978b) The crystal structure of CuTeO4. Dušek, M. and Loub, J. (1988) X-ray powder diffraction Acta Crystallographica, B34, 1450–1453. data and structure refinement of TeO3. Powder Feger, C.R. and Kolis, J.W. (1998a)Na3Mn4Te 2O12. Acta Diffraction, 3, 175–176. Crystallographica, C54, 1055–1057. Dutreilh, M., Thomas, P., Champarnaud-Mesjard, J.C. Feger, C.R. and Kolis, J.W. (1998b)V2MnTeO7. Acta and Frit, B. (2001) Crystal structure of a new Crystallographica, C54, 1217–1219. tellurite: Ga2Te 4O11. Solid State Sciences, 3, Feger, C.R. and Kolis, J.W. (1998c) Synthesis and 423–431. characterization of two new copper tellurites, Dytyatyev, O.A. and Dolgikh, V.A. (1999) On the crystal Ba2Cu4Te 4O11Cl4 and BaCu2Te 2O6Cl2, in super- structure of a new binary oxide Sr3Te 4O11. Materials critical H2O. Inorganic Chemistry, 37, 4046–4051. Research Bulletin, 34, 733–740. Feger, C.R., Schimek, G.L. and Kolis, J.W. (1999) Effenberger, H. (1977) Verfeinerung der Kristallstruktur Hydrothermal synthesis and characterization of von synthetischem Teineit, CuTeO3 ·2H2O. M2Te 3O8 (M = Mn, Co, Ni, Cu, Zn): a series

527 A. G. CHRISTY ET AL.

of compounds with the spiroffite structure. Journal of Fu, W.T. and Ijdo, D.J.W. (2008) Chiolite-like Ca5Te 3O14: Solid State Chemistry, 143, 246–253. An X-ray and neutron diffraction study. Journal of Fischer, R. and Pertlik, F. (1975) Verfeinerung der Solid State Chemistry, 181, 1236–1239. Kristallstruktur des Schafarzikits, FeSb2O4. Fu, W.T., Au, Y.S., Akerboom, S. and Ijdo, D.J.W. (2008) Tschermaks mineralogische und petrographische Crystal structures and chemistry of double perovskites 22 – II VI Mitteilungen, , 236 241. Ba2M M′ O6 (M = Ca, Sr, M′ = Te, W, U). Journal of Fischer, R., Pertlik, F. and Zemann, J. (1975) The crystal Solid State Chemistry, 181, 2523–2529. structure of mroseite, CaTeO2(CO3). The Canadian Fuchs, J., Loederich, R. and Pickardt, J. (1982) Struktur Mineralogist, 13, 383–387. und schwingungsspektrum des tetraguanidinium- Fischer, W. and Koch, E. (2006) Symbols and properties ditellurats, [C(NH2)3]4Te 2O6(OH)4. Zeitschrift für of lattice complexes. Pp. 848–872 in: International Naturforschung B, 37, 587–593. Tables for Crystallography, Volume A. Chapter 14.2. Fujita, T., Kawada, I. and Kato, K. (1977) Raspite from International Union for Crystallography. Broken Hill. Acta Crystallographica, B33, 162–164. Fleet, M.E. (1972) The crystal structure of pararammels- Galuskina, I.O., Vapnik, Y., Lazic, B., Armbruster, T., bergite, NiAs2. American Mineralogist, 57,1–9. Murashko, M. and Galuskin, E.V. (2014) Harmunite Folger, F. (1975a) Die Kristallstruktur von Li2TeO 3. CaFe2O4: a new mineral from the Jabel Harmun, West Zeitschrift für anorganische und allgemeine Chemie, Bank, Palestinian Autonomy, Israel. American 411, 103–110. Mineralogist, 99, 965–975.

Folger, F. (1975b) Die Kristallstruktur von BaTeO3. Galy, J. and Lindqvist, O. (1979) The crystal structure of Zeitschrift für anorganische und allgemeine Chemie, Te 3Nb2O11. Journal of Solid State Chemistry, 27, 411,111–117. 279–286. Forestier, P. and Goreaud, M. (1991) Structure cristalline Galy, J. and Meunier, G. (1971) À propos de la cliffordite ̀ – de l’oxyde a valence mixte TeMo5O16 orthorombique. UTe3O8.Lesysteme UO3 TeO 2 à 700°C. Structure Comptes Rendus Hebdomadaires des Seances de cristalline de UTe3O9. Acta Crystallographica, B27, l’Academie des Sciences, Serie 2, 312, 1141–1145. 608–616. Frau, A.F., Kim, J.H. and Halasyamani, P.S. (2008) Gao, B., Liu, S.X., Xie, L.H., Yu, M., Zhang, C.D., Sun, Na3Ga3Te 2O12: Synthesis, single crystal structure C.Y. and Cheng, H.Y. (2006) Hydrothermal assembly and characterization. Solid State Sciences, 10, of (3,6)-connected networks with classical mineral 1263–1268. structures constructed from Anderson-type hetero- Friauf, J.B. (1927) The crystal structures of two polymolybdate and metal cations. Journal of Solid intermetallic compounds. Journal of the American State Chemistry, 179, 1681–1689. Chemical Society, 49, 3107–3114. Gao, B., Liu, S.X., Zhang, C.D., Xie, L.H., Sun, C.Y.and Friese, K., Halasyamani, P.S., Tolkiehn, M. and Yu, M. (2007) Hydrothermal assembly of pyrite- Grzechnik, A. (2011) A high-pressure single-crystal related framework: (NH4)2((Ni(H2O)3)2(TeW6O24)) 60 synchrotron diffraction study of NH4RbTe4O9 ·2H2O: (H2O). Journal of Coordination Chemistry, , – stability of three different TeOx coordination poly- 911 918. hedra. Acta Crystallographica, C67, i45–i49. Gao, J., Yan, J., Beeg, S., Long, D. and Cronin, L. (2012) Frit, B. (1975) Structure crystalline du tellurate d’indium Assembly of molecular "layered" heteropolyoxo- In2TeO 6. Comptes Rendus Hebdomadaires des metalate architectures. Angewandte Chemie Seances de l’Academie des Sciences, Serie C, 281, International Edition, 51, 3373–3376. 769–772. Garavelli, A., Mitolo, D., Pinto, D. and Vurro, F. (2013) Frit, B. and Jaymes, M. (1974) Synthese et étude Lucabindiite, (K,NH4)As4O6(Cl,Br), a new fumarole structurale des tellurates de bismuth. Bulletin de la mineral from the “La Fossa” crater at Vulcano, Aeolian Société Chimique de France, 1974, 402–406. Islands, Italy. American Mineralogist, 98, 470–477. Frit, B. and Mercurio, D. (1980) Structure cristalline de Gaudin, E., Chaminade, J.P., El Abed, A. and Darriet, J. Tl2TeO 3 stéréochimie des éléments Tl(I) et Te(IV). (2001) Indium tellurium trioxide chloride, InTeO3Cl. Revue de Chimie Minérale, 17, 192–201. Acta Crystallographica, C57, 1004–1005. Frit, B., Pressigout, R. and Mercurio, D. (1975) Synthesè Gavarri, J.R. and Weigel, D. (1975) Oxydes de et étude structurale du tellurate(VI) de (III) plomb. I. Structure crystalline du minium, Pb3O4,à Tl2TeO 6. Materials Research Bulletin, 10, température ambiante (293 K). Journal of Solid State 1305–1312. Chemistry, 13, 252–257. Frit, B., Roult, G. and Galy, J. (1983) Cristallochimie de Geller, S. (1967) Crystal chemistry of garnets. Zeitschrift III VI I VI 125 – Tl6 Te O12 et Tl6Te O6E6: un exemple original de für Kristallographie, ,1 47. l’activité stéréochimique de la paire éléctronique 6s2 Geller, S. (1971) Refinement of the crystal structure of (E) du thallium(I). Journal of Solid State Chemistry, cryolithionite, {Na3}[Al2](Li3)F12. American 48, 246–255. Mineralogist, 56,18–23.

528 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

Genkina, E.A. (1992) Accurate definition of LiSbO3 A2TeMo2O6(PO4)2 (A = K, Rb, Tl, Cs). Chemistry of crystal structure. Kristallografiya, 37, 356–358. Materials, 12, 2239–2243. Glazer, A.M. (1972) The classification of tilted octahedra in Haines, J. and Léger, J.M. (1997) X-ray diffraction perovskites. Acta Crystallographica, B28,3384–3392. study of the phase transitions and structural evolution Goodey, J., Broussard, J. and Halasyamani, P.S. (2002) of tin dioxide at high pressure: relationships Synthesis, structure and characterization of a new between structure types and implications for other second-harmonic-generating tellurite: Na2TeW 2O9. rutile-type dioxides. Physical Review, B17, Chemistry of Materials, 14, 3174–3180. 11144–11154. Goodey, J., Ok, K.M., Broussard, J., Hofmann, C., Escobedo, Haines, J., Léger, J.M., Chateau, C. and Pereira, A.S. F.V. and Halasyamani, P.S. (2003) Syntheses, structures (2000) Structural evolution of rutile-type and CaCl2- and second-harmonic generating properties in new type at high pressure. Physics and 27 – quaternary tellurites: A2TeW 3O12 (A =K, Rb or Cs). Chemistry of Minerals, , 575 582. Journal of Solid State Chemistry, 175,3–12. Haley, M.J., Wallwork, S.C., Duffin, B., Logan, N. and Govett, G.J.S. (1983) Rock Geochemistry in Mineral Addison, C.C. (1997) Hexa-μ-nitrato-μ4-oxo- Exploration; Handbook of Exploration Geochemistry. tetraberyllium. Acta Crystallographica, C53, Elsevier, New York, 461 pp. 829–830. Grew, E.S., Locock, A.J., Mills, S.J., Galuskina, I.O., Hanke, K. (1967) Zinktellurit: Kristallstruktur und Galuskin, E.V.and Hålenius, U. (2013) Nomenclature Beziehungen zu einigen Seleniten. of the garnet supergroup. American Mineralogist, 98, Naturwissenschaften, 54, 199–199. 785–811. Hanke, K., Kupcik, V. and Lindqvist, O. (1973) The Grice, J.D. (1989) The crystal structure of magnolite, crystal structure of CuTe2O5. Acta Crystallographica, 1+ 4+ 27 B29 – Hg2 Te O3. The Canadian Mineralogist, , , 963 970. 133–136. Harari, D., Bernier, J.C. and Poix, P.(1972) Contribution a Grice, J.D. and Roberts, A.C. (1995) Frankhawthorneite, l’étude de deux téllurates de type perovskite. Journal a unique HCP framework structure of a cupric of Solid State Chemistry, 5, 382–390. tellurate. The Canadian Mineralogist, 33, 649–654. Harrison, W.T.A. (2014) Crystal structure of ammonium Grice, J.D., Groat, L.A. and Roberts, A.C. (1996) divanadium(IV,V) tellurium(IV) heptaoxide. Acta Jensenite, a cupric tellurate framework structure with Crystallographica, E70,27–30. two coordinations of copper. The Canadian Hawthorne, F.C. (1984) The crystal structure of mandar- 3+ Mineralogist, 34,55–59. inoite, Fe2 Se3O9 ·6H2O. The Canadian Grigor’ev, M.S., Struchkov, Yu.T., Fedoseev, A.M., Mineralogist, 22, 475–480. Yusov, A.B. and Yanovskii, A.I. (1992) Synthesis, Hawthorne, F.C. (2014) The structure hierarchy hypoth- X-ray and luminescence study of some rare earths with esis. Mineralogical Magazine, 78, 957–1027. iodo- and telluromolybdate-ions complexes. Zhurnal Hawthorne, F.C. and Ferguson, R.B. (1975) Refinement Neorganicheskoi Khimii, 37, 2507–2514. of the crystal structure of cryolite. The Canadian Grundler, P.V., Brugger, J., Meisser, N., Ansermet, S., Mineralogist, 13, 377–382. Borg, S., Etschmann, B., Testemale, D. and Bolin, T. Hawthorne, F.C., Ercit, T.S. and Groat, L.A. (1986) 4+ (2008) Xocolatlite, Ca2Mn2 Te 2O12 ·H2O, a new Structures of zinc selenite and copper selenite. Acta tellurate related to kuranakhite: description and Crystallographica, C42, 1285–1287. measurement of Te by XANES Hawthorne, F.C., Burns, P.C. and Grice, J.D. (1996) The spectroscopy. American Mineralogist, 93, 1911–1920. crystal chemistry of . Pp. 41–115 in: Boron: Grzechnik, A., Halasyamani, P.S.,Chang, H.Y.and Friese, Mineralogy, Petrology, and Geochemistry (L.M. K. (2009) Twinned crystal structure and compressibil- Anovitz and E.S. Grew, editors) Reviews in ity of TlTeVO4. Journal of Solid State Chemistry, 182, Mineralogy & Geochemistry, 33. Mineralogical 1570–1574. Society of America, Washington, DC. Grzechnik, A., Halasyamani, P.S., Kim, J.-H. and Friese, Hawthorne, F.C., Krivovichev, S.V. and Burns, P.C. K. (2010) (NH4)2WTe2O8 at 5.09 GPa: A single- (2000) The crystal chemistry of sulfate minerals. Pp. crystal study using synchrotron radiation. Acta 1–112 in: Sulfate Minerals: Crystallography, Crystallographica, C66, i79–i81. Geochemistry, and Environmental Significance (C.N. Gu, Q.H., Hu, C.L., Zhang, J.H. and Mao, J.G. (2011) A Alpers, J.L. Jambor and D.K. Nordstrom, editors) series of new phases in the alkali metal-Nb(V)/Ta(V)- Reviews in Mineralogy & Geochemistry, 40. Se(IV)/Te(IV)-O systems. Dalton Transactions, 40, Mineralogical Society of America and the 2562–2569. Geochemical Society, Chantilly, Virginia, USA. Guesdon, A. and Raveau, B. (2000) A series of Mo (VI) Hazen, R.M., Finger, L.W. and Mariathasen, J.W.E. monophosphates involving the lone pair cation Te(IV): (1985) High-pressure crystal chemistry of

529 A. G. CHRISTY ET AL.

scheelite-type tungstates and molybdates. Journal of Hottentot, D. and Loopstra, B.O. (1983) The structure of Physics and Chemistry of Solids, 46, 253–263. tribarium undecaoxotetratellurate (IV), Ba3Te 4O11. He, X.H., Huang, C.C., Sheng, L.D. and Qian, L.Z. Acta Crystallographica, C39, 320–322. (2010) Synthesis and characterization of new open- Hou, J.-Y.,Huang, C.-C., Zhang, H.-H., Yang, Q.-Y., Chen, framework vanadium tellurite featuring an unprece- Y.-P. and Xu, J.-F. (2005) Barium divanadium(V) V dented (3,7)-connected network: K3((V O4) tellurite(IV). Acta Crystallographica, C61,i59–i60. IV (V O)4(TeO3)4)·(H2O)4. Crystal Growth and Hou, J., Huang, C.C., Zhang, H., Tu, C., Sun, R. and Design, 10, 2021–2024. Yang, Q. (2006) A new noncentrosymmetric tellurite: n Hector, A.L., Hill, N.J., Levason, W. and Webster, M. BaMo2Te 2O11(H2O) with (Mo(1)Mo(2)O10) spiral (2002) X-Ray crystal structures of hexa-oxotellurate chains. Journal of Molecular Structure, 785,37–42. complexes of (VI) and silver(III): Housley, R.M., Kampf, A.R., Mills, S.J., Marty, J. and Na6[RuO2{TeO4(OH)2}2] · 16H2O and Na5[Ag Thorne, B. (2011) The remarkable occurrence of rare {TeO4(OH)2}2] · 16H2O. Zeitschrift für anorganische secondary minerals at Otto Mountain near Baker, und allgemeine Chemie, 628, 815–818. California – including seven new species. Rocks & Helmholtz, L. (1936) The crystal structure of the low Minerals, 86, 132–142. temperature modification of thallous iodide. Howard, C.J. and Carpenter, M.A. (2010) Octahedral Zeitschrift für Kristallographie, 95, 129–137. tilting in cation-ordered Jahn-Teller distorted Hepworth, M.A., Jack, K.H., Peacock, R.D. and perovskites – a group-theoretical analysis. Acta Westland, G.J. (1957) The crystal structures of the Crystallographica, B66,40–50. trifluorides of iron, cobalt, ruthenium, , Howard, C.J., Sabine, T.M. and Dickson, F. (1991) and . Acta Crystallographica, 10, Structural and thermal parameters for rutile and 63–69. anatase. Acta Crystallographica, B47, 462–468. Hesse, K.-F. and Liebau, F. (1980) Crystal chemistry of Howard, C.J., Kennedy, B.J. and Woodward, P.M. (2003) silica-rich barium silicates. III. Refinement of the Ordered double perovskites – a group-theoretical crystal structures of the layer silicates Ba2[Si4O10](l) analysis. Acta Crystallographica, B59, 463–471. (sanbornite) and Ba2[Si4O10] (h). Zeitshcrift für Huminicki, D.M.C. and Hawthorne, F.C. (2001) Kristallografie, 153,33–41. Refinement of the crystal structure of swedenborgite. Hill, R.J. (1985) Refinement of the structure of ortho- The Canadian Mineralogist, 39, 153–158. rhombic PbO (massicot) by Rietveld analysis of Hyde, B.G. and Andersson, S. (1989) Inorganic Crystal neutron powder diffraction data. Acta Structures. Wiley-Interscience. 430 pp. Crystallographica, C41, 1281–1284. Isasi, J. (2001) New MM′O4 oxides derived from the rutile Hoekstra, H.R. and Marshall, R.H. (1967) Some uranium- type: synthesis, structure and study of magnetic and double oxides. Advances in electronic properties. Journal of Alloys and Chemistry, 71,211–227. Compounds, 322,89–96. Hofmann, W. and Jäniche, W. (1935) Der Strukturtyp von IUPAC (1997) Compendium of Chemical Terminology, Aluminiumborid, AlB2. Naturwissenschaften, 23,851. 2nd edition. [the “Gold Book”]. Compiled by Höss, P. and Schleid, T. (2007a)Y2TeO 6 with the A.D. McNaught and A. Wilkinson. Blackwell La2TeO 6-type structure. Acta Crystallographica, Scientific Publications, Oxford, UK. XML on-line E63, i133–i135. corrected version: http://goldbook.iupac.org (2006–) Höss, P. and Schleid, T. (2007b)Sc2Te 5O13 und Sc2TeO 6: created by M. Nic, J. Jirat, B. Kosata; updates die ersten Oxotellurate des Scandiums. Zeitschrift für compiled by A. Jenkins. ISBN 0-9678550-9-8. anorganische und allgemeine Chemie, 633, doi:10.1351/goldbook. 1391–1396. Ivanov, S.A., Nordblad, P., Mathieu, R., Tellgren, R. and Höss, P., Starkulla, G. and Schleid, T.(2005) (III) Ritter, C. (2010a) Neutron diffraction studies and the oxotellurate(IV), Lu2Te 4O11. Acta Crystallographica, magnetism of an ordered perovskite: Ba2CoTeO6. E61,i113–i115. Dalton Transactions, 39, 5490–5499. Höss, P., Osvet, A., Meister, E., Batentschuk, M., Ivanov, S.A., Nordblad, P., Mathieu, R., Tellgren, R. and Winnacker, A. and Schleid, T. (2008) Synthesis, Ritter, C. (2010b) Structural and magnetic properties crystal structures and luminescence properties of the of the ordered perovskite Pb2CoTeO6. Dalton 3+ 39 – Eu -doped yttrium oxotellurates(IV) Y2Te 4O11 and Transactions, , 11136 11148. Y2Te 5O13. Journal of Solid State Chemistry, 181, Ivanov, S.A., Mathieu, R., Nordblad, P., Politova, E., 2783–2788. Tellgren, R., Ritter, C. and Proidakova, V. (2012a) Hottentot, D. and Loopstra, B.O. (1979) Structures of Structural and magnetic properties of Mn3–xCdxTeO 6 calcium tellurate, CaTeO4, and tellurate, (x = 0, 1, 1.5 and 2). Journal of Magnetism and SrTeO4. Acta Crystallographica, B35, 728–729. Magnetic Materials, 324, 1637–1644.

530 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

Ivanov, S.A., Tellgren, R., Ritter, C., Nordblad, P., tellurite-containing Mo4 clusters. Inorganic Mathieu, R., Andre, G., Golubko, N.V., Politova, E. Chemistry, 46, 6495–6501. D. and Weil, M. (2012b) Temperature-dependent Jiang, H., Kong, F. and Mao, J.-G. (2007c) Synthesis, multi-k magnetic structure in multiferroic Co3TeO 6. crystal and band structures, and optical properties of a Materials Research Bulletin, 47,63–72. new lanthanide-alkaline earth tellurium(IV) oxide: Iwanaga, D., Inaguma, Y. and Itoh, M. (1999) Crystal La2Ba(Te3O8)(TeO3)2. Journal of Solid State structure and magnetic properties of B-site ordered Chemistry, 180, 1764–1769. perovskite-type oxides A2CuB’O6 (A = Ba, Sr; B′ =W, Jiang, H., Huang, S.P., Fan, Y., Mao, J.-G. and Cheng, W. Te). Journal of Solid State Chemistry, 147, 291–295. D. (2008) Explorations of new types of second order Iwanaga, D., Inaguma, Y. and Itoh, M. (2000) Structure nonlinear optical materials in Cd(Zn)-VV-TeIV-O – 14 and magnetic properties of Sr2NiAO6 (A = W, Te). systems. Chemistry A European Journal, , Materials Research Bulletin, 35, 449–457. 1972–1981. Jacoboni, C., Leble, A. and Rousseau, J.J. (1981) Johansson, G.B. (1978) Diammonium ditellurium (IV) Détermination précise de la structure de la chiolite pentaoxide dihydrate. Acta Crystallographica, B34, 3+ – Na5Al3F14 et étude par R.P.E. de Na5Al3F14:Cr . 2830 2832. Journal of Solid State Chemistry, 36, 297–304. Johansson, G.B. and Lindqvist, O. (1976) The crystal Jacobson, A.J., Scanlon, J.C., Poeppelmeier, K.R., Longo, structure of Al2(OH)2TeO 3SO4. Acta J.M. and Cox, D.E. (1981) The preparation and Crystallographica, B32, 407–411. characterization of Ba3Te 2O9: a new oxide structure. Johansson, G.B. and Lindqvist, O. (1977) The crystal Materials Research Bulletin, 16, 359–367. structure of ammine copper (II) tellurate (IV) mono- Jeansannetas, B., Thomas, P., Champarnaud-Mesjard, J. hydrate Cu(NH3)TeO3 ·H2O. Acta Crystallographica, B33 – C. and Frit, B. (1997) Crystal structure of Tl2Te 3O7. , 2418 2421. Materials Research Bulletin, 32,51–58. Johansson, G.B. and Lindqvist, O. (1978) The crystal Jeansannetas, B., Thomas, P., Champarnaud-Mesjard, J. structure of dipotassium tellurate (IV) trihydrate, B34 C. and Frit, B. (1998) Crystal structure of α-Tl2Te 2O5. K2TeO 3 ·3H2O. Acta Crystallographica, , Materials Research Bulletin, 33, 1709–1716. 2959–2962. Jensen, E.P. and Barton, M.D. (2000) Gold deposits Johansson, G.B., Lindqvist, O. and Moret, J. (1979) related to alkaline magmatism. Reviews in Economic Diammonium tellurium (VI) dioxide tetrahydroxide. Geology, 13, 279–314. Acta Crystallographica, B35, 1684–1686. Jiang, H.-L. and Mao, J.-G. (2006a) [Cd2(Te6O13)] Johnston, M.G. and Harrison, W.T. (2002) Manganese β E58 [Cd2Cl6] and Cd7Cl8(Te7O17): Novel tellurium(IV) tellurite, -MnTe2O5. Acta Crystallographica, , oxide slabs and unusual cadmium chloride architec- i59–i61. tures. Inorganic Chemistry, 45, 717–721. Johnston, M.G. and Harrison, W.T.A. (2007) Li Jiang, H.-L. and Mao, J.-G. (2006b) New members in the (VO2)3(TeO3)2. Acta Crystallographica, C63, i57–i59. Ni(n+1)(QO3)nX2 family: unusual 3D network based on Johnsson, M. and Törnroos, K.W. (2003a) A synthetic Ni4ClO3 cubane-like clusters in Ni7(TeO3)6Cl. zinc tellurium oxochloride, Zn2(TeO3)Cl2. Acta Inorganic Chemistry, 45, 7593–7599. Crystallographica, C59, i53–i54. Jiang, H. and Mao, J.-G. (2006c) Synthesis, crystal Johnsson, M. and Törnroos, K.W. (2003b) Synthesis and structure and characterization of the barium zinc crystal structure of the layered compound CuZn(TeO3) tellurate disilicate: Ba3Zn6[TeO6][Si2O7]2. Cl2. Solid State Sciences, 5, 263–266. Zeitschrift für anorganische und allgemeine Johnsson, M., Törnroos, K.W., Mila, F. and Millet, P. Chemie, 632, 2053–2057. (2000) Tetrahedral clusters of copper(II): Jiang, H. and Mao, J.-G. (2008) Syntheses, crystal crystal structures and magnetic properties of structures and optical properties of the first strontium Cu2Te 2O5X2 (X = Cl, Br). Chemistry of Materials, (IV) and tellurium(IV) oxychlorides: 12, 2853–2857. Sr3(Se3O3)(Se2O5)Cl2 and Sr4(Te3O8)Cl4. Journal of Johnsson, M., Törnroos, K.W., Lemmens, P.and Millet, P. Solid State Chemistry, 181, 345–354. (2003) Crystal structure and magnetic properties of a Jiang, H., Feng, M.L. and Mao, J.-G. (2006) Synthesis, new two-dimensional S = 1 quantum system crystal structures and characterizations of BaZn Ni5(TeO3)3X2 (X = Cl, Br). Chemistry of Materials, (SeO3)2 and BaZn(TeO3)Cl2. Journal of Solid State 15,68–73. Chemistry, 179, 1911–1917. Johnsson, M., Lidin, S., Törnroos, K.W., Bürgi, H.B. and Jiang, H.-L., Ma, E. and Mao, J.-G. (2007a)New Millet, P. (2004) Host-guest compounds in the family luminescent solids in the Ln-W-(Mo)-Te-O (Cl) of tellurium-nickel oxohalogenides. Angewandte systems. Inorganic Chemistry, 46, 7012–7023. Chemie International Edition, 43, 4292–4295. Jiang, H.-L., Xie, Z. and Mao, J.-G. (2007b)Ni3(Mo2O8) Kalinina, I.V., Izarova, N.V. and Kortz, U. (2012) Bis (XO3)(X = Se, Te): The first nickel selenite- and [tetraruthenium(IV)]-containing polyoxometalates:

531 A. G. CHRISTY ET AL.

IV 4– [{Ru4 O6(H2O)9}2Sb2W20O68(OH)2] and polyhedral sheets. American Mineralogist, 98, IV – [{Ru4 O6(H2O)9}2{Fe(H2O)2}2{β-TeW9O33}2H] . 512–517. Inorganic Chemistry, 51, 7442–7444. Kampf, A.R., Mills, S.J., Housley, R.M., Rossman, G.R., Kampf, A.R. and Mills, S.J. (2011) The role of hydrogen Marty, J. and Thorne, B. (2013c) Lead-tellurium in tellurites: crystal structure refinements of juabite, oxysalts from Otto Mountain near Baker, California: 2+ 6+ poughite and rodalquilarite. Journal of Geosciences, X. Bairdite, Pb2Cu4 Te 2 O10(OH)2(SO4)(H2O), a new 56, 235–247. mineral with thick HCP layers. American Kampf, A.R., Housley, R.M., Mills, S.J., Marty, J. and Mineralogist, 98, 1315–1321. Thorne, B. (2010a) Lead-tellurium oxysalts from Otto Kampf, A.R., Mills, S.J., Housley, R.M., Rossman, G.R., Mountain near Baker, California: I. Ottoite, Pb2TeO 5, Marty, J. and Thorne, B. (2013d) Lead-tellurium a new mineral with chains of tellurate octahedra. oxysalts from Otto Mountain near Baker, California: 95 – 2+ 6+ American Mineralogist, , 1329 1336. XI. Eckhardite, (Ca,Pb)Cu Te O5(H2O), a new Kampf, A.R., Marty, J. and Thorne, B. (2010b) Lead- mineral with HCP stair-step layers. American tellurium oxysalts from Otto Mountain near Baker, Mineralogist, 98, 1617–1623. California: II. Housleyite, Pb6CuTe4O18(OH)2, a new Kampf, A.R., Cooper, M.A., Mills, S.J., Housley, R.M. mineral with Cu-Te octahedral sheets. American and Rossman, G.R. (2016) Lead–tellurium oxysalts Mineralogist, 95, 1337–1342. from Otto Mountain near Baker, California: XII. 2+ 6+ Kampf, A.R., Housley, R.M. and Marty, J. (2010c) Lead- Andychristyite, PbCu Te O5(H2O), a new mineral tellurium oxysalts from Otto Mountain near Baker, with HCP stair-step layers. Mineralogical Magazine, 6+ California: III. Thorneite, Pb6(Te2 O10)(CO3) DOI: 10.1180/minmag.2016.080.042. Cl2(H2O), the first mineral with edge-sharing octahe- Kashi, T., Yasiu, Y., Moyoshi, T., Sato, M., Kakurai, K., dral tellurate dimers. American Mineralogist, 95, Iikubo, S. and Igawa, N. (2008) Crystal structure and 1548–1553. magnetic properties of CoZn(TeO3)Br2. Journal of the Kampf, A.R., Mills, S.J., Housley, R.M., Marty, J. and Physical Society of , 77, 084707-1–084707-5. Thorne, B. (2010d) Lead-tellurium oxysalts from Otto Kasper, H.M. (1969) LnCrTeO6 – a new series of Mountain near Baker, California: IV. Markcooperite, compounds based on the PbSb2O6 structure. 6+ 4 – Pb(UO2)Te O6, the first natural uranyl tellurate. Materials Research Bulletin, ,33 37. American Mineralogist, 95, 1554–1559. Kear, B.H. and Wilsdorf, H.G.F. (1962) Dislocation Kampf, A.R., Mills, S.J., Housley, R.M., Marty, J. and configurations in plastically deformed polycrystalline Thorne, B. (2010e) Lead-tellurium oxysalts from Otto Cu3Au alloys. Transactions of the AIME, 224, Mountain near Baker, California: V. Timroseite, 382–386. 2+ 6+ 2+ Pb2Cu5 (Te O6)2(OH)2, and paratimroseite, Pb2Cu4 Keggin, J.F. (1934) The structure and formula of 12- 6+ (Te O6)2(H2O)2, two new tellurates with Te-Cu phosphotungstic acid. Proceedings of the Royal polyhedral sheets. American Mineralogist, 95, Society of London, Series A, 144,75–100. 1560–1568. Kholodkovskaya, L.N., Dolgikh, V.A. and Popovkin, B. Kampf, A.R., Mills, S.J., Housley, R.M., Marty, J. and A. (1991) Crystal structure of bismuth-tellurium Thorne, B. (2010f ) Lead-tellurium oxysalts from Otto oxobromide Bi0.97TeO 3Br0.90. Zhurnal Mountain near Baker, California: VI. Telluroperite, Neorganicheskoi Khimii, 36, 2205–2209. 4+ Pb3Te O4Cl2, the Te analog of perite and nadorite. Kholodkovskaya, L.N., Dolgikh, V.A. and Popovkin, B. American Mineralogist, 95, 1569–1573. A. (1996) The crystal structure of the new pyroelectric Kampf, A.R., Mills, S.J., Housley, R.M., Rumsey, phase Bi4Te 2O9Br2. Journal of Solid State Chemistry, M.S. and Spratt, J. (2012) Lead-tellurium oxysalts 116, 406–408. from Otto Mountain near Baker, California: VII. Kikuta, T., Hamatake, D., Yamazaki, T. and Nakatani, N. Chromschieffelinite, Pb10Te 6O20(OH)14(CrO4)(H2O)5, (2005) Crystal structure of telluric acid ammonium the chromate analog of schieffelinite. American phosphate (TAAP) in the paraelectric phase. Journal Mineralogist, 97,212–219. of the Korean Physical Society, 46,211–216. Kampf, A.R., Mills, S.J., Housley, R.M. and Marty, J. Kim, A.A., Zayakina, N.V. and Makhotko, V.F. (1990) (2013a) Lead-tellurium oxysalts from Otto Mountain Kuksite, Pb3Zn3TeO 6(PO4)2, and cheremnykhite, 2+ 6+ near Baker, California: VIII. Fuettererite, Pb3Cu6 Te Pb3Zn3TeO 6(VO4)2, – new tellurates from the O6(OH)7Cl5, a new mineral with double spangolite- Kuranakh gold deposit (central Aldan, southern type sheets. American Mineralogist, 98, 506–511. Yakutia [Sakha]). Zapiski Rossiyskogo Kampf, A.R., Mills, S.J., Housley, R.M. and Marty, J. Mineralogicheskogo Obshchestva, 119,50–57. (2013b) Lead-tellurium oxysalts from Otto Mountain Kim, J.H. and Halasyamani, P.S. (2008) A rare multi- 2+ 6+ near Baker, California: IX. Agaite, Pb3Cu Te coordinate tellurite, NH4ATe 4O9 ·2H2O(A =Rb or O5(OH)2(CO3), a new mineral with CuO5-TeO6 Cs): The occurence of TeO3,TeO4, and TeO5

532 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

polyhedra in the same material. Journal of Solid State Kocak, M., Platte, C. and Trömel, M. (1979b) Chemistry, 181, 2108–2112. Bariumhexaoxoditellurat (IV, VI): Kim, J.H., Baek, J. and Halasyamani, P.S. (2007a) Sauerstoffkoordinationszahl fünf am vierwertigen B35 – (NH4)2Te 2WO8: a new polar oxide with second- Tellur. Acta Crystallographica, , 1439 1441. harmonic generating, ferroelectric, and pyroelectric Köhl, P. (1973) Die Kristallstruktur von Perowskiten II II VI properties. Chemistry of Materials, 19, 5637–5641. A2 Ni M O6. II. Das Sr2NiWO6. Zeitschrift für Kim, H., Cho, Y., Yun, H. and Do, J. (2007b) anorganische und allgemeine Chemie, 401, 121–131. Hydrothermal synthesis of a new vanadium tellurate Köhl, P. and Reinen, D. (1974) Strukturelle und (VI) with a novel chain structure: spektroskopische Untersuchungen am Ba2CuTeO6. (NH4)4{(VO2)2[Te2O8(OH)2]} · 2(H2O). Zeitschrift Zeitschrift für anorganische und allgemeine Chemie, für anorganische und allgemeine Chemie, 633, 409, 257–272. 473–477. Kohn, K., Inoue, K., Horie, O. and Akimoto, S.I. (1976) Kim, M.K., Kim, S.-H., Chang, H.-Y., Halasyamani, P.S. Crystal chemistry of MSeO3 and MTeO3 (M = Mg, and Ok, K.M. (2010) New noncentrosymmetric Mn, Co, Ni, Cu and Zn). Journal of Solid State tellurite phosphate material: synthesis, characteriza- Chemistry, 18,27–37. tion, and calculations of Te2O(PO4)2. Inorganic Kondratyuk, I.P., Muradyan, L.A., Pisarevskii, Y.V. and Chemistry, 49, 7028–7034. Simonov, V.I. (1987) Precision X-ray structure inves- Kim, Y.H., Lee, D.W. and Ok, K.M. (2014a) tigation of acoustooptical single of α-TeO2. Noncentrosymmetric YVSe2O8 and centrosymmetric Kristallografiya, 32, 354. YVTe2O8: macroscopic centricities influenced by the Kong, F., Jiang, H. and Mao, J.G. (2008) size of lone pair cation linkers. Inorganic Chemistry, La4(Si5.2Ge2.8O18)(TeO3)4 and La2(Si6O13)(TeO3)2: 53, 1250–1256. Intergrowth of the (III) tellurite layer with Kim, Y.H., Lee, D.W. and Ok, K.M. (2014b) Strong the XO4 (X = Si/Ge) tetrahedral layer. Journal of Solid second harmonic generation (SHG) originating from State Chemistry, 181, 263–268. combined second-order Jahn-Teller (SOJT) distortive Kong, F., Hu, C., Hu, T., Zhou, Y. and Mao, J.G. (2009) cations in a new noncentrosymmetric tellurite, InNb Explorations of new phases in the Ga(III)/In(III)-Mo 53 – (TeO4)2. Inorganic Chemistry, , 5240 5245. (VI)-Se(IV)/Te(IV)-O systems. Dalton Transactions, Klein, W., Curda, J., Peters, E.M. and Jansen, M. (2005a) 2009, 4962–4970. Disilberoxotellurat(VI), Ag2TeO 4. Zeitschrift für Kong, F., Xu, X. and Mao, J.-G. (2010) A series of new anorganische und allgemeine Chemie, 631, 723–727. ternary and quaternary compounds in the Li(I)-Ga Klein, W., Curda, J., Peters, E.M. and Jansen, M. (2005b) (III)-Te(IV)-O System. Inorganic Chemistry, 49, Neue Silber(I)-oxotellurate(IV/VI). Zeitschrift für 11573–11580. anorganische und allgemeine Chemie, 631, Kortz, U., Al-Kassem, N.K., Savelieff, M.G., Al Kadi, N. 2893–2899. A. and Sadakane, M. (2001) Synthesis and Klein, W., Curda, J., Peters, E.M. and Jansen, M. (2006) characterization of copper, zinc, manganese and Ag2Te 2O7, ein neues Silbertellurat mit Weberit- cobalt-substituted, dimeric heteropolyanions, ((α- n– III III Struktur. Zeitschrift für anorganische und allgemeine XW9O33)2M3(H2O)3) )(n = 12, X =As ,Sb , M = Chemie, 632, 1508–1513. Cu2+,Zn2+; n = 10, X =SeIV,TeIV, M =Cu2+). Klein, W., Curda, J. and Jansen, M. (2007) Crystal Inorganic Chemistry, 40, 4742–4749. structure and properties of Ag4CuTeO6. Zeitschrift für Kramer, V. and Brandt, G. (1985) Structure of cadmium anorganische und allgemeine Chemie, 633, 231–234. tellurate (IV), CdTeO3. Acta Crystallographica, C41, Kleppe, A.K., Welch, M.D., Crichton, W.A. and Jephcoat, 1152–1154. A.P.(2012) Phase transitions in hydroxide perovskites: Kramer, V. and Brandt, G. (1986) Structure of a Raman spectroscopic study of stottite, FeGe(OH)6, mercury tellurate (IV). Acta Crystallographica, C42, to 21 GPa. Mineralogical Magazine, 76, 949–962. 917–918. Knapp, M.C. (2006) Investigations into structure and Kratochvil, B. (1986) The achieved results in the properties of ordered perovskites, layered perovskites, determination of the crystal structure of NaH5TeO 6. and defect pyrochlores. Unpublished PhD Thesis, Sbornik Vysoke Skoly Chemicko – Technologicke v Ohio State University, USA, 161 pp. Praze, G: Mineralogie, 22,53–69. Knop, O., Cameron, T.S. and Jochem, K. (1982) What is Kratochvil, B. and Jensovsky, L. (1977) The crystal the true space group of weberite? Journal of Solid structure of sodium metatellurate. Acta State Chemistry, 43, 213–221. Crystallographica, B33, 2596–2598. Kocak, M., Platte, C. and Trömel, M. (1979a) Ueber Kratochvil, B., Podlahova, J. and Jensovsky, L. (1978) verschiedene Formen von BaTeO3. Zeitschrift für Sodium potassium ditellurate(VI) hexahydrate. Acta anorganische und allgemeine Chemie, 453,93–97. Crystallographica, B34, 256–258.

533 A. G. CHRISTY ET AL.

Krishnan, K., Mudher, K.S. and Venugopal, V. (2000) Larson, A.C. and Cromer, D.T. (1961) The crystal Structural and thermal studies on PuTe2O6. Journal of structure of CeCu2. Acta Crystallographica, 14, Alloys and Compounds, 307,114–118. 73–74. Krivovichev, S.V. (2008) Minerals with antiperovskite Laval, J.P. and Boukharrata, N.J. (2009) New vanadium structure: a review. Zeitschrift für Kristallographie, (IV) and (IV) oxyfluorotellurates(IV): 223, 109–113. V2Te 2O7F2 and TiTeO3F2. Acta Crystallographica, Krivovichev, S.V. and Brown, I.D. (2001) Are the C65,i1–i6. compressive effects of encapsulation an artifact of Laval, J.P., Jennene Boukharrata, N. and Thomas, P. the bond valence parameters? Zeitschrift für (2008) New oxyfluorotellurates(IV): MTeO 3F(M =Fe Kristallographie, 216, 245–247. (III), Ga(III) and Cr(III)). Acta Crystallographica, Krivovichev, S.V., Mentré, O., Siidra, O.I., Colmont, M. C64, i12–i14. and Filatov, S.K. (2013) Anion-centred tetrahedra in Lee, D.S. and Edmond, J.M. (1985) Tellurium species in inorganic compounds. Chemical Reviews, 113, seawater. Nature, 313, 782–785. 6459–6535. Lee, D.W., Oh, S.-J., Halasyamani, P.S. and Ok, K.M. Ktari, L., Dammak, M., Mhiri, T. and Kolsi, A.W. (2002) (2011) New quaternary tellurite and selenite: synthe- Characterization and structure determination of dis- sis, structure, and characterization of centrosymmetric ordered rubidium ammonium sulfate tellurate InVTe2O8 and noncentrosymmetric InVSe2O8. Rb1.12(NH4)0.88SO4·(Te(OH)6). Physical Chemistry Inorganic Chemistry, 50, 4473–4480. News, 8,1–8. Lee, D.W., Bak, D.-B., Kim, S.B., Kim, J. and Ok, K.M. Ktari, L., Dammak, M., Hadrich, A., Cousson, A., (2012) Effect of the framework flexibility on the Nierlich, M., Romain, F. and Mhiri, T. (2004) centricities in centrosymmetric In2Zn(SeO3)4 and Structural, vibrational and dielectric properties of the noncentrosymmetric Ga2Zn(TeO3)4. Inorganic new mixed solution K0.84(NH4)1.16SO4·(Te(OH)6). Chemistry, 51, 7844–7850. Solid State Sciences, 6, 1393–1401. Léger, J.M., Haines, J. and Atouf, A. (1996) The high Ktari, L., Abdelhedi, M., Bouhlel, N., Dammak, M. and pressure behaviour of the cotunnite and post-cotunnite Cousson, A. (2009) Synthesis, calorimetric, structural phases of PbCl2 and SnCl2. Journal of Physics and and conductivity studies in a new thallium selenate Chemistry of Solids, 57,7–16. tellurate adduct compound. Materials Research Levason, W. and Webster, M. (1998) Pentasodium Bulletin, 44, 1792–1796. bis [dihydroxytetraoxotellurium (VI)] gold (III) hex- Kunnmann, W., La Placa, S.J., Corliss, L.M., Hastings, J. adecahydrate. Acta Crystallographica, C54, M. and Banks, E. (1968) Magnetic structures of the 1729–1731. ordered trirutiles Cr2WO6,Cr2TeO 6 and Fe2TeO 6. Levason, W., Spicer, M.D. and Webster, M. (1988) Co- Journal of Physics and Chemistry of Solids, 29, ordination chemistry of higher oxidation states. Part 1356–1364. 26. Spectroscopic studies of tellurate complexes of the Kyung, K.M., Vinna, J., Woo, L.D. and Min, O.K. (2010) trivalent group 1b metals. X-ray structure of Na5(Cu Anionic templating in a new layered bismuth tellurium (TeO4(OH)2)2).16(H2O). Dalton Transactions, 5, oxychloride, Bi3Te 4O10Cl5. Dalton Transactions, 39, 1377–1381. 6037–6042. Levason, W., Spicer, M.D. and Webster, M. (1991) Lafuente, B., Yang, H. and Downs, R.T. (2015) Crystal Coordination chemistry of higher oxidation states. 2+ 4+ structure of tetrawickmanite, Mn Sn (OH)6. Acta Part 37. Tellurato complexes of palladium(IV) and Crystallographica, E71, 234–237. platinum(IV). Crystal structures of Laligant, Y.(2001) X-ray and TEM studies of CdTeMoO6 Na8K2H4(Pd2Te 4O24H2)·20H2O and K6Na2(Pt and CoTeMoO6: a new superstructure of fluorite type (OH)2(HTeO6)2)·12H2O. Inorganic Chemistry, 30, with cation and anion deficiencies (CoTeMo)(2O6). 967–971. Journal of Solid State Chemistry, 160, 401–408. Levason, W., Oldroyd, R.D. and Webster, M. (1994) Lam, A.E., Groat, L.A. and Ercit, T.S. (1998) The crystal Extended x-ray absorption fine structure studies of 6+ structure of dugganite, Pb3Zn3Te As2O14. The transition-metal periodate and tellurate complexes. Canadian Mineralogist, 36, 823–830. Crystal structure of Rb2Na4(OsO2(H2TeO 6)2).16 Lam, A.E., Groat, L.A., Grice, J.D. and Ercit, T.S. (1999) (H2O). Dalton Transactions, 20, 2983–2988. The crystal structure of choloalite. The Canadian Levinson, A.A. (1974) Introduction to Exploration Mineralogist, 37, 721–729. Geochemistry. Applied Publishing, Calgary, Canada, Lammers, P.and Zemann, J. (1965) Beiträge zur Kenntnis 611 pp. der Alkalitellurate. I. Über ein neues Alkalitellurat und Li, G., Xue, Y. and Xiong, M. (2014) Tewite, IMA 2014- seinen Strukturtyp. Zeitschrift für anorganische und 053. CNMNC Newsletter No. 22, Mineralogical allgemeine Chemie, 334, 225–234. Magazine, 78, 1241–1248.

534 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

Liebau, F. (1985) Structural Chemistry of Silicates. dichromate and thallous uranyl phosphate hydrate. Structure, Bonding and Classification. Springer- Zeitschrift für Kristallographie, 219, 259–266. Verlag, Berlin – Heidelberg, 347 pp. Loeksmanto, W., Moret, J., Maurin, M. and Philippot, E. Limanski, E.M., Drewes, D., Droste, E., Bohner, R. and (1980) Etude cristallochimique comparée et Krebs, B. (2003) Syntheses and X-ray characteriza- conductivité électrique de deux tellurates mixtes: IV VI IV VI tion of novel tellurium-substituted lacunary poly- AgxNa2−xTe 2 Te 3 O14 (X = 0, 4) et K2Te Te 3 O12. oxotungstates containing VIV,CoII,NiII and ZnII as Journal of Solid State Chemistry, 33, 209–217. heteroatoms. Journal of Molecular Structure, 656, Loopstra, B.O. and Goubitz, K. (1986) The structures of 17–25. four caesium tellurates. Acta Crystallographica, C42, Lin, W.-F., Xing, Q.-J., Ma, J., Zou, J.-P., Lei, S.-L., Luo, 520–523. X.-B. and Guo, G.-C. (2013) Synthesis, band and Lopez, M.L., Veiga, M.L., Jerez, A. and Pico, C. (1991) crystal structures, and optical properties of the ternary Synthesis and crystal structure of MTe 2O6 (M =Ce, compound Mg2Te 3O8. Zeitschrift für anorganische Th). Journal of the Less-Common Metals, 175, und allgemeine Chemie, 639,31–34. 235–241. Linda, D., Dutreilh-Colas, M., Loukil, M., Mirgorodsky, Lopez, M.L., Jerez, A., Pico, C., Saez-Puche, R. and A., Masson, O., Duclere, J.R., Thomas, P. and Veiga, M.L. (1993a) Synthesis, Crystal structure, and Kabadou, A. (2010) Crystal structure and dynamical magnetic susceptibility of MLnLiTeO6, M = Ca, Sr, properties of a new tellurite: AgTlTeO3. Materials Ba. Journal of Solid State Chemistry, 105,19–26. Research Bulletin, 45, 1883–1888. Lopez, M.L., Alvarez, I., Gaitan, M., Jerez, A., Pico, C. Lindqvist, O. (1969) The crystal structure of the tellurate and Veiga, M.L. (1993b) Structural study and Na2K4[Te2O8(OH)2](H2O)14. Acta Chemica magnetic measurements of some perovskites 23 – 63 – Scandinavica, , 3062 3070. MLnLiTeO6. Solid State Ionics, , 599 602. Lindqvist, O. (1970) The crystal structure of telluric acid, Lorenzo-Luis, P.A.,Martin-Zarza, P., Gili, P., Saez-Puche, Te(OH)6 (mon). Acta Chemica Scandinavica, 24, R., Jimenez-Jimenez, J., Rodriguez-Castellon, E., 3178–3188. Ruiz Perez, C., Gonzalez-Platas, J. and Solans, X. Lindqvist, O. (1972a) The crystal structure of CuTeO3. (1997) Synthesis and characterisation of the molyb- 26 – II Acta Chemica Scandinavica, , 1423 1430. dotellurates: (M(H2O)6)3 · (TeMo6O24): M =Ni and Lindqvist, O. (1972b) A redetermination of the crystal CoII. European Journal of Solid State Inorganic structure of KTeO3(OH). Acta Chemica Scandinavica, Chemistry, 34, 1259–1271. 26, 4109–4120. Ma, C., Tschauner, O., Beckett, J.R., Rossmann, G.R. and Lindqvist, O. and Moret, J. (1973) The crystal structure of Liu, W.J. (2013) Kangite, (Sc,Ti,Al,Zr,Mg,Ca,)2O3, a tellurium (IV, VI) oxyhydroxide, H2Te 2O6. Acta a new ultra-refractory scandia mineral from the Crystallographica, B29, 956–963. : synchrotron micro-Laue diffraction Lindqvist, O., Mark, W. and Moret, J. (1975) The crystal and electron backscatter diffraction. American 98 – structure of Te4O9. Acta Crystallographica, B31, Mineralogist, , 870 878. 1255–1259. Ma, C., Beckett, J.R. and Rossman, G.R. (2014) Ling, J., Ward, M. and Burns, P.C. (2011) Hydrothermal Allendeite (Sc4Zr3O12) and (Mo, syntheses and structures of the uranyl tellurates Ru,Fe), two new minerals from an ultrarefractory AgUO2(HTeO5) and Pb2UO2(TeO6). Journal of inclusion from the Allende meteorite. American Solid State Chemistry, 184, 401–404. Mineralogist, 99, 654–666. Lippmaa, E., Mägi, M., Samosan, A., Engelhardt, G. Mahlmeister, D. and Irran, E. (2012) Synthesis and crystal and Grimmer, A.-R. (1980) Structural studies of structure of the new telluric acid adduct (RbCl)3 ·Te 29 silicates by solid-state high resolution Si NMR. (OH)6. Zeitschrift für Naturforschung, B: Chemical Journal of the American Chemical Society, 102, Sciences, 67,1–4. 4889–4893. Mandarino, J.A., Williams, S.J. and Mitchell, R.S. (1963) Litaiem, H., Dammak, M., Mhiri, T. and Cousson, A. Denningite, a new tellurite mineral from Moctezuma, (2005) Structural, conductivity and dielectric studies Sonora, Mexico. The Canadian Mineralogist, 7, in (NH4)2SeO4·(Te(OH)6). Journal of Alloys and 443–452. Compounds, 396,34–39. Marezio, M. and Remeika, J.P.(1967) Bond lengths in the Liu, Y., Liu, S.X., Cao, R., Ji, H.M., Zhang, S. and Ren, Y. α-Ga2O3 structure and the high-pressure phase of 46 (2008) Hydrothermal assembly and luminescence Ga2–xFexO3. Journal of Chemical Physics, , property of lanthanide-containing Anderson polyox- 1862–1865. ometalates. Journal of Solid State Chemistry, 181, Margison, S.M., Grice, J.D. and Groat, L.A. (1997) The – 2+ 2237 2242. crystal structure of leisingite, (Cu ,Mg,Zn)2(Mg,Fe) 6+ Locock, A.J. and Burns, P.C. (2004) Revised Tl(I)–O Te O6 ·6H2O. The Canadian Mineralogist, 35, bond valence parameters and the structures of thallous 759–763.

535 A. G. CHRISTY ET AL.

Marrot, J. and Savariault, J.M. (1996) Tricesium ditellur- Lu). Zeitschrift für Naturforschung, B: Chemical ium tetravanadium chloride tetradecaoxide. Acta Sciences, 60, 720–726. C52 – Crystallographica, , 2129 2132. Meier, S.F. and Schleid, T. (2006a)Ho11ClTe16O48: Ein Marsh, R.E. (1988) The structure of Te(OH)6 ·Na3P3O9 · extrem chlorarmes Chlorid-Oxotellurat(IV) des drei- K3P3O9. Acta Crystallographica, C44, 774–774. wertigen Holmiums. Zeitschrift für anorganische und Martinez-Carrera, S., Sanz, J., Pico, C., Gaitan, M., Jerez, allgemeine Chemie, 632, 1759–1767. A. and Veiga, M.L. (1987) Mixed oxides of the system Meier, S.F. and Schleid, T. (2006b)Na2Te 2O7: Ein V IV M Te O2 (M = Nb,Ta,Sb); II. Crystal structure of Natrium-Oxoditellurat (VI) mit eckenverknüpften 6− Ta2Te 2O9. Materials Research Bulletin, 22, [TeO6] -Oktaedern. Zeitschrift für anorganische 1405–1412. und allgemeine Chemie, 632, 2150–2150. Martinez-Lope, M.J., Retuerto, M., Alonso, J.A., Meier, S.F.,Höss, P.and Schleid, T.(2009) Dy2Te 3O9: The Sanchez-Benitez, J. and Fernandez-Diaz, M.T. first representative of lanthanoid(III)-oxotellurates(IV) (2011) High-pressure synthesis and neutron diffraction with composition M2Te 3O9. Zeitschrift für anorga- investigation of the crystallographic and magnetic nische und allgemeine Chemie, 635, 768–775. structure of TeNiO3 perovskite. Dalton Transactions, Meisel, K. (1939) The crystal structure of 40, 4599–4604. phosphides. Zeitschrift für anorganische und allge- Masse, R., Guitel, J.C. and Trodjman, I. (1980) meine Chemie, 240, 300–312. Preparation chimique et structure cristalline des tell- Mellini, M. and Merlino, S. (1981) Versiliaite and urites de sodium et d’argent: Na2TeO 3,Ag2TeO 3. apuanite: derivative structures related to schafarzikite. Materials Research Bulletin, 15, 431–436. American Mineralogist, 64, 1235–1242. Matzat, E. (1968) Die Kristallstruktur eines unbekannten Menzer, G. (1931) The crystal structure of eulytine. zeolithartigen Telluritminerals, (Zn,Fe)2(TeO3)3Nax Zeitschrift für Kristallographie, 78, 136–163. H2–x · y(H2O). Tschermaks mineralogische und petro- Mercurio, D., Champarnaud-Mesjard, J.C., Gouby, I. and 12 – graphische Mitteilungen, , 108 117. Frit, B. (1998) On the crystal structure of Bi2Te 2O7. Mayer, H. and Pupp, G. (1977) Synthese und European Journal of Solid State and Inorganic Kristallstruktur von Te8O10(PO4)4. Zeitschrift für Chemistry, 35,49–65. Kristallographie, 145, 321–333. Mercurio, D., El Farissi, M., Frit, B. and Goursat, P. Mayer, H. and Weil, M. (2003) Synthese und (1983) Étude structurale et densification d’un nouveau Kristallstruktur von Te3O3(PO4)2, einer Verbindung materiau piézoélectrique: Bi2TeO 5. Materials mit fünffach koordiniertem Tellur (IV). Zeitschrift für Chemistry and Physics, 9, 467–476. 629 anorganische und allgemeine Chemie, , Merlino, S. (1983) Okenite, Ca10Si18O46 · 18H2O, the 1068–1072. first example of a chain and sheet silicate. American McDonough, W.F. and Sun, S.-S. (1995) The composition Mineralogist, 68, 614–622. of the Earth. Chemical Geology, 120, 223–254. Meunier, G. and Galy, J. (1971) Sur une déformation Meagher, E.P. and Lager, G.A. (1979) Polyhedral inédité du réseau de type fluorine. Structure cristalline thermal expansion in the TiO2 polymorphs; refine- des phases MTe 3O8 (M = Ti, Sn, Hf, Zr). Acta ment of the crystal structures of rutile and brookite at Crystallographica, B27, 602–608. high temperature. The Canadian Mineralogist, Meunier, G., Darriet, J. and Galy, J. (1972) L’oxyde 17 – ̀ ,7785. double TeVO4. I. Synthese et polymorphisme, struc- Meier, S.F. and Schleid, T. (2002) Synthese und ture cristalline de α-TeVO4. Journal of Solid State Kristallstruktur des (III)-chlorid- oxotellur- Chemistry, 5, 314–320. ats(IV) HoClTeO3. Zeitschrift für anorganische und Meunier, G., Darriet, J. and Galy, J. (1973) L’oxyde 628 – allgemeine Chemie, , 526 528. double TeVO4. II. Structure cristalline de TeVO4-β – Meier, S.F. and Schleid, T. (2003a) HoClTe2O5: ein Relations structurales. Journal of Solid State tellurdioxidreiches Holmium(III)-Chlorid-Oxotellurat Chemistry, 6,67–73. (IV). Zeitschrift für anorganische und allgemeine Meunier, G., Frit, B. and Galy, J. (1976) Cr2Te 4O11: une 629 – Chemie, , 1575 1580. structure à anions complexes (Cr2O10)14. Acta Meier, S.F. and Schleid, T. (2003b) Synthesis and crystal Crystallographica, B32, 175–180. structure of Gd2TeO 6. Journal of Solid State Mikhaylov, A.A., Mel’nik, E.A., Churakov, A.V., Chemistry, 171, 408–411. Novotortsev, V.M., Howard, J.A.K., Sladkevich, S., Meier, S.F. and Schleid, T. (2004) Oxotellurate(IV) Gun, J., Bharathi, S., Lev, O.and Prikhodchenko, P.V. der Lanthanide: I. Die isotype Reihe M2Te 4O11 (2011) Synthesis, crystal structure, and characterization (M = La-Nd, Sm-Yb). Zeitschrift für Naturforschung, of alkali metal hydroxoantimonates. Inorganica B: Chemical Sciences, 59, 881–888. Chemica Acta, 378,24–29. Meier, S.F. and Schleid, T. (2005) Oxotellurate(IV) der Miletich, R. (1991) Hydrothermalsynthese und Lanthanide: II. Die isotype Reihe M2Te 5O13 (M = Dy- Kristallstruktur von MnCu(Te2O5)2 – ein Vertreter

536 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

des Denningit-Typs. Österreische Akademie der central Mojave Desert, California, USA. Wissenschaften, Mathematich-Naturwissenschaftliche Mineralogical Magazine, 78, 1325–1340. Klasse, Sitzungsberichte, 128,31–34. Mills, S.J., Kampf, A.R., Christy, A.G., Housley, R.M., Miletich, R. (1993) Copper-substituted manganese- Thorne, B., Chen, Y.-S. and Steele, I.M. (2014b) denningites, Mn(Mn1–xCux)(Te2O5)2 (0 < x < 1): syn- Favreauite, a new selenite mineral from the El Dragón thesis and crystal chemistry. Mineralogy and mine, Bolivia. European Journal of Mineralogy, 26, Petrology, 48, 129–145. 771–781. Miletich, R. (1995a) Crystal chemistry of the Mills, S.J., Dunstan, M.A. and Christy, A.G. (2016) The + microporous tellurite minerals zemannite and first example of the [Te(OH)3] ion in a crystalline 2+ 3+ kinichilite, Mg0.5[Me Fe (TeO3)3] · 4.5H2O, : the structure of Na11H[Te 2+ (Me = Zn; Mn). European Journal of Mineralogy, (OH)3]8[SO4]10(H2O)13. Dalton Transactions (in 7, 509–523. press). Miletich, R. (1995b) The synthetic microporous tellurites Minimol, M.P. and Vidyasagar, K. (2003) Hydrothermal Na2[Me2(TeO3)3]·3H2O(Me = Zn, Co): Crystal synthesis and characterization of new one-dimensional structure, De- and rehydration, and ion exchange tellurates, A2[Te3O8(OH)4]. Indian Journal of properties. Monatshefte für Chemie/Chemical Chemistry, 42, 2244–2249. Monthly, 126, 417–430. Minimol, M.P. and Vidyasagar, K. (2005) Syntheses and Miletich, R. and Pertlik, F. (1998) Crystal structure of structural characterization of new mixed-valent tellur- 6+ 4+ NaGaTe2O6: Aspects of TenOm polyhedral polymer- ium oxides, A4[Te5 Te 3 ]O23 (A = Rb and K). ization in a layer tellurite. Journal of Alloys and Inorganic Chemistry, 44, 9369–9373. Compounds, 268, 107–111. Mitchell, R.H. (2002) Perovskites. Modern and Ancient. Mills, S.J. and Christy, A.G. (2013) Revised values of the Almaz Press, Thunder Bay, Ontario, Canada. 318 pp. bond valence parameters for TeIV–O, TeVI–O and Moret, J., Philippot, E., Maurin, M. and Lindqvist, O. Te IV–Cl. Acta Crystallographica, B69, 145–149. (1974) Structure cristalline de l’acide tetraoxotellurique Mills, S.J., Christy, A.G., Chen, E.C.C. and Raudsepp, M. H2TeO4. Acta Crystallographica, B30,1813–1818. (2009a) Revised values of the bond valence para- Moret, J., Maurin, M. and Philippot, E. (1979) Étude du [6] [3–11] – – ̀ meters for Sb(V)-O and Sb(III)-O. Zeitschrift ternaire NH3 TeO 3 H2O. Synthese et étude cristallo- für Kristallographie, 224, 423–431. chimique de (NH4)2Te 3O8(OH)4. Revue de Chimie Mills, S.J., Hatert, F., Nickel, E.H. and Ferraris, G. Minerale, 16,39–47. (2009b) The standardisation of mineral group Morgenstern Badarau, I. and Michel, A. (1976) Sur hierarchies: application to recent nomenclature l’éxistence d’un oxyhydroxyde double de fer(III) et proposals. European Journal of Mineralogy, 21, d’étain(IV). Journal of Inorganic and Nuclear 1073–1080. Chemistry, 38, 1400–1402. Mills, S.J., Kolitsch, U., Miyawaki, R., Groat, L.A. and Mouron, P., Odier, P. and Choisnet, J. (1985) Titanates de 5+ 6+ Poirier, G. (2009c) Joëlbruggerite, Pb3Zn3(Sb ,Te ) cuivre substitués à structure bixbyite: les composés 5+ As2O13(OH,O), the Sb analog of dugganite, from Cu1–xTi1–xFe2xO3 (0.15 < x < 0.33). Journal of Solid the Black Pine mine, Montana. American State Chemistry, 60,87–94. Mineralogist, 94, 1012–1017. Müller-Buschbaum, H. and Wedel, B. (1996) Zur Mills, S.J., Kampf, A.R., Kolitsch, U., Housley, R.M. and Kristallchemie der Barium-Oxometallat-Tellurite Raudsepp, M. (2010) The crystal chemistry and crystal Ba2Te 2M6O21 (M = Niob und Tantal). Zeitschrift für 6+ structure of kuksite, Pb3Zn3Te P2O14, and a note on Naturforschung, Teil B, 51, 1411–1414. the crystal structure of yafsoanite, (Ca,Pb)3Zn(TeO6)2. Müller-Buschbaum, H. and Wedel, B. (1997) Über die American Mineralogist, 95, 933–938. Kristallchemie der Tellurate Pb3Fe2Te 2O12 und Mills, S.J., Kartashov, P.M., Ma, C., Rossmann, G.R., Pb2CoTeO6. Zeitschrift für Naturforschung, Teil B, Novgorodova, M.I., Kampf, A.R. and Raudsepp, M. 52,35–39. (2011) Yttriaite-(Y): the natural occurrence of Y2O3 Müller-Buschbaum, H. and Wulff, L. (1997) Planare 4+ from the Bol’shaya Pol’ya River, Subpolar Urals, CuO4-Polygone und eine einseitig offene Te O3 Russia. American Mineralogist, 96, 1166–1170. Koordination in SrCuTe2O6. Zeitschrift für Mills, S.J., Christy, A.G., Génin, J.-M.R., Kameda, T. and Naturforschung, B: Chemical Sciences, 52, Colombo, F. (2012) Nomenclature of the hydrotalcite 1341–1344. supergroup: natural layered double hydroxides. Müller-Buschbaum, H. and Wulff, L. (1998) Zur Mineralogical Magazine, 76, 1289–1336. Kristallchemie der Kupfer(II)-Zink-Tellurate Mills, S.J., Kampf, A.R., Christy, A.G., Housley, R.M., Cu5Zn4Te 3O18 und Cu1.5Zn1.5TeO 6, mit einer Notiz Rossman, G.R., Reynolds, R.E. and Marty, J. (2014a) ueber Cu1.5Co1.5TeO 6. Zeitschrift für Naturforschung, Bluebellite and mojaveite, two new minerals from the Teil B, 53,53–57.

537 A. G. CHRISTY ET AL.

Nalbandyan, V.B., Avdeev, M. and Evstigneeva, M.A. Ok, K.M., Zhang, L. and Halasyamani, P.S. (2003) (2013) Crystal structure of Li4ZnTeO6 and revision of Synthesis, characterization and dielectric properties Li3Cu2SbO6. Journal of Solid State Chemistry, 199, of new unidimensional quaternary tellurites: – 62 65. LaTeNbO6,La4Te 6Nb2O23 and La4Te 6Ta2O23. Nawash, J.M., Twamley, B. and Lynn, K.G. (2007) Journal of Solid State Chemistry, 175, 264–271. ZnTe6O13, a new ZnO-TeO2 phase. Acta Ok, K.M., Orzechowski, J. and Halasyamani, P.S. (2004) Crystallographica, C63, i66–i68. Synthesis, structure, and characterization of two new Nguyen, S.D., Kim, S.-H. and Halasyamani, P.S. (2011) layered mixed-metal phosphates, BaTeMO4(PO4) Synthesis, characterization, and structure-property (M =Nb5+ or Ta5+). Inorganic Chemistry, 43,964–968. ’ relationships in two new polar oxides: Zn2(MoO4) O Keeffe, M. and Andersson, S. (1977) Rod packings and A33 (SeO3) and Zn2(MoO4)(TeO3). Inorganic Chemistry, crystal chemistry. Acta Crystallographica, , 50, 5215–5233. 914–923. Nielsen, B.R., Hazell, R.G. and Rasmussen, S.E. (1971) O’Keeffe, M. and Hyde, B.G. (1981) The role of The crystal structure of barium tellurite monohydrate, nonbonded forces in crystals. Pp. 227–254 in: ’ BaTeO3H2O. Acta Chemica Scandinavica, 25, Structure and Bonding in Crystals I, (M. O Keeffe 3037–3042. and A. Navrotsky, editors). Academic Press, Nikiforov, G.B., Kusainova, A.M., Berdonosov, P.S., New York, USA, 327 pp. Dolgikh, V.A. and Lightfoot, P. (1999) The crystal O’Keeffe, M. and Hyde, B.G. (1985) An alternative structure of the new REE-Te oxychlorides: NdTe2O5Cl approach to non-molecular crystal structures with and GdTe2O5Cl. Journal of Solid State Chemistry, emphasis on the arrangements of cations. Structure 146, 473–477. and Bonding, 61,77–144. Noguera, O., Jouin, J., Masson, O., Jancar, B. and O’Keeffe, M. and Hyde, B.G. (1996) Crystal Thomas, P. (2012) Phase formation and crystal Structures. I. Patterns and Symmetry. Mineralogical structure determination in the Y2O3–TeO 2 system Society of America, Washington DC, 453 pp. prepared in an oxygen atmosphere. Journal of the Olmi, F. and Sabelli, C. (1994) Brizziite, NaSbO3, a new European Ceramic Society, 32, 4263–4269. mineral from the Cetine mine (Tuscany, Italy): O’Callaghan, M.P., Powell, A.S., Titman, J.J., Chen, G.Z. description and crystal structure. European Journal and Cussen, E.J. (2008) Switching on fast lithium ion of Mineralogy, 6, 667–672. conductivity in garnets: the structure and transport Olsson, C., Johansson, L.G. and Kazikowski, S. (1988) properties of Li3+xNd3Te 2–xSbxO12. Chemistry of Structure of silver telluryl nitrate, AgTeO2NO3. Acta Materials, 20, 2360–2369. Crystallographica, C44, 427–429. Oh, S.J., Lee, D.W. and Ok, K.M. (2012) PbMSeO6 (M = Oufkir, A., Dutreilh, M., Thomas, P., Champarnaud- Mo and W): New quaternary mixed metal selenites Mesjard, J.C., Marchet, P. and Frit, B. (2001) The with asymmetric cationic coordination environments. crystal structure of PbTe5O11. Materials Research Dalton Transactions, 41, 2995–3000. Bulletin, 36, 693–703. Ok, K.M. and Halasyamani, P.S. (2001) New tellurites: Palenik, R.C., Abboud, K.A. and Palenik, G.J. (2005) syntheses, structures, and characterization of Bond valence sums and structural studies of antimony K2Te 4O9 · 3.2(H2O), KGaTe6O14, and KGaTe2O6 · complexes containing Sb bonded only to O ligands. 1.8(H2O). Chemistry of Materials, 13, 4278–4284. Inorganica chimica acta, 358, 1034–1040. Ok, K.M. and Halasyamani, P.S. (2002a) Synthesis, Papike, J.J. and Zoltai, T. (1967) Ordering of tetrahedral 3+ structure and characterization of a new tellurate: aluminum in prehnite, Ca2(Al,Fe )[AlSi3O10](OH)2. 4 – 52 – NaBiTeO5. Solid State Sciences, , 793 797. American Mineralogist, , 974 984. Ok, K.M. and Halasyamani, P.S. (2002b) Anionic Park, K.T., Terakura, K. and Matsui, Y.(1988) Theoretical templating: synthesis, structure and characterization evidence for a new ultra-high-pressure phase of SiO2. of novel three-dimensional mixed-metal oxychlorides Nature, 336, 670–672. 5+ 5+ Te 4M3O15 ·Cl (M =Nb or Ta ). Inorganic Pavlyuk, V.V., Dmytriv, G.S. and Bodak, O.I. (1993) Chemistry, 41, 3805–3807. Crystal structure of lithium calcium germanide Ok, K.M. and Halasyamani, P.S. (2005) Mixed-metal (LiCa6Ge). Izvestiya Akademii Nauk SSSR, tellurites: synthesis, structure, and characterization of Neorganicheskie Materialy, 29, 727–728. Na1.4Nb3Te 4.9O18 and NaNb3Te 4O16. Inorganic Park, J.-H. and Woodward, P.M. (2000) Synthesis, Chemistry, 44, 3919–3925. structure and optical properties of two new perovs- Ok, K.M. and Halasyamani, P.S. (2006) Synthesis, kites: Ba2Bi2/3TeO 6 and Ba3Bi2TeO 9. International structure, and characterization of a new one-dimen- Journal of Inorganic Materials, 2, 153–166. sional tellurite phosphate, Ba2TeO(PO4)2. Journal of Park, J.-H., Woodward, P.M., Parise, J.B., Lubomirsky, I. Solid State Chemistry, 179, 1345–1350. and Stafsudd, O. (1999) Synthesis, structure and

538 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

dielectric properties of Na2SnTeO6. Materials Pertlik, F. and Zemann, J. (1988b) The crystal structure of Research Society Symposia Proceedings, 547, nabokoite, Cu7TeO 4(SO4)5 · KCl: The first example of 139–144. a Te(IV)O4 pyramid with exactly tetragonal symmetry. Parker, R.L. (1967) Composition of the Earth’s crust. In: Mineralogy and Petrology, 38, 291–298. Data of Geochemistry, 6th edition. U.S. Geological Phatak, R., Krishnan, K., Kulkarni, N.K., Achary, S.N., Survey Professional Paper 440-D, 19 pp. Banerjee, A. and Sali, S.K. (2010) Crystal structure, Pasero, M. and Perchiazzi, N. (1989) Chalcomenite from magnetic and thermal properties of LaFeTeO6. Baccu Locci, Sardinia, Italy: mineral data and Materials Research Bulletin, 45, 1978–1983. structure refinement. Neues Jahrbuch für Philippot, E., Astier, R., Loeksmanto, W., Maurin, M. and Mineralogie, Monatshefte, 1989, 551–556. Moret, J. (1978) Étude cristallochimique d’un tellurate Pauling, L. (1929) The principles determining the (IV) d’indium In2Te 3O9. Revue de Chimie Minerale, structure of complex ionic crystals. Journal of the 15, 283–291. American Chemical Society, 51, 1010–1026. Philippot, E., Benmiloud, L., Maurin, M. and Moret, J. Peacor, D.R. and Buerger, M.J. (1962) The determination (1979a) Pentacoordination de l’atome de tellure (IV) ̀ and refinement of narsarsukite, Na2TiOSi4O10. par les atomes d’oxygenej. Étude cristallochimique IV VI American Mineralogist, 47, 539–556. d’un oxotellurate mixte: NH4[Te Te O5(OH)]. Acta Pekov, I.V., Chukanov, N.V., Zadov, A.E., Roberts, A.C., Crystallographica, B35, 1986–1989. Jensen, M.C., Zubkova, N.V. and Nikischer, A.J. Philippot, E., Maurin, M. and Moret, J. (1979b) Étude (2010) Eurekadumpite, (Cu,Zn)16(TeO3)2(AsO4)3Cl cristallographique du tellurite de sodium a cinq IV (OH)18 ·7H2O, a new hypergene mineral. Zapiski molecules d’eau, Na2Te O3.5H2O. Acta Rossiyskogo Mineralogicheskogo Obshchestva, 139, Crystallographica, B35, 1337–1340. 26–35 [in Russian, English translation: (2011) Pico, C., Castro, A., Veiga, M.L., Gutiérrez-Puebla, E., Geology of Ore Deposits, 53, 575–582]. Monge, M.A. and Ruiz-Valero, C. (1986) Synthesis, Pekov, I.V., Siidra, O.I., Vlasov, E.A., Yapaskurt, V.O., crystal structure, and some physico-chemical proper- Lukina, E.A., Polekhovsky, Y.S. and Apletalin, A.V. ties of Te3SeO8. Journal of Solid State Chemistry, 63, (2015) Ilirneyite, IMA 2015–046. CNMNC 172–178. Newsletter No. 27. Mineralogical Magazine, 79. Pitzschke, D. and Jansen, M. (2007) Hydrothermal Pekov, I.V.,Vlasov, E.A., Zubkova, N.V.,Yapaskurt, V.O., synthesis and crystal structure of AgVMO5 (M = Se, Chukanov, N.V., Belakovskiy, D.I., Lykova, I.S., Te). Zeitschrift für anorganische und allgemeine Apletalin, A.V., Zolotarev, A.A. and Pushcharovsky, Chemie, 633, 1563–1567. 6+ D.Y. (2016) Raisaite, CuMg[Te O4(OH)2]·6H2O, a Pitzschke, D., Curda, J., Cakmak, G. and Jansen, M. – new mineral from Chukotka, Russia. European (2008) Ag4I2SeO4 and Ag3ITeO4 two new silver Journal of Mineralogy, 28, 459–466. solid electrolytes. Zeitschrift für anorganische und Perez, G., Lasserre, F., Moret, J. and Maurin, M. (1976) allgemeine Chemie, 634, 1071–1076. Structure cristalline des hydroxytellurites de nickel et Platte, C. and Trömel, M. (1981) Nickelditellurat (IV): de cobalt. Journal of Solid State Chemistry, 17, Sauerstoffkoordinationszahl Fünf am vierwertigen 143–149. Tellur. Acta Crystallographica, B37, 1276–1278. Pertlik, F. (1972a) Die Kristallstruktur von Fe2Te 4O11. Podlahova, J., Loub, J., Pechar, F. and Petricek, V. (1984) Tschermaks mineralogische und petrographische Structure of the adduct of orthotelluric acid and 18 – Mitteilungen, ,39 55. potassium iodate, Te(OH)6 · KIO3. Acta Pertlik, F. (1972b) Der Strukturtyp von Emmonsit, Crystallographica, C40, 1999–2001. {Fe2[TeO3]3 ·H2O} · xH2O(x =0−1). Tschermaks Pollitt, S. and Weil, M. (2014) Polymorphism of H2SeO3, mineralogische und petrographische Mitteilungen, NaHSeO4 and Na5H3(SeO4)4(H2O)2, and re- 18, 157–168. refinement of the crystal structure of Te2O4(OH)2. Pertlik, F. (1987) Dimorphism of hydrothermal synthe- Zeitschrift für anorganische und allgemeine Chemie, sized copper tellurite CuTeO3: The structure of a doi: 10.1002/zaac.201400068. monoclinic representative. Journal of Solid State Popova, V.I., Popov, N.S., Rudashevskiy, S.F., Polyakov, Chemistry, 71, 291–295. V.O. and Bushmakin, A.F. (1987) Nabokoite 3+ 3+ Pertlik, F. and Gieren, A. (1977) Verfeinerung der Cu7TeO 4(SO4)5 · KCl and atlasovite Cu6Fe Bi Kristallstruktur von Mackayite, Fe(OH)[Te2O5]. O4(SO4)5 · KCl. New minerals of volcanic exhalations. Neues Jahrbuch für Mineralogie Monatschefe, 1977, Zapiski Rossiyskogo Mineralogicheskogo Obshchestva, 145–154. 116, 358–367 [in Russian with English abstract]. Pertlik, F. and Zemann, J. (1988a) Die Kristallstruktur von Porter, Y. and Halasyamani, P.S. (2003) Cu7(OH)6(TeO3)2(SO4)2. Monatshefte für Chemie/ Syntheses, structures and characterization of new Chemical Monthly, 119,311–317. lead(II)-tellurium(IV)-oxide halides: Pb3Te 2O6X2 and

539 A. G. CHRISTY ET AL.

Pb3TeO 4X2 (X = Cl or Br). Inorganic Chemistry, 42, Robl, C. and Frost, M. (1993d)Na6(TeMo6O24) · 22H2O 205–209. – a layered heteropoly compound with the chain-like 3n+ Porter, Y., Bhuvanesh, N.S.P. and Halasyamani, P.S. polycation (Na3(H2O)11)n . Zeitschrift für (2001) Synthesis and characterization of non-centro- Naturforschung, B: Chemical Sciences, 48, 404–408. 40 symmetric TeSeO4. Inorganic Chemistry, , Robl, C. and Frost, M. (1993e) Alkalimolybdotellurate: 1172–1175. Darstellung und Kristallstruktur von Pospelov, A.A., Nalbandyan, V.B., Serikova, E.I., Rb6(TeMo6O24) · 10H2O und Rb6(TeMo6O24)·Te Medvedev, B.S., Evstigneeva, M.A., Ni, E.V. and (OH)6 ·6H2O eine Tellursäure- reiche Lukov, V.V.(2011) Crystal structure and properties of a Einschlussverbindung. Zeitschrift für anorganische 619 – new mixed-valence compound LiMn2TeO 6 and the und allgemeine Chemie, , 1834 1840. survey of the LiMM′XO6 family (X = Sb or Te). Solid Rodewald, U.C., Hoffmann, R.D., Wu, Z. and Pöttgen, R. State Sciences, 13, 1931–1937. (2006) Structure refinement of AuSn2. Zeitschrift für Post, J.E., Bish, D.L. and Heaney, P.J.(2007) Synchrotron Naturforschung B: Chemical Sciences, 61, 108–110. powder X-ray diffraction study of the structure and Rossell, H.J., Leblanc, M., Ferey, G., Bevan, D.J.M., dehydration behavior of sepiolite. American Simpson, D.J. and Taylor, M.R. (1992) On the crystal Mineralogist, 92,91–97. structure of Bi2Te 4O11. Australian Journal of Prior, T.J., Couper, V.J. and Battle, P.D. (2005) Structural Chemistry, 45, 1415–1425. chemistry of the cation-ordered perovskites Rozier, P., Vendier, L. and Galy, J. (2002) KVTeO5 and a Sr2CaMo1–xTexO6 (0 ≤ x ≤ 1). Journal of Solid State redetermination of the Na homologue. Acta Chemistry, 178, 153–157. Crystallographica, C58,i111–i113. Qurashi, M.M. and Barnes, W.H. (1953) The structure of Rumsey, M.S., Welch, M.D., Mo, F., Kleppe, A.K., Spratt, pucherite, BiVO4. American Mineralogist, 38, J., Kampf, A.R. and Raanes, M.P. (2016) Millsite, 489–500. IMA 2015-086. CNMNC Newsletter No. 29, February Ra, H.-S., Ok, K.M. and Halasyamani, P.S. (2003) 2016, page 201; Mineralogical Magazine, 80,199–205. Combining second-order Jahn-Teller distorted Saalfeld, H. and Wedde, M. (1974) Refinement of the cations to create highly efficient SHG materials: crystal structure of gibbsite, Al(OH)3. Zeitschrift für synthesis, characterisation and NLO properties of Kristallographie, 139, 129–135. 6+ 6+ BaTeM2O9 (M =Mo or W ). Journal of the Sabelli, C. (1987) Structure refinement of elpasolite from American Chemical Society, 125, 7764–7765. Cetine mine, Tuscany, Italy. Neues Jahrbuch für Radtke, A.S., Dickson, F.W. and Slack, J.F. (1978) Mineralogie, Monatshefte, 1987, 481–487. Occurrence and formation of avicennite, Tl2O3,asa Schmidt, K.J., Schrobilgen, G.J. and Sawyer, J.F. (1986) secondary mineral at Carlin gold deposit, Nevada. Hexasodium hexatungstotellurate (VI) 22-hydrate. Journal of Research of the United States Geological Acta Crystallographica, C42, 1115–1118. Survey, 6, 241–246. Schuelke, U., Averbuch-Pouchot, M.T. and Durif, A. Raman, S. (1964) Crystal Structure of KTeO(OH)5·H2O. (1993) Chemical preparation and crystal structure of Inorganic Chemistry, 3, 634–638. an adduct between potassium cyclooctaphosphate and Rastsvetaeva, R.K., Rekhlova, O.Yu, Andrianov, V.I. and telluric acid: Te(OH)6 ·K8P8O24 ·2H2O. Zeitschrift Malinovskii, Yu.A. (1991) Crystal structure of hsian- für Kristallographie, 204, 143–152. ghualite. Doklady Akademii Nauk SSSR, 316, Schulz, H. and Bayer, G. (1971) Structure determination – 624 628. of Mg3TeO 6. Acta Crystallographica, B27, 815–821. Reimann, C. and de Caritat, P. (1998) Chemical Elements Sciau, P., Lapasset, J. and Moret, J. (1986) Structure de la in the Environment. Factsheets for the geochemist and phase quadratique de PbTeO3. Acta environmental scientist. Springer-Verlag, Berlin, 398 pp. Crystallographica, C42, 1688–1690. Robl, C. and Frost, M. (1993a) Water-rich molybdotellu- Sedello, O. and Müller Buschbaum, H. (1996) Synthese rates: preparation and crystal structure of und Kristallstruktur des Barium-Kupfer-Tellurit Li6(TeMo6O24) · 18H2O and Li6(TeMo6O24)·Te Tellurats BaCu(TeO3)(TeO4). Zeitschrift für (OH)6 · 18H2O. Zeitschrift für anorganische und Naturforschung, B: Chemical Sciences, 51, 465–468. allgemeine Chemie, 619, 1137–1146. Semenova, T.F., Rozhdestvenskaya, I.V.,Filatov, S.K. and Robl, C. and Frost, M. (1993b) On the proton-acceptor Vergasova, L.P. (1992) Crystal structure and physical properties of Na4(NH4)2(TeMo6O24) · 16H2O. properties of sophiite, Zn2(SeO3)Cl2, a new mineral. Zeitschrift für anorganische und allgemeine Chemie, Mineralogical Magazine, 56, 241–245. 619, 1132–1136. Shan, Y.J., Yoshioka, Y., Wakeshima, M., Tezuka, K. and Robl, C. and Frost, M. (1993c)Cs6(TeMo6O24) · 2Te Imoto, H. (2014) Synthesis, structure, and magentic (OH)6 ·4H2O – eine Tellursäure- reiche properties of the novel sodium cobalt tellurate Einschlussverbindung. Zeitschrift für anorganische Na5Co15.5Te 6O36. Journal of Solid State Chemistry, und allgemeine Chemie, 619, 1624–1628. 211,63–68.

540 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

Shen, Y.-L. and Mao, J.-G. (2005) Synthesis, crystal Stöger, B., Weil, M. and Zobetz, E. (2010) SrTeO6 and structures, and properties of six new lanthanide(III) BaTeO6: Double perovskites with pronounced super- transition metal tellurium(IV) oxyhalides with structures. Zeitschrift für Kristallographie – three types of structures. Inorganic Chemistry, 44, Crystalline Materials, 225, 125–138. 5328–5335. Stöger, B., Weil, M., Baran, E.J., Gonzalez Baro, A.C., Shen, Y.-L.,Jiang, H.-L., Xu, J., Mao, J.-G. and Cheah, K. Malo, S., Rueff, J.M., Petit, S., Lepetit, M.B., Raveau, W. (2005) Luminescent lanthanide selenites and B. and Barrier, N. (2011a) The dehydration of – tellurites decorated by MoO4 tetrahedra or MoO6 SrTeO3(H2O) a topotactic reaction for preparation octahedra: Nd2MoSe2O10,Gd2MoSe3O12, of the new metastable strontium oxotellurate(IV) phase La2MoTe3O12, and Nd2MoTe3O12. Inorganic ε-Sr(TeO3). Dalton Transactions, 40,5538–5548. Chemistry, 44, 9314–9321. Stöger, B., Weil, M., Silich, K.A., Olenev, A.V., Shirkhanlou, M. and Weil, M. (2013) The Mg member of Berdonosov, P.S. and Dolgikh, V.A. (2011b) the isotypic series MTe 6O13. Acta Crystallographica, Synthesis and structural characterization of new E69 , i18. phases in the cubic M3Te 2O6X2 (M = Sr, Ba; X = Cl, Sidey, V. (2009) Alternative presentation of the Brown- Br) structure family. Zeitschrift für anorganische und Wu bond-valence parameters for some s2 cation/ allgemeine Chemie, 637, 1322–1329. O2– ion pairs. Acta Crystallographica, B65, Strunz, H. and Contag, B. (1960) Hexahydroxostannate 99–101. Fe, Mn, Co, Mg, Ca (Sn(OH)6) und deren Sivakumar, T., Ok, K.M. and Halasyamani, P.S. (2006) Kristallstruktur. Acta Crystallographica, 13, 601–603. Synthesis, structure, and characterization of novel two- Sullens, T.A. and Albrecht Schmitt, T.E. (2005) Structure and three-dimensional vanadates: Ba2.5(VO2)3(SeO3)4. and properties of the thorium vanadyl tellurate Th H2O and La(VO2)2(TeO6).3H2O. Inorganic Chemistry, (VO2)2(TeO6)(H2O)2. Inorganic Chemistry, 44, 45, 3602–3605. 2282–2286. Smith, J.V. (1953) Reexamination of the crystal structure Swainson, I.P. and Hammond, R.P. (2003) Hydrogen 38 – of melilite. American Mineralogist, , 643 661. bonding in ikaite, CaCO3 ·6H2O. Mineralogical Sokolov, M.N., Peresypkina, E.V.,Kalinina, I.V.,Virovets, Magazine, 67, 555–562. A.V., Korenev, V.S. and Fedin, V.P. (2010) New Swihart, G.H., Sen Gupta, P.K., Schlemper, E.O., Back, cluster-polyoxometalate hybrids derived from the M.E. and Gaines, R.V. (1993) The crystal structure of incorporation of {Mo3S4} and {Mo3CuS4} units into moctezumite [PbUO2](TeO3)2. American {EW15} cores (E = As(III), Sb(III), Te(IV)). European Mineralogist, 78, 835–839. Journal of Inorganic Chemistry, 2010, 5446–5454. Tagg, S.L., Huffmann, J.C. and Zwanziger, J.W. (1994) Song, S.Y., Lee, D.W. and Ok, K.M. (2014) Rich Crystal structure and sodium environments in sodium structural chemistry in selenium/tellurium tetratellurite, Na2Te 4O9, and sodium tellurite, oxides: mixed-valent selenite-selenates, Sc2(SeO3)2 Na2TeO 3, by X-ray crystallography and sodium-23 6 – (SeO4)andSc2(TeO3)(SeO3)(SeO4), and ternary tellur- NMR. Chemistry of Materials, , 1884 1889. ite Sc2(TeO3)3. Inorganic Chemistry, 53,7040–7046. Tagg, S.L., Huffmann, J.C. and Zwanziger, J.W. (1997) Spiridonov, E.M. and Tananeyva, O.I. (1982) Crystal structure of sodium ditellurite, Na4Te 4O10. Plumbotellurite, α-PbTeO3, a new mineral. Doklady Acta Chemica Scandinavica, 51,118–121. Akademii Nauk SSSR, 262, 1231–1235. Tait, K.T., DiCecco, V., Cooper, M.A., Ball, N.A. and Staack, M. and Müller-Buschbaum, H. (1997) Hawthorne, F.C. (2014) Backite, Pb2Al(TeO6)Cl, a Dicobaltoarsenat – (CoAsO7)-Baugruppen im new tellurate mineral from the Grand Central mine, Cobaltoxid Tellurat Co6O2(TeO4(CoAsO5)2). Tombstone Hills, Cochise County, Arizona: descrip- Zeitschrift für Naturforschung, Teil B, 52, 643–646. tion and crystal structure. The Canadian Mineralogist, Stöger, B. and Weil, M. (2012) The barium oxotellurate 52, 935–942 (IV) bromides Ba6Te 10O25Br2 and Ba3Te 3O8Br2 with Takagi, R. and Johnsson, M. (2005) Ca2CuTe4O10Cl2,a channel structures. Zeitschrift für anorganische und new synthetic tellurium(IV) oxochloride. Acta allgemeine Chemie, 638, 2150–2157. Crystallographica, C61, i106–i108. Stöger, B. and Weil, M. (2013) The calcium oxotellurate Takagi, R. and Johnsson, M. (2006) Sr2Cu2TeO 6Br2: (IV) nitrates Ca5Te 4O12(NO3)2(H2O)2 and honeycomb layers of copper(II) ions. Acta C62 – Ca6Te 5O15(NO3)2: non-classic order/disorder poly- Crystallographica, , i38 i40. typism and a rigid framework structure. Mineralogy Takagi, R., Johnsson, M., Gnezdilov, V., Kremer, R.K., and Petrology, 107, 257–263. Brenig, W. and Lemmens, P. (2006a) Investigation of Stöger, B., Weil, M., Zobetz, E. and Giester, G. (2009) the oxohalide Cu4Te 5O12Cl4 with weakly coupled Cu Polymorphism of CaTeO3 and solid solutions CaxSr1–x (II) tetrahedra. Physical Review, Serie 3. B – TeO 3. Acta Crystallographica, B65, 167–181. Condensed Matter, 74, 014413-1–014413-8.

541 A. G. CHRISTY ET AL.

Takagi, R., Duc, F.and Johnsson, M. (2006b)Molybdenum Trömel, M., Maetz, J. and Müllner, M. (1977) (VI) tricopper(II) tellurium(IV) heptaoxide dichloride Berylliumtellurat Be4TeO 7. Acta Crystallographica, hemihydrate. Acta Crystallographica, C62,i16–i18. B33, 3959–3961. Takagi,R.Johnsson,M.,Kremer,R.K.andLemmens,P. Trömel, M., Hötzler, F.W., Burckhardt, H.G., Platte, C. (2006c) Crystal structure and magnetic properties of and Muench, E. (1987) Lanthanoidtellurate Ln2TeO 6. the coupled spin dimer compound SrCu2(TeO3)2Cl2. Zeitschrift für anorganische und allgemeine Chemie, Journal of Solid State Chemistry, 179, 3763–3767. 551,95–100. Takagi, R., Torino Hjelmqvist, D. and Johnsson, M. Troyanov, S.I., Tikhomirov, G.A., Znamenkov, K.O. and (2007) The solid solution Co3.6Mg1.4Cl2(TeO3)4. Acta Morozov, I.V. (2000) Crystal structure of Crystallographica, E63, i146–i147. complexes (NO)2(Be(NO3)4) and Be4O(NO3)6. Takagi, R.F., Johnsson, M. and Lidin, S. (2008) Single- Zhurnal Neorganicheskoi Khimii, 45, 1941–1948. crystal x-ray study of Ba2Cu2Te4O11Br2 and its Trudu, A.G. and Knittel, U. (1998) Crystallography, incommensurately modulated superstructure com- mineral chemistry and chemical nomenclature of panion. Chemistry – A European Journal, 14, goldfieldite, the tellurian member of the tetrahedrite 3434–3441. solid-solution series. The Canadian Mineralogist, 36, Takagi, R.F., Hjelmqvist, D.T., Johnsson, M. and Lidin, S. 1115–1137. – (2009) Helical chains of [MO5Cl] octahedra Three Ulku, D. (1967) Untersuchungen zur Kristallstruktur und compounds in the new family AEM2T3O8Cl2 (AE = magnetischen Struktur des Ferberits, FeWO4. Ca, Sr and M = Co, Ni). Solid State Sciences, 11,13–17. Zeitschrift für Kristallographie, 124, 192–219. Tang, Y., He, Z., Guo, W., Zhang, S. and Yang, M. (2014) Untenecker, H. and Hoppe, R. (1986a) Die Syntheses and magnetic properties of new tellurite- Koordinationszahl 5 bei Telluraten: Cs2K2[TeO5]. 124 – sulfate compounds M2(TeO3)(SO4)·H2O(M =Co, Journal of the Less-Common Metals, ,29 40. Mn) with a layer structure showing a distorted Untenecker, H. and Hoppe, R. (1986b) Neues über 53 honeycomb spin-lattice. Inorganic Chemistry, , Oxotellurate: K3Li3(TeO6). Journal of the Less- 5862–5868. Common Metals, 124, 251–262. Tarasov, I.V., Dolgikh, V.A., Aksel’rud, L.G., Untenecker, H. and Hoppe, R. (1986c) Neue Oxotellurate Berdonosov, P.S. and Ponovkin, B.A. (1996) (VI): K4Na2(TeO6). Journal of the Less-Common NdTe2O5Br is a new representative of the Bi3O4Br Metals, 125, 223–231. type structures. Zhurnal Neorganicheskoi Khimii, 41, Untenecker, H. and Hoppe, R. (1987a) Ein neues – 1243 1247. oxotellurat, Na4TeO 5, und eine revision der struktur Taylor, S.R. and McLennan, S.M. (1985) The Continental von Li4TeO 5. Journal of the Less Common Metals, Crust: its Composition and Evolution. An 132,79–92. Examination of the Geochemical Record Preserved Untenecker, H. and Hoppe, R. (1987b) Neue Oxotellurate in Sedimentary Rocks. Blackwell Scientific, Oxford, (VI): KNa5(TeO6). Journal of the Less-Common UK, 312 pp. Metals, 132,93–105. Thomas, P., Jeansannetas, B., Champarnaud-Mesjard, J. Vallar, S. and Goreaud, M. (1997) Crystal structure of a C. and Frit, B. (1996) Crystal structure of a new monoclinic form of TeMo5O16, a two-dimensional IV VI mixed-valence bismuth oxotellurate Bi2Te Te O8. conductor mixed-valence oxide. Journal of Solid State European Journal of Solid State Inorganic Chemistry, Chemistry, 129, 303–307. 33, 637–646. van Bever, A.K. (1935) The crystal structure of calcium 90 Thornber, M.R., Bevan, D.J.M. and Graham, J. (1968) chloride, CaCl2. Zeitschrift fuer Kristallographie, , Mixed oxides of the type MO2 (fluorite) – M2O3. III. 374–376. Crystal structures of the intermediate phases van der Lee, A. and Astier, R. (2007) Structural evolution Zr5Sc2O13 and Zr3Sc4O12. Acta Crystallographica, in iron tellurates. Journal of Solid State Chemistry, B24, 1183–1190. 180, 1243–1249. Thümmel, H.J. and Hoppe, R. (1974) Über die Tellurite Veblen, D.R. and Burnham, C.W. (1978) New biopyr- der Alkalimetalle vom Typ M2TeO 3. Zeitschrift fuer iboles from Chester, Vermont. II. The crystal chem- Naturforschung, Teil B. Anorganische Chemie, istry of jimthompsonite, clinojimthompsonite, and Organische Chemie, 29,28–31. and the amphibole-mica reactions. Tindemans-van Eijndhoven, J.C.M. and Verschoor, G.C. American Mineralogist, 63, 1053–1073. (1974) Redetermination of the crystal structure of Viciu, L., Huang, Q., Morosan, E., Zandbergen, H.W., Cs2AuAuCl6. Materials Research Bulletin, 9, Greenbaum, N.I., McQueen, T. and Cava, R.J. (2007) 1667–1670. Structure and basic magnetic properties of the Trömel, V.M. and Scheller, T. (1976) Die kristallstruktur honeycomb lattice compounds Na2Co2TeO 6 and von Co6Te 5O16. Zeitschrift für anorganische und Na3Co2SbO6. Journal of Solid State Chemistry, 180, allgemeine Chemie, 427, 229–234. 1060–1067.

542 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

von Dreele, R.B., Eyring, L., Bowman, A.L. and Yarnell, Weil, M. (2006a)Mn3TeO 6. Acta Crystallographica, E62, J.L. (1975) Refinement of the crystal structure of i244–i245. Pr7O12 by powder neutron diffraction. Acta Weil, M. (2006b)Zn3TeO 6. Acta Crystallographica, E62, Crystallographica, B31, 971–974. 1246–1247. Walitzi, E.M. (1964) Die Kristallstruktur von Denningit, Weil, M. (2007a) Redetermination of Ag2[TeO2(OH)4]: a (Mn,Ca,Zn)Te2O5. Naturwissenschaften, 51, revised hydrogen-bonding scheme. Acta 334–335. Crystallographica, E63, i77–i79. Walitzi, E.M. (1965) Die Kristallstruktur von Denningit, Weil, M. (2007b) New silver tellurates – the crystal (Mn, Ca, Zn)Te2O5. Ein Beispiel für die Koordination structures of a third modification of Ag2Te 2O6 and of um vierwertiges Tellur. Tschermaks mineralogische Ag4TeO 5. Zeitschrift für anorganische und allgemeine und petrographische Mitteilungen, 10, 241–255. Chemie, 633, 1217–1222. Wang, Z. and Becker, H. (2013) Ratios of S, Se and Te in Weil, M. (2014) Two modifications of (TeO)(HAsO4) and the silicate Earth require a volatile-rich late veneer. its dehydration product (Te3O3)(AsO4)2 – three more Nature, 499, 328–331. examples of tellurium (IV) with a fivefold oxygen Weber, F.A. and Schleid, T. (2000) Pr2Te 2O7:A coordination. Zeitschrift für anorganische und allge- (III) oxide oxotellurate (IV) according meine Chemie, 640, 128–135. to Pr2O(TeO3)2 with pyrochlore-type crystal structure. Weil, M. and Stöger, B. (2007a) Redetermination of Zeitschrift für anorganische und allgemeine Chemie, SrTe3O8 from a hydrothermally grown single crystal. 626, 1285–1287. Acta Crystallographica, E63,i116–i118. Wedel, B. and Müller-Buschbaum, H. (1996) Ueber ein Weil, M. and Stöger, B. (2007b) Digallium(III) tris 2+ Blei-Kupfer-Tellurat PbCu3TeO 7 mit Cu in defor- (tellurate(IV)) trihydrate. Acta Crystallographica, miert tetragonal pyramidaler und tetraedrischer E63, i202–i202. Sauerstoffkoordination. Zeitschrift fuer Weil, M. and Stöger, B. (2008a) NaFe(TeO3)2. Acta Naturforschung, Teil B, 51, 1587–1590. Crystallographica, E64,i3–i3. Wedel, B. and Sugiyama, K. (1999) A new tellurium Weil, M. and Stöger, B. (2008b) A non-twinned compound with the garnet structure: Na3Te2(Fe,Al)3O12. polymorph of CaTe2O5 from a hydrothermally Zeitschrift für Kristallographie, 214, 151–152. grown crystal. Acta Crystallographica, C64,i79–i81. Wedel, B., Sugiyama, K. and Müller-Buschbaum, H. Weil, M. and Stöger, B. (2010) Pb3Te 2O6Br2. Acta (1998) Verknüpfung von (TeO6)6 und (TeO6)3(NiO6)3 Crystallographica, E66,i7–i7. sechsringen durch TeNiO9-Oktaederdoppel in Weller, M.T., Pack, M.J., Binsted, N. and Dann, S.E. Pb3Ni4.5Te 2.5O15. Zeitschrift für Naturforschung B: (1999) The structure of cesium tellurate(VI) by Chemical Sciences, 53, 527–531. combined EXAFS and powder X-ray Diffraction. Weil, M. (2003a) Preparation, thermal behaviour and Journal of Alloys and Compounds, 282,76–78. crystal structure of the basic mercury (II) tetraoxo- Wells, A.F. (1947) Structural Inorganic Chemistry. 1st tellurate (VI), Hg2TeO 5, and redetermination of the edition. Oxford University Press, UK, 344 pp. crystal structure of mercury (II) orthotellurate (VI), Wildner, M. (1993) Zemannite-type selenites – crystal Hg3TeO 6. Zeitschrift für anorganische und allgemeine structures of K2[Co2(SeO3)3]·2H2O and Chemie, 629, 653–657. K2[Ni2(SeO3)3]·2H2O. Mineralogy and Petrology, Weil, M. (2003b) Dimorphism in mercury(II) tellurite(IV) 48, 215–225. – tellurate(VI): preparation and crystal structures of Wilk, P., Keller, H.L. and Wimbert, L. (1998) BiTeO3 I alpha- and beta-(Hg2Te 2O7). Zeitschrift für das erste Mitglied eines neuen Strukturtyps. Zeitschrift Kristallographie, 218, 691–698. für Kristallographie, 15,64–64. Weil, M. (2004a) Preparation and crystal structures of the Williams, S.A. (1974) Cesbronite, a new copper tellurite II VI hydrous mercury tellurates Hg (H4Te O6) and from Moctezuma, Sonora. Mineralogical Magazine, I VI VI 39 – Hg2(H4Te O6)(H6Te O6) · 2(H2O). Zeitschrift für , 744 746. anorganische und allgemeine Chemie, 630,1048–1053. Williams, S.A. (1975) Xocometatlite, Cu3TeO 4(OH)4, and Weil, M. (2004b) New phases in the systems Ca-Te-O and , Cu10Zn6(TeO3)(TeO4)2Cl(OH)25 · 27H2O, Cd-Te-O: the calcium tellurite(IV) Ca4Te 5O14 and the two new minerals from Moctezuma, Sonora, cadmium compounds Cd2Te 3O9 and Cd2Te 2O7 with Mexico. Mineralogical Magazine, 40, 221–226. mixed-valent oxotellurium(IV/VI) anions. Solid State Williams, S.A. (1979) Girdite, oboyerite, fairbankite and Sciences, 6,29–37. winstanleyite, four new tellurium minerals Weil, M. (2005a)Ag2Hg2(TeO4)3. Acta from Tombstone, AZ. Mineralogical Magazine, 43, Crystallographica, C61, i103–i105. 453–457. Weil, M. (2005b) Redetermination of MgTe2O5. Acta Wisser, T. and Hoppe, R. (1989) Neues über Oxotellurate Crystallographica, E61, i237–i239. (VI) der Alkalimetalle Zur Existenz und Konstitution

543 A. G. CHRISTY ET AL.

2+ 2+ 2+ von Li6TeO 6. Zeitschrift für anorganische und allge- (A =Sr ,Ba ,orPb ). Inorganic Chemistry, 50, meine Chemie, 573, 133–142. 8663–8670. Wisser, T. and Hoppe, R. (1990a) Ein Oxotellurat (VI) Yeon, J.H., Kim, S.-H. and Halasyamani, P.S. (2011b) neuen Typs: Rb6[TeO5][TeO4]. Zeitschrift für anorga- Crystal structure of a new quinternary oxide: 584 – nische und allgemeine Chemie, , 105 113. NaTl3Cu4Te 2O12. Journal of Chemical Wisser, T. and Hoppe, R. (1990b) Das erste quinquinäre Crystallography, 41, 328–331. Oxotellurat (VI): K3Na2LiTeO6. Zeitschrift für anor- Yeon, J., Kim, S.-H., Green, M.A., Bhatti, K.P., Leighton, ganische und allgemeine Chemie, 586, 125–135. C. and Halasyamani, P.S. (2012a) Syntheses, crystal Woodward, J.D. and Albrecht-Schmitt, T.E. (2005) structures, and characterization of two new Tl+-Cu2+- 6+ Molten salt synthesis and structure of the new Te oxides: Tl4CuTeO6 and Tl6CuTe2O10. Journal of 196 – layered uranyl tellurite, K4((UO2)5(TeO3)2O5). Solid State Chemistry, , 607 613. Journal of Solid State Chemistry, 178, 2922–2926. Yeon, J., Kim, S.-H., Nguyen, S.D., Lee, H. and Woodward, J.D., Almond, P.M. and Albrecht Schmitt, T.E. Halasyamani, P.S. (2012b) Two new noncentrosym- (2004) Synthesis and crystal structures of the layered metric (NCS) polar oxides: syntheses, characterization, uranyl tellurites A2((UO2)3(TeO3)2O2)(A = K, Rb, Cs). and structure-property relationships in BaMTe 2O7 Journal of Solid State Chemistry, 177,3971–3976. (M =Mg2+ or Zn2+). Inorganic Chemistry, 51, Woodward, P.M., Sleight, A.W., Du, L.-S. and Grey, C.P. 2662–2668. (1999) Structural studies and order-disorder phenom- Yin, Y. and Keszler, D.A. (1992) Crystal chemistry of enon in a series of new quaternary tellurates of the type colquiriite-type fluorides. Chemistry of Materials, 4, 2+ 4+ 6+ 1+ 4+ 6+ – A M Te O6 and A2 M Te O6. Journal of Solid 645 648. State Chemistry, 147,99–116. Yu, Y., Ok, K.M. and Halasyamani, P.S. (2004) Synthesis Wulff, L. and Müller-Buschbaum, H. (1998) Isolierte and characterization of two novel mixed metal trigonale SrO6 – Prismen verknüpfen Kagome-Netze tellurates: KGaTeO5 ·H2O and K3GaTe2O8(OH)2 · 2004 – im Strontium-Manganat(IV)-Tellurat(VI): SrMnTeO6. H2O. Dalton Transactions, , 392 396. Zeitschrift für Naturforschung, B53, 283–286. Yun, G., Hwang, Y., Yun, H., Do, J. And Jacobson, A.J. Wulff, L., Wedel, B. and Müller-Buschbaum, H. (1998) (2010) Avanadium tellurate, (NH4)2[VO2]2[TeO4(OH)2], 2+ Zur Kristallchemie von Telluraten mit Mn im containing two edge-shared square-pyramidal VO5 kationischen und anionischen Teil der groups. Inorganic Chemistry, 49,229–233. Kristallstruktur: (Mn2.4Cu0.6)TeO6,Ba2MnTeO6 und Zachariasen, W.(1928) On the crystal structure of bixbyite Pb(Mn0.5Te 0.5)O3. Zeitschrift für Naturforschung, and of synthetic Mn2O3. Zeitschrift für B53,49–52. Kristallographie, 67, 455–464. Xiao, D., Wang, S., Wang, E., Hou, Y., Li, Y., Hu, C. and Xu, Zalkin, A. and Templeton, D.H. (1964) X-ray diffraction L. (2003) Hydrothermal synthesis and crystal structure of refinement of the calcium tungstate structure. Journal 40 – a three-dimensional vanadium tellurite V4Te 4O18. of Chemical Physics, , 501 504. Journal of Solid State Chemistry, 176, 159–164. Zavodnik, V.E., Ivanov, S.A. and Stash, A.I. (2007) The Xu, J., Assoud, A., Soheilnia, N., Derakhshan, S., alpha-phase of SrTeO3 at 295 K. Acta Cuthbert, H.L., Greedan, J.E., Myungwhan, W. and Crystallographica, E63, i75–i76. Kleinke, H. (2005) Synthesis, structure, and magnetic Zavodnik, V.E.,Ivanov, S.A. and Stash, A.I. (2008) alpha- properties of the layered copper(II) oxide Lead tellurite from single-crystal data. Acta Na2Cu2TeO 6. Inorganic Chemistry, 44, 5042–5046. Crystallographica, E64, i16–i16. Yablokova, S.V., Dubakina, L.S. Dmitrik, A.L. and Zhang, D. and Johnsson, M. (2008) Zn2(TeO3)Br2. Acta Sokolova, G.V.(1975) Kuranakhite – a new supergene Crystallographica, E64, i26–i26. tellurium mineral. Zapiski Rossiyskogo Zhang, D. and Johnsson, M. (2009) Nickel vanadium 104 – Mineralogicheskogo Obshchestva, , 310 313. tellurium oxide, NiV2Te 2O10. Acta Crystallographica, Yamanaka, T., Uchida, A. and Nakamoto, Y. (2013) C65,i9–i10. Structural transition of post-spinel phases CaMn2O4, Zhang, D., Johnsson, M., Berger, H., Kremer, R.K., CaFe2O4 and CaTi2O4 under high pressures up to Wulferding, D. and Lemmens, P. (2009a) Separation 80 GPa. American Mineralogist, 93, 1874–1881. of the oxide and halide part in the oxohalide Yan, X.H., Mo, S., Ju, Z.H., Wu, J.G. and Yao, K.L. Fe3Te 3O10Cl due to high Lewis acidity of the (2008) Synthesis and structure of a series of Anderson- cations. Inorganic Chemistry, 48, 6599–6603. Evans type heteropolymolybdates: (Ln Zhang, D., Johnsson, M. and Kremer, R.K. (2010a)Two (H2O)n)2(TeMo6O24) · 6(H2O). Synthesis and new layered oxohalides in the system Cu-Yb-Te-O-Cl. Reactivity in Inorganic, Metal-Organic and Nano- Solid State Sciences, 12, 536–540. Metal Chemistry, 38, 529–533. Zhang, D., Kremer, R.K., Lemmens, P., Choi, K.-Y., Liu, Yeon, J., Kim, S.-H., Hayward, M.A. and Halasyamani, P. J., Wnagbo, M., Berger, H., Skourski, Yu. and S. (2011a) “A” cation polarity control in ACuTe2O7 Johnsson, M. (2011a) Crystal structure and magnetic

544 THE STRUCTURAL ARCHITECTURE OF TELLURIUM OXYCOMPOUNDS

properties of two new antiferromagnetic spin dimer the Ag(I)-Mo(VI)/W(VI)-Te(IV)-O systems. Dalton compounds: FeTe3O7X (X = Cl, Br). Inorganic Transactions, 2009, 5747–5754. Chemistry, 50, 12877–12885. Zikmund, Z. (1967) On the crystal structure of ortho- Zhang, J.J., Zhang, Z.H., Zhang, W.G., Zheng, Q.X., Sun, rhombic K2TeO 3(OH)2(H2O)2.5. Czechoslovak Y.X., Zhang, C.Q. and Tao, X.T. (2011b) Journal of Physics, 17, 196–198. Polymorphism of BaTeMo2O9: a new polar poly- Zilber, R., Durif, A. and Averbuch-Pouchot, M.T. (1980a) morph and the phase transformation. Chemistry of Structure of tellurate: Te(OH)6K2SO4. Materials, 23, 3752–3761. Acta Crystallographica, B36, 2743–2745. Zhang, J.J., Zhang, Z.H., Sun, Y.X., Zhang, C.Q., Zhang, Zilber, R., Tordjman, I. and Guitel, J.C. (1980b) Structure S.J., Liu, Y. and Tao, X.T. (2012a) MgTeMoO6:A of sodium sulfate tellurate. Acta Crystallographica, neutral layered material showing strong second- B36, 2741–2743. harmonic generation. Journal of Materials Zilber, R., Durif, A. and Averbuch-Pouchot, M.T. (1981) Chemistry, 19, 9921–9927. Structure of ammonium sulfate tellurate Te(OH)6 · Zhang,S.,Jiang,H.,Sun,C.F.andMao,J.G.(2009b) (NH4)2SO4. Acta Crystallographica, B37, 650–652. Syntheses, crystal structures, and properties of five Zilber, R., Durif, A. and Averbuch-Pouchot, M.T. (1982) new transition metal molybdenum(VI) selenites Structure of thallium sulfate tellurate Te(OH)6 · 48 B38 – and tellurites. Inorganic Chemistry, , Tl2SO4. Acta Crystallographica, , 1554 1556. 11809–11820. Zimmermann, I., Kremer, R.K. and Johnsson, M. (2011) Zhang, S., Hu, C., Sun, C.F. and Mao, J.G. (2010b) crystal structure and magnetic properties of the open Syntheses and crystal structures of a series of alkaline framework compound Co3Te 2O2(PO4)2(OH)4. earth vanadium selenites and tellurites. Inorganic Journal of Solid State Chemistry, 184, 3080–3084. Chemistry, 49, 11627–11636. Zitzer, S. and Schleid, T. (2009) Ein neues Selten-Erd- Zhang, S., Hu, C. and Mao, J. (2011c) New mixed metal Metall(III)-Oxidchlorid-Oxotellurat(IV): 2+ selenites and tellurites containing Pd ions in a square Nd5O4Cl3[TeO3]2. Zeitschrift für Naturforschung, B: planar geometry. Dalton Transactions, 41, Chemical Sciences, 64, 197–203. 2011–2017. Zitzer, S. and Schleid, T. (2010) The first alkali-metal Zhang, S., Hu, C., Li, P., Jiang, H. and Mao, J. (2012b) lanthanoid(III) iodide oxotellurate(IV): Syntheses, crystal structures and properties of a new Na2Lu3I3[TeO4]3. Zeitschrift für anorganische und lead(II) or bismuth(III) selenites and tellurite. Dalton allgemeine Chemie, 636, 1050–1055. Transactions, 41, 9532–9542. Zoltai, T. (1960) Classification of silicates and other Zhou, Y., Hu, C., Hu, T., Kong, F. and Mao, J.G. (2009) minerals with tetrahedral structures. American Explorations of new second-order NLO materials in Mineralogist, 45, 960–973.

545