Z. Naturforsch. 2015; 70(8)b: 541–546

Muhammad Nawaz Tahir, Anvarhusein A. Isab, Fozia Afzal, Kashif Raza, Shah Muhammad, Muhammad Hanif, Sajjad Ahmad, Tahira Gul and Saeed Ahmad* Synthesis and characterization of (I) complexes of thioureas and : crystal structure of polymeric (1,3-diazinane-2-thione) thiocyanato silver(I)

DOI 10.1515/znb-2014-0263 the sulfur coordination to silver(I). The appearance of a Received October 27, 2014; accepted April 2, 2015 band around 2100 cm–1 in the IR and a resonance around 125 ppm in the 13C NMR spectrum indicates the binding of thiocyanate to silver(I). Abstract: Silver(I) complexes of thioureas and thiocy- anate, [(Tu)AgSCN], [(Metu)AgSCN], [(Dmtu)AgSCN], Keywords: silver(I) complexes; spectroscopy; thioureas;

[(Tmtu)(AgSCN)1.5], [(Imt)AgSCN], and [(Diaz)AgSCN] thiocyanate; X-ray structure. (where Tu = thiourea, Metu = N-methylthiourea, Dmtu = N,N′-dimethylthiourea, Tmtu = N,N,N′,N′- tetramethylthiourea, Imt = 1,3-imidazolidine-2-thione, and Diaz = 1,3-diazinane-2-thione), have been prepared 1 Introduction and characterized by elemental analysis, IR and NMR The complexation of thiones towards metal ions such as spectroscopy, and thermal analysis. The crystal structure copper(I) and silver(I) has received considerable impor- of one of them, [(Diaz)Ag(SCN)] (1), was determined by tance in view of their variable bonding modes, structural X-ray crystallography. The crystal structure of 1 shows diversity, and promising biological implications [1–10]. that the complex exists in the form of a chain-like poly- Our interest in these ligands is because of their relevance mer comprising [Ag(μ -Diaz)(μ -SCN)] units. The silver 2 2 to biological systems [3, 4], and consequently, we have atoms are bridged by μ -thione sulfur atoms of Diaz and 2 been investigating the coordination chemistry of > C = S μ -thiocyanate sulfur atoms. Thereby each silver atom 2 ligands with d10 metal ions in an attempt to assess their adopts a distorted tetrahedral coordination environment modes of binding and to study their physical properties comprising four sulfur atoms, two from thione and two [10–18]. Several complexes of thiones with from thiocyanate ligands. An upfield shift in the > C = S have been prepared and characterized using NMR spec- resonance of thiones in 13C NMR and a downfield shift troscopy and X-ray crystallography. These studies have in the N–H resonance in 1H NMR are consistent with shown that some of these compounds exist as mononu- clear species LAgCN, while others exist in the ionic form + – *Corresponding author: Saeed Ahmad, Department of Chemistry, [AgL2] [Ag(CN)2] [7, 11–13]. However, the reports about University of Engineering and Technology, Lahore 54890, Pakistan, the coordination of thiones with silver thiocyanate are Tel.: +92-333-5248570, E-mail: [email protected] still limited [19–21]. Therefore, in the present paper, we Muhammad Nawaz Tahir: Department of Physics, University of report the synthesis of some new [(thioamide)(AgSCN) ] Sargodha, Sargodha, Pakistan n Anvarhusein A. Isab: Department of Chemistry, King Fahd University (n = 1 or 1.5) complexes, which have been characterized of Petroleum and Minerals, Dhahran 31261, Saudi Arabia by IR, 1H and 13C NMR spectroscopy, and thermal analysis. Fozia Afzal, Kashif Raza, Muhammad Hanif and Tahira Gul: The crystal structure of one of these compounds, [(Diaz) Department of Chemistry, University of Engineering and Technology, Ag(SCN)], is also presented. The structure of the Imt Lahore 54890, Pakistan complex was also determined, but it was found to be the Shah Muhammad: Department of Chemical Engineering, University of Engineering and Technology, Lahore 54890, Pakistan same as an already reported one, [(Imt)2Ag(SCN)] [19, 20]. Sajjad Ahmad: Department of Chemistry, Quaid-i-Azam University, The structures of thioamides used in this study are shown Islamabad, Pakistan in Scheme 1. 542 M.N. Tahir et al.: Synthesis and characterization of silver(I) complexes of thioureas and thiocyanate

CH CH3 CH3 CH3 CH3 3

H N NH H N NH HN NH N N 2 2 2 CH H3C 3

S S S S

Thiourea (Tu) N-Methylthiourea (Metu) N,NÄ-Dimethylthiourea (Dmtu) N,NNÄ NÄ-Tetramethylthiourea (Tmtu)

HN NH HN NH

S S 1,3-Imidazolidinene-2-thione (Imt) 1,3-Diazinane-2-thione (Diaz)

Scheme 1: Structures of the ligands used in the study.

mixing of thiones to AgNO resulted in colorless solutions, 2 Experimental section 3 while for Dmtu, Diaz, and Imt white precipitates formed on mixing. The mixtures were stirred for 15 min and then 2.1 Chemicals one equivalent KSCN solution was added. The addition of KSCN to Tu, Metu, and Tmtu solutions resulted in white AgNO was a product of Panreac Química S.A. 3 precipitates, while in the case of the 2:1 system of Dmtu, (­Castellar del Vallès, Spain). KSCN was obtained Diaz, or Imt:Ag(I), a colorless solution was obtained, from Merck (Darmstadt, Germany). N-Methylthiourea which upon evaporation of some solvent yielded white (Metu), N,N′-dimethylthiourea (Dmtu), and N,N,N′,N′- precipitates. The white precipitates of the 1:1 mixture of tetramethylthiourea (Tmtu) were obtained from Acros Dmtu and Ag(I) did not dissolve on addition of KSCN and Organics (Pittsburgh, PA, USA). Imidazolidine-2-thione therefore the product was collected from the filtrate (the (Imt) and 1,3-diazinane-2-thione (Diaz) were synthesized residue was discarded). The white precipitates in all cases according to the procedures described in the literature [16]. were filtered, washed with , and air dried. The product yield is about 40–50 %, except for the 1:1 system of Diaz:Ag(I), for which it is only 15 %. The elemental 2.2 Preparation of (thione)–AgSCN analysis and melting points of the complexes are given in complexes Table 1.

The complexes were prepared by adding 1 or 2 mmolar solutions of Dmtu, Tmtu, and Diaz (for Tu, Metu, and Imt 2.3 Spectroscopic data complexes only 2 mmolar) in methanol (Tu in water and –1 Imt in acetonitrile) to 0.17 g AgNO3 (1 mmol) in metha- IR (KBr pellet, cm ): AgSCN, ν = 2142; [(Tu)Ag(SCN)], ν = nol followed by the addition of an aqueous solution of 705, 2099, 3190, 3383 (Tu, ν = 732, 3156, 3365); [(Metu) 0.10 g KSCN (1 mmol). In the case of Tu, Metu, and Tmtu, Ag(SCN)], ν = 627, 2110, 3375, 3177 (Metu, ν = 634, 3163,

Table 1: Elemental analysis and melting points of the complexes.

Complexes Found (calcd.) in % m.p. (°C)

C H N S

[(Tu)Ag(SCN)] 9.6 (9.9) 1.4 (1.7) 15.6 (17.4) 24.9 (26.5) 154–156 [(Metu)Ag(SCN)] 14.5 (14.1) 2.4 (2.4) 15.8 (16.4) 25.6 (25.0) 119–121 [(Dmtu)Ag(SCN)] 18.4 (17.8) 3.2 (3.0) 15.0 (15. 6) 22.7 (23.7) 111–118

[(Tmtu)(AgSCN)1.5] 18.7 (20.5) 2.7 (3.1) 12.1 (12.9) 20.5 (21.0) 206–207 [(Diaz)Ag(SCN)] 21.9 (21.3) 3.1 (2.9) 14.0 (14.9) 21.8 (22.7) 119–121 M.N. Tahir et al.: Synthesis and characterization of silver(I) complexes of thioureas and thiocyanate 543

3245); [(Dmtu)Ag(SCN)], ν = 638, 2096, 3226 (Dmtu, Table 2: Crystal structure data for compound 1.

ν = 641, 3203); [(Tmtu)(AgSCN)1.5], 610, 2105 (Tmtu, ν = Formula C H AgN S 622); [(Diaz)Ag(SCN)], ν = 520, 2100, 3250 (Diaz, ν = 510, 5 8 3 2 M 282.13 3200). – 1H NMR (500 MHz, DMSO, 24 °C, TMS, ppm): r Crystal system Monoclinic [(Tu)Ag(SCN)], δ = 7.65, 8.10 (Tu, δ = 6.98, 7.25); [(Metu) Space group C2/c Ag(SCN)], δ = 2.78, 2.79, 7.88, 8.42, 8.61 (Metu, δ = 2.68, a, Å 20.542(2) 2.87, 6.95, 7.45, 7.65); [(Dmtu)Ag(SCN)], δ = 2.80, 3.04, 8.13, b, Å 13.7782(11) c, Å 6.7186(6) 8.43 (Dmtu, δ = 2.85, 7.38); [(Imt)2Ag(SCN)], δ = 3.70, 8.75 β (Imt, δ = 3.62, 7.98); [(Diaz)Ag(SCN)], δ = 1.78, 3.22, 8.66 , deg 106.569(5) V, Å3 1822.7(3) δ = 13 (Diaz, 1.75, 3.15, 7.81). – C NMR (125.65 MHz, DMSO, Z 8 TMS, ppm): [(Tu)Ag(SCN)], δ = 178.7, 124.5 (Tu, δ = 183.81); –3 ρcalcd., g cm 2.056 –1 [(Metu)Ag(SCN)], δ = 30.2, 31.5, 124.6, 175.4, 179.4 (Metu, μ(MoKα), mm 2.610 δ = 29.9, 31.1, 181.1, 184.1); [(Dmtu)Ag(SCN)], δ = 29.6, 32.1, F(000), e 1104 3 124.3, 176.1 (Dmtu, δ = 30.7, 182.7); [(Imt) Ag(SCN)], δ = Crystal size, mm 0.34 × 0.18 × 0.16 2 Temperature, K 296(2) 44.7, 126.8, 179.5 (Imt, δ = 44.0, 183.4); [(Diaz)Ag(SCN)], δ = Radiation: λ, Å MoKα; 0.71073 18.2, 40.0, 124.5, 169.38 (Diaz, δ = 19.2, 39.8, 175.6). 2θ range, deg 2.069–26.494 h,k,l limits –25:24/–17:17/–8:8

Refl. total/unique/Rint 1886/1886/– 2.4 IR and thermal measurements Reflections observed with I > 2σ(I) 1352 Data/ref. parameters 1886/101 R /wR (I < 2σ(I)) 0.0398/0.0981 The solid-state IR spectra of the ligands and their thiocy- 1 2 R1/wR2 (all data) 0.0630/0.1105 anato silver(I) complexes were recorded on a Perkin-Elmer Goodness of fit (F2) 1.093 FTIR 180 spectrophotometer using KBr pellets over the Largest diff. peak/hole, e Å–3 0.74/–0.65 range 4000–400 cm–1. Thermal analysis was carried out on a Mettler Tolledo TGA/SDTA 851e analyzer USA under argon atmosphere at a heating rate of 10 °C min–1. were positioned geometrically (C–H = 0.97 Å, N–H =

0.86 Å) and refined as riding with Uiso(H) = 1.2 × Uequ of the atoms to which they are attached. For molecular graphics 2.5 1H and 13C NMR measurements the program Platon [24] was used. CCDC 1030273 contains the supplementary crystallo- 1 The H NMR spectra of the complexes in [D6]DMSO were graphic data for this paper. These data can be obtained obtained on a Jeol JNM-LA 500 NMR spectrometer operat- free of charge from the Cambridge Crystallographic Data ing at a frequency of 500.00 MHz at 297 K using 0.10 m Centre via www.ccdc.cam.ac.uk/data_request/cif. solution. The 13C NMR spectra were obtained at a frequency of 125.65 MHz with 1H broadband decoupling at 298 K. The spectral conditions were 32 K data points, 0.967 s acquisi- 3 Results and discussion tion time, 1.00 s pulse delay, and 45° pulse angle. The 1H 13 and C chemical shifts were measured relative to TMS. The reaction of AgNO3 with thiones in a 1:1 or 1:2 molar ratio in the presence of KSCN in methanol–water media

resulted in products of composition [(thione)(AgSCN)n] 2.6 X-ray structure determination (n = 1 or 1.5). We attempted to prepare the following silver(I) complexes containing a thioamide and thiocyanate as

Single crystal data collection was performed at 296 K on a ligands: [(Tu)AgSCN], [(Metu)2AgSCN], [(Dmtu)AgSCN],

Bruker Kappa APEXII CCD diffractometer equipped with a [(Dmtu)2AgSCN], [(Tmtu)(AgSCN)], [Tmtu)2(AgSCN)], four-circle goniometer and using graphite monochroma- [(Diaz)(AgSCN)], and [(Diaz)2(AgSCN)]. The melting points tized MoKα radiation. Crystal data and details of the data and results obtained by elemental analysis and thermal collection are summarized in Table 2. The investigated methods or X-ray crystallography indicated that for Dmtu, crystal was found to be twinned. The twin matrix (1 0 1.743, Tmtu, and Diaz, same products were formed with both 1:1 0 1 ̅ 0, 0 0 1)̅ was found using the program Rotax by Parsons and 1:2 molar ratios of reagents. In the case of Tmtu, the and Gould [22] and subsequent refinement was done with product was 1:1 even though the amount of added ligand an HKLF 5 type of file with Shelxl-97 [23]. The H atoms was doubled in one case. 544 M.N. Tahir et al.: Synthesis and characterization of silver(I) complexes of thioureas and thiocyanate

3.1 IR and NMR studies observation for AgCN complexes [12]. The presence of a resonance at about 125 ppm in 13C NMR indicates the The selected IR frequencies of thioamides and their silver coordination of SCN– to silver(I). The CN resonance in the thiocyanate complexes are given in the Experimental corresponding AgCN complexes was observed around section. In the IR spectra of thiones, the characteristic 143 ppm [12, 13]. bands are expected in three frequency regions: ν(C = S) appears around 500 or 600 cm–1, ν(C–N) bands at about 1500 cm–1, and ν(N–H) near 3200 cm–1. A low-frequency 3.2 Thermal studies shift in the ν(C = S) band (except in 1) and a high-frequency shift in the ν(N–H) bands in the complexes compared to The isolated tetramethylthiourea complexes (expected to the free ligands indicate the existence of thione forms in be [(Tmtu)1Ag(SCN)] and [(Tmtu)2Ag(SCN)]) were insolu- the solid state. A sharp band around 2100 cm–1 for SCN– ble in DMSO; therefore, their NMR could not be recorded stretch was observed for all the complexes indicating its and they were characterized by thermal analysis. Thermal binding with silver(I). degradation of the complexes was monitored up to 740 °C. 1 13 The H and C chemical shifts of the complexes in [D6] The thermal behavior of the expected [(Tmtu)2Ag(SCN)] DMSO are summarized in the Experimental section. In is illustrated in Fig. 1. The decomposition starts at 206 °C the 1H NMR spectra of the complexes, the N–H signals of and is completed at about 740 °C. The endothermic tran- the thioamides were shifted upon coordination downfield sition at 206.4 °C is associated with the melting point of from their positions in free ligands. A slight downfield the complex. The decomposition of [(Tmtu)1Ag(SCN)] shift was also observed for other protons, which is related also started at 206 °C associated with an endothermic to an increase in π electron density in the C–N bond upon transition and followed a similar pattern as observed for coordination. The appearance of the N–H signal shows [(Tmtu)2Ag(SCN)]. The calculated weight losses for the that the ligands are coordinated to silver(I) via the thione release of one or two Tmtu ligands from [(Tmtu)1Ag(SCN)] group. The N–H protons of Metu are nonequivalent. The and [(Tmtu)2Ag(SCN)] are 44.3 % and 61.4 %, respectively.

N–H and CH3 (2.85 ppm) protons of Dmtu are equivalent, However, the thermogram (Fig. 1) shows that the weight but after coordination they become nonequivalent (δ loss due to removal of Tmtu ligands is about 35 % at

CH3 = 2.80, 3.04 ppm). A similar observation was made in 320 °C. This decomposition pattern suggests that the most 1 the H spectrum of [(Dmtu)AgCN] [12]. probable formula of the complexes is [(Tmtu)(AgSCN)1.5], In 13C NMR, the > C = S resonance of the ligands in the for which the percentage value is 34.7 % for the loss of complexes is shifted upfield by about 4–7 ppm as com- Tmtu. The remaining weight of ∼ 65 % beyond 320 °C cor- pared to the resonances of free ligands in accordance responds to AgSCN, which slowly releases thiocyanate. with the data observed for other complexes of copper(I) Previously, we reported that the analogous cyanido [25], silver(I) [12–15, 18, 26, 27], and gold(I) [16, 17, 28, 29] complex exhibits a polymeric structure with the composi- with thiones. A shift of this magnitude is diagnostic for tion [(Tmtu)(AgCN)2]n [11].

S-bonded thiones, ascribed to back-bonding from the Thermal degradation of intended [(Dmtu)2Ag(SCN)] metal d orbitals to the antibonding π orbitals of sulfur shows a weight loss of about 33 %, but the calculated in the > C = S bond, which will not only reduce the > C = S value for the loss of Dmtu is 52.0. This value is consist- bond order but also shield the carbon atom of > C = S ent with the formula [(Dmtu)Ag(SCN)] (calculated 35.2 %). group resulting in a high field shift [12–18]. As the shift The expected Dmtu complexes, [(Dmtu)1Ag(SCN)] and difference of the > C = S resonance may be related to the [(Dmtu)2Ag(SCN)], exhibit similar decomposition behav- strength of the metal-sulfur bond [12–15], the data show ior showing that the composition of the resulting com- that the Dmtu complex should be the most stable among pound is the same. The decomposition of the complex the examples. A small deshielding effect is observed in starts at 118 °C and is complete in one step at 478 °C. The other carbon atoms, which is due to an increase in π char- exothermic transition represents the melting point of the acter of the C–N bond. It should be noted that Metu gives complex as shown in Table 1. The weight loss of 40 % two signals for both > C = S and N–CH3 carbons showing at 478 °C corresponds­ to the removal of only one Dmtu that the compound exists in two isomeric forms in solu- ligand from the complex (calcd wt loss = 38.5 %). AgSCN tion form that could be due to a rotation barrier in the remains stable until 740 °C. Thus the proposed formula of

C–N bond. For [(Dmtu)AgSCN], two signals are observed both complexes is [(Dmtu)1Ag(SCN)], although in the pre­ for N–CH3 groups suggesting that the methyl groups paration, the molar ratio of Dmtu to AgSCN was different­ become nonequivalent upon coordination similar to our (1:1 and 2:1). M.N. Tahir et al.: Synthesis and characterization of silver(I) complexes of thioureas and thiocyanate 545

DDSC/(mW/mg/min) TG/% DSC/(mW/mg) Peak 206.4 °C, 0.009809 mW/mg ↓ exo 0 100 6

–2 90 4 –4 80 2 –6 70

–8 0

60

–10 –2 50 –12 –4 40 100 200 300 400 500 600 700 Temperature (°C)

Fig. 1: Thermogravimetric and DSC (as well as differential DSC) curves of [(Tmtu)(AgSCN)1.5]. The peak at 206.4 °C indicates the melting point of the complex.

3.3 Crystal structure description of 1 Table 3: Selected bond lengths (Å) and bond angles (deg) for 1.

The molecular structure of 1 together with the atomic Bond distance Bond angles labeling scheme is shown in Fig. 2. selected bond lengths Ag(1)–S(1) 2.6245(13) S(1)–Ag(1)–S(1) 120.16(5) and angles are presented in Table 3. The complex exists Ag(1)–S(1) 2.6284(14) S(1)–Ag(1)–S(2) 115.81(4) in the form of a polymer consisting of Ag(μ -Diaz)(μ -SCN) Ag(1)–S(2) 2.5813(13) S(1)–Ag(1)–S(2) 99.13(4) 2 2 Ag(1)–S(2) 2.5998(14) S(1)–Ag(1)–S(2) 99.50(4) units. The silver atom is coordinated to two μ -sulfur 2 C(2)–S(2) 1.724(5) S(1)–Ag(1)–S(2) 114.20(5) μ atoms of Diaz and to two 2 thiocyanate sulfur atoms in a C(2)–N(1) 1.322(6) S(2)–Ag(1)–S(2) 108.25(5) distorted tetrahedral geometry. The Ag(μ2-Diaz)(μ2-SCN) C(5)–N(1) 1.462(7) Ag(1)–S(2)–C(2) 110.24(16) C(1)–S(1) 1.653(6) Ag(1)–S(2)–C(2) 107.42(17) C(1)–N(3) 1.166(7) Ag(1)–S(1)–C(1) 98.33(18) Ag(1)···Ag(1) 3.3595(3) Ag(1)–S(1)–Ag(1) 79.52(4) Ag(1)–S(2)–Ag(1) 80.84(4) N(3)–C(1)–S(1) 178.3(5) N(1)–C(2)–S(2) 122.2(4) N(1)–C(2)–N(2) 120.1(4)

C1 N3 S1

Ag1 units are arranged in the form of a four-membered ring N2 C3 C2 and are repeated to form a double stranded polymeric chain (Fig. 2). The S–Ag–S(Diaz) angles are greater than S2 C4 the S–Ag–S(SCN) angles. The Ag–S and other distances N1 C5 are comparable to the values reported for other Ag(I)– thione complexes [7, 11, 18–21, 30]. The longer Ag–S dis- tance for SCN suggests its comparatively weaker binding compared to the Diaz ligand. The angles around the sulfur atom lie in the range expected for a tetrahedral Fig. 2: The polymeric chain of [(Diaz)Ag(SCN)] (1) drawn parallel to environment except for Ag–S–Ag, which is 80.79(5)° the crystallographic a axis. (Table 3). The SCN moiety is linear with a bond angle of 546 M.N. Tahir et al.: Synthesis and characterization of silver(I) complexes of thioureas and thiocyanate

Table 4: Hydrogen bonds in the crystal structure of 1 (Å, deg). [6] F. B. Stocker, M. A. Troester, D. Britton, Inorg. Chem. 1996, 35, 3145. Donor–H···Acceptor D–H H···A D···A ∠(D–H···A) [7] F. B. Stocker, D. Britton, V. G. Young, Inorg. Chem. 2000, 39, 3479. N1–H1···S1 0.86 2.62 3.445(4) 161.7 [8] E. R. Atkinson, D. J. Gardiener, A. R. W. Jackson, E. S. Raper, N2–H2···N3 0.86 2.19 3.038(7) 170.7 Inorg. Chim. Acta 1985, 98, 35. C3–H3B···S2 0.97 2.81 3.573(6) 136.3 [9] E. Dubler, W. Bensch, Inorg. Chim. Acta 1986, 125, 37. [10] M. Mufakkar, S. Ahmad, I. U. Khan, H. K. Fun, S. ­Chantrapromma, Acta Crystallogr. 2007, E63, m2384. [11] M. Hanif, S. Ahmad, M. Altaf, H. Stoeckli-Evans, Acta 178.6(8)°. Although the composition of the compound is ­Crystallogr. 2007, E63, m2594. similar as in [Ag(Tu)SCN], the two structures are signifi- [12] S. Ahmad, A. A. Isab, W. Ashraf, Inorg. Chem. Commun. 2002, cantly different [21]. 5, 816. [13] W. Ashraf, S. Ahmad, A. A. Isab, Transition Met. Chem. 2004, The silver atoms in the chain are connected to each 29, 400. other by weak argentophilic interactions. The Ag1···Ag2 [14] S. Ahmad, A. A. Isab, M. Arab, Polyhedron 2002, 21, 1267. distance is 3.3595(3) Å, which is somewhat shorter than [15] S. Ahmad, A. A. Isab, H. P. Perzanowski, Transition Met. Chem. the sum of the van der Waals radii of two silver atoms 2002, 27, 782. (3.44 Å) [31–33]. The corresponding distances in other [16] S. Ahmad, A. A. Isab, H. P. Perzanowski, Can. J. Chem. 2002, reported complexes are [Ag(Tmtu)(AgCN) ], 3.6965 Å [11], 80, 1279. 2 [17] A. A. Isab, M. B. Fettouhi, S. Ahmad, L. Ouahab, Polyhedron [Ag(Dmtu)2Ag(CN)2], 3.12 Å [7], and [Ag(Dmtu)2]ClO4, 3.21 Å 2003, 22, 1349. [34]. The argentophilic interactions in crystals of 1 result [18] S. Nawaz, A. A. Isab, K. Merz, V. Vasylyeva, N. Metzler-Nolte, in a stabilization of the chain structure. M. Saleem, S. Ahmad, Polyhedron 2011, 30, 1502. In the crystals, hydrogen-bonding interactions [19] M. B. Ferrari, G. F. Fava, M. E. V. Tani, Cryst. Struct. Commun. occur, involving each of the two N–H groups and the 1981, 10, 571. [20] G. A. Bowmaker, C. Pakawatchai, S. Saithong, B. W. Skelton, thiocyanate sulfur or nitrogen atoms. Details are given A. H. White, Dalton Trans. 2009, 2588. in Table 4. [21] M. R. Dupa, G. Henke, B. Krebs, Inorg. Chim. Acta 1976, 18, The present report shows that thioamides and thio- 173. [22] http://www.crystal.chem.ed.ac.uk/resource/ (accessed May cyanate react with AgNO3 to form complexes of the type 2015). [(thioamide)n(AgSCN)n] in which the ligands coordinate in the thione form in solution as well as in the solid state. [23] G. M. Sheldrick, Acta Crystallogr. 2008, A64, 112. [24] A. L. Spek, Acta Crystallogr. 2009, D65, 148. The crystal structure of one example shows that it exists [25] A. A. Isab, M. S. Hussain, Transition Met. Chem. 1986, 11, 298. in the form of a double stranded polymer, in which Diaz [26] A. A. Isab, Transition Met. Chem. 1992, 17, 374. binds to silver(I) through bridging sulfur atom exhibiting [27] J. S. Casas, E. G. Martinez, A. Sanchez, A. S. Gonzalez, a tetrahedral coordination. J. Sordo, U. Casellato, R. Graziani, Inorg. Chim. Acta 1996, 241, 117. [28] A. A. Isab, M. S. Hussain, Polyhedron 1985, 4, 1683. [29] A. A. Isab, M. S. Hussain, J. Coord. Chem. 1986, 15, 125. References [30] P. C. Zachariadis, S. K. Hadjikakou, N. Hadjiliadis, S. Skoulika, A. Michaelides, J. Balzarini, E. De Clercq, Eur. J. Inorg. Chem. [1] G. A. Bowmaker, B. W. Skelton, A. H. White, Inorg. Chem. 2009, 2004, 2004, 1420. 48, 3185. [31] P. Pyykko, Chem. Rev. 1997, 97, 597. [2] P. J. Cox, P. Aslanidis, P. Karagiannidis, S. Hadjikakou, Inorg. [32] H. Schmidbaur, A. Schier, Angew. Chem. Int. Ed. 2015, 54, Chim. Acta 2000, 310, 268. 746. [3] J. S. Cases, M. S. Garcia-Tasende, J. Sordo, Coord. Chem. Rev. [33] R. Lescouezec, L. M. Toma, J. Vaissermann, M. Verdaguer, F. S. 2000, 209, 197. Delgado, C. Ruiz-Perez, F. Lloret, M. Julve, Coord. Chem. Rev. [4] D. R. Smith, Coord. Chem. Rev. 1997, 164, 575. 2005, 249, 2691. [5] P. G. Eller, D. C. Bradley, M. B. Hursthouse, D. W. Meek, Coord. [34] C. Pakawatchai, K. Sivakumar, H. K. Fun, Acta. Crystallogr. Chem. Rev. 1977, 24, 1. 1996, C52, 1954.