Gold Chemistry with Ferrocene Derivatives as Ligands
M ConcepciOn Gimeno and Antonio Laguna Universidad de Zaragoza-CSIC Departamento de Qufmica lnorganica-ICMA E 50009, Zaragoza, Spain
Received: 26 February 1999 The synthesis and properties of gold complexes with l,l'-bis(diphenylphosphino)ferrocene (dppf), its sulfide (dppfS2) and disubstituted dithiocarbamate or thiolate ferrocene derivatives as ligands are reviewed. The ability of these metalloligands to modify their steric bite in order to adapt to different geometric requirements of the metal centres has allowed the synthesis of several gold complexes with unusual geometries and novel structures. The potential of the new compounds for a number of applications is considered.
Organometallic ligands provide a convenient route to the first derivatives of this type to be reported (5, 6). By synthesis of heterometallic complexes. Amongst these reaction of the corresponding organa lithium ligands ferrocene derivatives have been the most widely derivatives with [AuPPh3]+ precursors the mono- and studied. Due to the high stability of ferrocenes and the di-aurated complexes, [(CsHS) Fe(CsH4AuPPh3)] and well-established methods for their incorporation into [Fe(CsH4AuPPh3) 2]' could be obtained (7). These more complex structures, they have become versatile complexes can incorporate additional [AuPPh3]+ building blocks for the synthesis of compounds with fragments, to give [(CsHs)Fe(CsH4)(AuPPh3h]+ or tailor-made properties (1-4). Ferrocene-containing [Fe{(CsH4)(AuPPh3hh]2+ (6, 7) as is shown in complexes are currently receiving much attention Equation 1: associated with their widespread utility, eg in organic synthesis, production of fine chemicals, homogeneous ©r-AUPPh3 catalysis, and materials chemistry. Fe Numerous derivatives have been reported in which the Ph3PA~ cyclopentadienyl rings of ferrocene carry organic groups with one or more donor atoms. An important feature of these potential ligands is their flexibility: the bidentate The bonding situation in the latter complexes has representatives can adapt as chelating groups to different been described in terms of 3-centre-2-electron bonding, geometric requirements of a given metal centre and act as but resonance structures in which the aromaticity of the bridging ligands. Some of the complexes obtained with ring is lost and the positive charge delocalized over the these ligands have interesting redox properties and unusual ring are also acceptable. The short Au···Au distances structures (1-4). The coordination of ferrocene and of (2.77 A) and narrow Au-C-Au angles (78°) are indicative mono- or di- substituted diphenylphosphino, dipheny• of a strong interaction between the gold centres. lthiophosphoryl, dithiocarbamate and thiolate derivatives to gold(I) and gold(III) leads to interesting three- or four• coordinate mono- and polynuclear gold complexes. COMPLEXES WITH P-SUBSTITUTED FERROCENE LIGANDS FERROCENYL COMPLEXES The diphosphine 1,1 'bis (diphenylphosphino) ferrocene Ferrocenylgold compounds with the gold centre (dppf) has received a great deal of attention due to its directly attached to the cyclopentadienyl rings were the chemical uniqueness and industrial importance (1). It
90 C6\9' Gold Bulletin 1999, 32 (3) can act as a bridging or chelating ligand in two-, three-, they show no superior properties to those for and four-coordinated gold(1) and gold (III) compounds evaluated previously (10). compounds. Displacement of tetrahydrothiophene The reaction of dppf with [AuCI(SR2) lleads to the (tht) in gold(1) complexes such as [AuX(tht) 1 (X=CI, formation of the chloro complexes [(dppf)(AuClhl (1, C6FS), [Au(tht)LlCI04 (L=phosphine, ylide) or X=Cl) , [AuCI(dppf)l and [AuCI(dppfhL depending [Au(ththlCI04 by the diphosphine leads to neutral on the molar ratio used (8, 9, 12, 13). The 197Au and representatives [(dppf)(AuXhl (1) (Box 1), to cationic S7Fe Mbssbauer and 31 P NMR spectroscopic data of dinuclear complexes [(dppf)(AuLh](CI04h and to the products indicate the existence of two different three- and four-coordinate mononuclear derivatives gold (I) coordination geometries in the solid state: [(dppf)AuPR3lCl04 (2) and [Au(dppf)2lCl04 (8a) linear and trigonal (11). The dinuclear respectively. The crystal structure of [(dppf)(AuClhl has only marginal activity against the [(dppf)AuPPh3lCl04 indicates a trigonal-planar Au P388 leukaemia mouse model (12) . The crystal coordination. The Au-P distances (2.343 - 2.409 A) structure of one of its known modifications shows a are shorter than the Ag-P ones (2.424 - 2.480 A) in the nearly linear P-Au-CI unit and intermolecular gold• analogous [(dppf)AgPPh3lCI04 (8b), in agreement gold contacts of 3.083(1) A (12), whereas no Au .. ·Au with theoretical predictions (8c). [Au(dppf) 2l CI04 interactions have been found in other modifications of undergoes a dimerization process with liberation of the same compound (14) . The reaction of one dppf and formation of [(dppf)Au(r• [(dppf)(AuCI) 2l with dppf (1: 1 molar ratio) gives dppf) AU(dppf) ](CI04) 2 (3) which contains bridging [AuCI(dppf) 1 as an intermediate, which readily and chelating diphosphines (8b). The same dication is polymerizes to give a chain polymer based on trigonal present in [(dppf)Au(r-dppf)Au(dppf)](N03)2, CIAuP2 units (4) (9, 13). obtained by the reaction of dinuclear [(dppf)(AuCI) 2l From [(dppf)(AuCl) 2l other dinuclear complexes with AgN03 and NaHC03 (9). Cyclic voltammetry of [(dppf)(AuXhl (X Br, 1, 2-pyridinethiolate some of these compounds reveals one chemically (Spy) or S2CNR2) can be obtained (14). reversible phosphinoferrocene-based oxidation (9). The complex [(dppf)(AuSpYhl with its nitrogen donor atom can coordinate to [AuPPh2Mel+ units to give the polynuclear compounds Box 1 [(dppf){AuSpy(AuPPh2Me)hl (OTfh (OTf = CF3S03) ~Ph2 -Q.r-P-AuX and [(dppf){AuSpy(AuPPh2Mehh](OTf)4. The latter decomposes in solution and the trinuclear complex Ph 2 Fe XAU-~ [AU3(r-dppf)(r3_Spy)(PPh2Me)](OTf)2 (5) (Box 2) is obtained, which represents the first example where a (1) pyridinethiolate ligand bridges three gold centres. The gold atoms have geometries slightly distorted from <@rP-AUPhl P].. .. linearity, probably due to the weak gold-gold CI" Ph2 Fe . '. PPh Alr ..[ .. ~ 2 interactions (3.0985(12) and 3.2105(13) (A) (14). Ph (' n 2 The reaction of [(dppf)(AuClhl with an excess of (4) LiR in diethyl ether affords the organa gold (I) -dppf complexes [(dppf)(AuR) 2l [R = Me, Ph, I-naphthyl, 9- anthryl, pyren-l-yl(CI6H g), C==CPh, C==CButl. Similar complexes, such as the dinuclear Their photophysical and electrochemical properties [(dppomf)(AuXhl (X = CI, C6FS) or the mononuclear have been studied (15). Excitation of these complexes at three-coordinate compounds [(dppomf)AuXl can be X. > 330 nm gives weak emissions in dichloromethane obtained using the related diphosphine 1, 1'• solutions. The electrochemical data show a quasi• bis(diphenylphosphino)octamethylferrocene (dppomf) reversible wave, due to the oxidation of the dppf, and (10) . The gold atom is trigonal planar in an irreversible one assigned to Au (I) - Au (II) [(dppomf)AuCll. Electrochemical studies (10) show oxidation. The structure of [(dppf){Au(CI6Hg)hl is the formation of Fe (III) derivatives of the similar to that of the chIaro derivative. The metallophosphine gold(1) complexes, which can also be heterometallic complexes [(dppf)(Au{M(CO) s}hl obtained by direct reaction of the precursors with (M = Mn, Re (6)) are obtained by the reaction of electrochemically generated [FeCp2l+. The cytotoxic [(dppf)(AuClhl with Na[M(CO)Sl (16). However, properties of these complexes have been studied, but reaction with K2[Pd(CN)4l results in ligand
~ GoldBulletin 1999,32(3) 91 displacement with formation of [(dppf){Au(CN)12] Box 3 instead of metal-metal bond formation. The X-ray p.p = dppf; E = S or S e z photoelectron spectroscopic data for complex 6 suggest MePh "" l 2+ a polarization of the AuB+- ReB- bonds (16). The :~ complexes [M(CO)S(dppf)] (M = Cr, Mo, W) behave A~:;\ MePhzl""" AU""Au like a mono dentate phosphine ligand and react with rf \p [AuCl(SMe2)] to yield the heterometallic complex (8) '------"' [M(CO)S(r-dppf)AuCl] (17).
Box 2
2+ <.9r~~UrFe : o ~
coordination sphere of the sulfur atom in 8 can be RCHO + CNCH2COOEr - nN + HN regarded as a trigonal bipyramid with one of the apical 0-...,; 0-...,; (2) positions occupied by the lone pair of electrons and the other by the gold atoms. The complex is electron• Diferrocenylphenylphosphine (PF C2Ph) [F c = deficient, however, since only three bonding molecular (CsHs)Fe(CsH4)] reacts with gold(1) derivatives to orbitals are occupied (19, 20). All these complexes afford the neutral or cationic complexes, display short gold-gold interactions. The reactions of [AuX(PFc2Ph)] (X=Cl, C6FS) and [Au(PFc2Ph) [S (AU2dPPf)] with the gold (III) precursors (PR3)]Cl04 (PR3 = PFC2Ph, PPh3) (25). Ethynyl• [Au(C6F Sh(OEt2)] or [Au(C6F S) 2(OEt2) 2] OTf afford gold (I) complexes, such as [(PhF C2P) mixed-valence complexes [S(Au2dppf){Au(C6Fsh12]' AuC==CAu(PFc2Ph)] and [(PhC==CAu(PFc2Ph)], are [S(AU2dppf){Au(C6FSh}] (10), and [{S(AU2dppf)h{Au obtained by the reaction of [AuCl(PFc2Ph)] with (C6F S) 2}] OTf respectively (21, 22). The last two alkaline solutions of the corresponding ethyne (26). compounds show short gold (I) -gold (III) contacts None of these compounds have short intermolecular (3.2195 (8) -3.404(1) A) which have been studied by metal-metal contacts in solid state structure (25-27). theoretical calculations (22). Reaction of PFC2Ph with [AU(C6Fsh(OEt2)] and Analogous complexes have been prepared with E = [Au(C6FShClh gives the gold (III) complexes selenium. The reaction of [(dppf)(AuClh] with [AU(C6Fsh(PFc2Ph)] (12) and [Au(C6FShCl SeC(NH2b followed by basic hydrolysis, leads to (PF C2Ph)], respectively (25). [Se(Au2dppf)] (7) (Box 3), which further reacts with Other neutral or cationic gold(1) complexes, such as [AU(C6Fsh(OEt2)] to give [Se(Au2dppf) {Au (C6FSh}] [AuX{P (CH2Fc) Ph2}] (X Cl, C6FS) , (10) . The product shows weak gold (I) -gold (III) [Au{P(CH2Fc)PhVL]OTf [L = P(CH2Fc)Ph2, PPh3], interaction as indicated by a short Au (I) .... Au (III) [Au{P(CH2Fc)PhV3]OTf (13) and [AuX{P(CH2Fc)Ph212] distance of 3.541 (1) A (23). have been obtained, starting from the monophosphine Gold (III) complexes of the types P(CH2Fc)Ph2 (28). No intermolecular gold-gold [(dppf){Au(C6F S) 3}], [(dppf){Au(C6F S) 312] and contacts have been found in the crystal structures of
92 ~ GoldBuUetin 1999,32(3) Box 4 Box 5
Ph1PAU--s--© ©rS-AuPPhl "" Fe ©>-S-~ (15)
f6 F5 Ph2 Fe C6F' jU--C(h -C~ H, I H2 ~~ ©rC-=-P-Au Fe Fe Ph2 "- H~ Fe P-C~ <©> <©> <©> P~ Fe (12) (13) <9> these compounds. The reaction of P(CH2Fc)Ph2 with cyclopentadienyl rings, suggesting carbon-to-gold electron [AU(C6Fsh(OEt2)] leads to [Au(C6FSh{P donation, in agreement with theoretical calculations (33). (CH2F c) Ph2}] (28). With the hydroxymethyl• A similar situation may exist in the polymeric complex phosphine P(CH2Fc) (CH20Hh the linear two• [Fe(CsH4S2CNEt2) 2Ag]n(CI04)n (34). coordinate complex [Au{P(CH2F c)(CH20Hh12] CI The condensation reaction of has been described (29). ferrocenecarbaldehyde with [3-mercaptoethylamine gives FcCHN(CH2)2SH, which reacts with [AuCI(PPh3)] in the presence of Na2C03 to afford the thiolate complex [F cCHN (CH2) 2S (AuPPh3)]' COMPLEXES WITH S-SUBSTITUTED Further reaction of the latter in various molar FERROCENE LIGANDS ratios with [Au(OTf)PPh3] leads to [FcCHN(CH2h S (AuPPh3) 2] OTf, [F cCHN (AuPPh3) (CH2) 2S The oxidation of dppf with sulfur to give 1,1'• (AuPPh3h](OTfh (17) and [FcCHN(AuPPh3) bis(diphenylthiophosphoryl)ferrocene (dptpf), a ligand (CH2)2S(AuPPh3h](OTfh in which the gold centres with a longer and more flexible skeleton. The reaction are coordinated to the sulfur and nitrogen atoms (35). of dptpf with [Au (thth] OTf in a 1: 1 molar ratio leads Complex 17 shows short Au .. ·Au interactions for all to the complex [Au(dptpf)]OTf (14) (Box 5) with the three metal centres. The cyclic voltammograms (35) dptpf acting as a trans-chelating ligand (30). The show a quasi-reversible redox couple assigned to crystal structure reveals a linear coordination geometry ferrocene/ferrocenium species at potential values at the metal centre for this complex and its silver similar to those found in ferrocene itself. A small analogue. Three- and four-coordinate complexes have irreversible wave appears at higher potential (ca 0.8 V), been obtained with this ligand for silver, but not for probably due to an amine oxidation process. This gold (31). signal is absent for complexes with an [AuPPh3]+ unit The reaction of 1.1 '-dithiolferrocene, on the nitrogen atom. [Fe(CsH4SH)2], with [0(AuPPh3)3]BF4 gives the dinuclear complex [Ph3PAu(SCsH4) Fe(CsH4S- SCSH4)Fe(CsH4S)AuPPh3] (15), as the product of an oxidative coupling of the ligand (32). COMPLEXES WITH C-FUNCTIONAL 1,1' -Bis(diethyldithiocarbamato) ferrocene, FERROCENE LIGANDS [Fe(CsH4S2CNEt2h]' is another S-donor derivative with interesting ligand properties. It reacts with appropriate Phosphonium salts of the types [FcCH2PR3] Cl04 gold(I) or gold(III) precursors to give dinuclear complexes (PR3 = PPh3, PPh2Me) and [FcCH2PPh2CH2PPh2]X such as [Fe(CsH4S2CNEt2h(AuClh] (16), [Fe(CsH4S2 (X=Cl04, OTf), obtained by reaction of CNEt2) 2(AuPPh3) 2] (OTf) 2, [Fe(CsH4S2CNEt2) 2{Au [F cCH2NMe3] I with tertiary or ditertiary phosphines, (C6F S) 312], and [Fe(CsH4S2CNEt2) 2{Au(C6F S) 2Cl12] can act as precursors for C-donor ligands in gold (33). The crystal structure analysis of 16 reveals a new chemistry. Thus, the treatment of [FcCH2PR3]Cl04 type of Tj2-interaction between the gold centres and the with [Au (acac)(PPh3) ] leads to the ylide complexes
~ GoldBulletin 1999,32(3) 93 [FcCH(AuPPh3)PR3)]CI04, derived from substitution reported here and the Direccion General de Ensefianza of one proton of the methylene group by the Superior (Spain) for financial support. [AU(PPh3)]+ unit (Equation 3): ABOUT THE AUTHORS
Dr M Concepcion Gimeno is 'Cientifico Titular' at the Instituto de Ciencia de Materiales de Aragon, University of Zaragoza-CSIC. She completed her PhD The oxonium salt [O(AuPPh3)3]Cl04 can also act degree with Professors R Uson and A Laguna at the as deprotonating agent and reacts with University of Zaragoza (1988). In 1989 she was a [FcCH2PPh2CH2PPh2] Cl04 to give the trinuclear postdoctoral fellow at the University of Bristol under methanide complex [FcCH2PPh2C(AuPPh3)2 the supervision of Professor F G A Stone. She is the PPh2(AuPPh3)](CI04)2 (Equation 4) (36): author of more than 100 scientific papers on the organometallic and coordination chemistry of silver and gold. Professor Antonio Laguna completed his PhD degree with Professor R Us on in 1973. He completed a postdoctoral period at the University of Bristol in 1975 under the supervision of Professor F G A Stone. Since 1976 he has been at the University of Zaragoza as 'Professor Titular' or Professor of Inorganic Chemistry. CONCLUSIONS He is the author of over 200 scientific papers on the organometallic and coordination chemistry of silver Ferrocene is a versatile building block for the synthesis of and gold. ligands and complexes having interesting chemical and physical properties. One of the more important features is the flexibility of the bidentate ligands which permits REFERENCES the formation of gold(I) and gold(III) complexes with a number of different structural frameworks. These 'Ferrocenes: Homogeneous Catalysis, Organic Synthesis and Materials Science', ed. A. ferrocene derivatives can act as (a) bridging ligands in di• Togni and T Hayashi, VCH, Weinheim, 1995 or polynuclear derivatives, (b) as chelating agents in NJ Long, Angew Chem.In!. Ed Engl, 1995,34,21 gold(III) or three-coordinate gold(I) compounds, and (c) 3 'Metallocenes: Synthesis, Reactivity, Applications', ed. A. Togni and R.L. Halterman, through a new type of Tj2-interaction between the gold Wiley-VCH, Weinheim, 1998 centre and the cyclopentadienyl ring. NJ Long, 'Metallocenes: An Introduction to Sandwich Complexes', Blackwell Science, The coordination chemistry of gold is currently Oxford, 1998 attracting growing interest, arising both from the AN. Nesmeyanov, E.G. Perevalova, K.I. Grandberg, DA Lemenovskii, TV Baukova novel structures of the gold complexes and their and O.B.Afanasova. Vestn. MIBk. Uni~ Khim., 1973, 14,387 potential applications. Their potential use as AN. Nesmeyanov, E.G. Perevalova, K.I. Grandberg, DA Lemenovskii, TV Baukova anti-tumour agents is being investigated. and O.B. AfanasovaJ Organomet, Chem, 1974,65,131 Ferrocene/ferrocenium couples could find use in E.G. Perevalova, TV Baukova, MM. Sazonenko and K.I. Grandberg, BuB Acad Sd. biosensors and chiral ferrocene derivatives have USSR, Chem. Ser., 1985, 1726 potential in catalysis. Other application areas could 8a M.e. Gimeno, A. Laguna, e. Sarroca and PG. Jones, lnorg. Chem., 1993,32,5926 include use in the synthesis of materials for second• 8b M.e. Gimeno, PG. Jones, A. Laguna and e. Sarroca, j Chem. Soc., Dalton Tram., and third-order non-linear optical effects, magnetic 1995,1473 materials and ferrocene-based polymers. & WS. Rapson, Cold BuB, 1996, 29, 143 9 L.T. !'hang, TSA Hor, Z.Y. Zhou and TCW. Mak, j Organomet. Chem., 1994,469, 253 ACKNOWLEDGEMENTS 10 M. Violle, B. Gautheron, MM. Kubicki, Y. Mugnier and RV Parish, Inorg. Chem., 1995,34,3465 We wish to thank Professor Peter G Jones for solving 11 A. Houlton, R.M.G. Roberts, J. Silver and RV Parish, j Organomet. Chem., 1991, the crystal structures of many of the complexes 418,269
94 ~ GoldBuUetin 1999,32(3) 12 D.T. Hill, G.R. Girard, FL. McCabe, RK. Johnson, PD. Stupik, J.H. Zhang, WM. 25 M.e. Girneno, PG. Jones, A. Laguna and e. Sarroca, j Organomet, Chem., 1999, Reiff and D.S. Eggleston, /norg. Chem., 1989, 28,3529 579,206 13 A. Houlton, DM.P Mingos, D.M. Murphy, DJ WilliarT1'!, L.T. Phang and TSA 26 I.E. MOller, SWK. Choi, D.M.P Mingos, D. Murphy, DJ WilliarT1'! and VWW Hor,] Chem, SJe., Dalton Tram., 1993,3629 Yam,] Organomet. Chem., 1994,484,209 14 F Canales, M.e. Girneno, PG Jones, A. Laguna and e. Sarroca, /norg. Chem., 1997, 27 PG. Jones, e.F ErdbrOgger, R Hohbein and E. Schwarzmann, Acta Cryst., 1998, C44, 36,5206 1302 15 VWW Yam, SWK. Choi and K.K. Cheung,] Chem. Soc., Dalton Tram., 1996,3411 28 EM. Barranco, O. Crespo, M.e. Girneno, PG. Jones and A. Laguna, to be published 16 PN.N. Low. YK. Yan, H.S.O. Chan and TSA Hor, j Organomet, Chem., 1993,454, 29 NJ Goodwin and W Henderson, Polyhedron, 1998, 17,4077 205 30 M.e. Girneno, PG. Jones, A. Laguna and e. Sarroca, j Chem, Soc., Dalton Tram., 17 L.T. Phang, S.e.F Au-Yeung, TSA Hor, S.B. Khoo, Z.Y. Zhou and TCW Mak, j 1995,3563 Chem. Soc., Dalton Tram., 1993, 161 31 M.e. Girneno, PG. Jones, A. Laguna and e. Sarroca, j Chem, Soc., Dalton Tram., 18 F Canales, M.e. Girneno, A. Laguna and PG. Jones, j Am. Chem. SJe., 1996, 118, 1998,1277 4839 32 E.G. Perevalova, TV Baukova, MM. Sazonenko and K.I. Grandberg, Jz." Akad Nauk. 19 E. Zeller, H. Beruda, A. Kolb, P Bissinger, J. Riede and H. Schmidbaur, NatuIr!, 1991, SSSR, Ser: Khim, 1985, 1873 Bull, Acari, Sd, USSR, Di~ Chem. Sci, 1985, 34, 1722; 352,141 Chem., Ahrtr, 1985, 105, 97597x 20 F Canales, M.e. Girneno, A. Laguna and PG. Jones, Angew Chem. Int. Ed Engl., 33 M.e. Girneno, PG. Jones, A. Laguna, e. Sarroca, MJ Calhorda and L.F Veiros, 1994,33, 769 Chem. Ew: j, 1998, 4, 2308 21 F Canales, M.e. Girneno, A. Laguna and PG. Jones, OrganometaJlics, 1996, 15,3412 34 O. Crespo. M.e. Girneno, PG. Jones, A. Laguna and e. Sarroca, Chem. Commun. 22 MJ Calhorda, F Canales, M.e. Girneno, J. Jirn~nez, PG. Jones, A. Laguna and L.F 1998,1481 Veiros, OrganometaJlics, 1997, 16,3837 35 EM. Barranco, M.e. Girneno, PG. Jones, A. Laguna and M.D. Villacampa, /norg. 23 S. Canales, O. Crespo, M.e. Girneno, A. Laguna and PG. Jones, to be published Chem, 1999, 38, 702 24 A. Togni, S.D. Pastor and G. Rihs,] Organomet. Chem. 1990,381, C21 36 EM. Barranco, M.e. Girneno and A. Laguna, Inorg. Chim. Acta, 1999, 291, 60
Continued from page 89 GM. Vest and RW Vest, IntematlonaljoumaJ for Hybrid Microelectronics, 1982, 5, 62 REFERENCES Re. Hendricks and G. McDonald, NASA TechrucaJ Repom, NASA-TM-86992, 1985 M. Parkhurst, Engelhard-CLAL (UK) Ltd, personal communication, 1999 TV Jones, 4th National UK Heat Transfer Conference, Manchester, I Mech. E Con! I\pplication Data for Kodak Photosensitive Resists', Eastman Kodak Co., 1967 Tranr, C510/150, 1995, pJ 8 WK. Chu, JW Mayer and MA Nicolet, 'Backscattering Spectrophotometry', GJ Berry,lA Calms and J. Thomson, Senrorsand ActuatorsA, 1995, 51, 47 Academic Press, 1978 3 e.S.Pai, B. Zhang, DM. Scott and S.S. Lau, 'Materials Research Society Symposium 9 KL Chopra and I. Kaur, 'Thin Film Device Applications', Plenum Press, 1983 Proceedings, Thin Films and Interfaces II', ed. J.E.E. Baglin, D.R. Campbell and WK. 10 TD. McGee, 'Principles and Methods of Temperature Measurement', John Wiley and Chu, North Holland, 1983, 25, 639 Sons Inc, 1988 DO YOU WANT TO ADVERTISE IN THIS JOURNAL.
We are considering the introduction of a Interested advertisers should contact the limited amount of advertising in Gold Bulletin. Editor, Dr C.w. Corti, World Gold Council, If you are interested in reaching an Kings House, 10 Haymarket, international audience of scientists and London SW1Y 4BP, England. technologists in academia and industry with an Tel:+44 20 79305171 - Fax: +44 20 7839 6561 interest in gold, this could be your opportunity. E-mail: [email protected]
~ GoldBulletin 1999,32(3) 95