3 Al Ga In and TI By J. P. MAHER School of Chemistry University of Bristol Bristol BS8 7 TS UK The references for this chapter have been obtained largely by means of a computer- based search of the literature this gave 3600 references (!) with 70% referencing aluminium 15% gallium 10% indium and 5% thallium. A large proportion of aluminium work concerns metals alloys and their properties or the catalytic properties of various materials involving alumina where the alumina usually acts as a support material. The interest in gallium and to a lesser extent indium comes with the many semiconductor materials and devices. The rather low number of thallium references is perhaps surprising in view of interest in ‘low temperature’ superconduct- ing materials. Necessarily then this review is only a small selection of the work which caught the authors’ attention during the search and subsequent perusal of the journals.The chapter is subdivided according to compounds and interest areas rather than the particular Group 13 element. 1 Organometallic Highlights The organometallic chemistry of Group 13 is well reviewed each year,’ so I will only mention some of the more interesting new compounds which have been prepared during 1992. The first optically active organoaluminum alkoxides R,AlOR’ (R = Me Et Bu’; OR’ = 1-mentholate and 1-borneolate) have been prepared. The aza-18-crown-6 derivative Me,AI(N ,C,)AlMe, has both hexa- and tetra- coordinate al~miniums.~ One A1 atom is bonded to two Me groups the N atom and the two crown ether oxygen atoms nearest to the N atom the other A1 atom is bonded to three Me groups and the N atom.The first neopentyl-aminoalanes [Neo,Al- N (H )Ada] , [Neo,AI -N(H)Ph’1, [Neo ,A1-N-(H )P h (Pr ),], and [Neo,A1-N (H )-Bu‘], (Neo = CH,CMe, Ph’ = various phenyl derivatives Ada = l-adaman-tanamine (H,N-Ada)) have been ~repared;~ these are novel as sterically demanding alanes. The reactions of R,SiNH with R;AI has produced’ a new family of dimeric K. C. Mohy in ‘Organometallic Chemistry A Specialist Periodical Report’ The Royal Society of Chemistry 1991 20 56. M. L. Sierra. R.Kumar V. S.J. Demel arid J. P. Oliver Orgunornetallic,s 1992 11. 206. A. D. Pajerski T. P. Cleary M. Parvez,G. W. Gokel and H. G. Richey Jr. Orgunorneta/lic.s 1992.I1,1400.D. M. Choquette M. J.Timm. J. L. Hobbs M. M. Rahim K. J. Ahmed,and R. P. Planalp Oryunornerallics. 1992 11 529. R. L. Wells A. T. McPhail. and T. M. Speer Organornrtallics 1992. 11. 960. 23 24 J. P. Maher aluminum silylamides [R;AlN(H)SiR,] (R' = Me R = Ph, Et,; R' = Bu' R = Ph, R = Bu:H). The dimer [Et,AlAs-(SiMe,),], has been found6 to contain a planar A1-As-A1-As ring. The synthesis of various 5-membered ring organoalanes (aluminacyclopentanes) has been developed' using olefines or acetylenes and AlEt, assisted by catalytic amounts of Cp,ZrCl,. The first triorganoaluminum bis(phosphine) adduct with C3P2 pentacoordination at aluminum Al[o-(Ph,PCH,)C,H,], has been prepared.8 Two of the anionic phosphines act as chelating ligands spanning equatorial-(C atom) and axial-sites (P atom) the third phosphine is only carbon-bonded.The polymeric compound [(H,AI),(P(C,H 1)2CH2)2] also has trigonal bipyramidal aluminum centres with exceptionally long apical AI-P bonds.' The solid state structure of tris(trimethylsilyl)methylgallium,[Ga,(C(SiMe,),),] shows a tetrahedral Ga skeleton; the compound is stable in air for months and shows remarkable thermal stability." Reactions of BuiGa with elemental S Se or Te have been shown to give mixtures of interesting compounds among which are the cubanes [(Bu')GaS], [(Bu')GaSe], [(Bu')GaTe], and an octamer [(Bu')GaS],. '' The for- mation and structures of cage compounds which contain a central In,E cube [(Cp- (co2Fe)4In4Se,l [(CP(CO),M~)L~I%S~] [(CP (CO),Fe)4In4S4] 3 and [(CP(co)3-Mo),In,Te,] have also been described.' An organoindium compound with an In-Se bond [(Me,CCH,),InSePh], has been synthesized and characterized.' Most organoindium compounds are not air-stable however by incorporating a nitrogen base into the organic ligand air-stable pentacoordinate bis[3-(dimethylamino)propyl]indiumsare formed.l4 These are stabilized by intra-molecular nitrogen base coordination to the organoindium giving hexacoordinate indium atoms in a quasi-polymeric structure with one long In-N bond. 2 Nitrogen Ligands Group 13/Group 15 Lewis acid/base adducts are of great potential interest as precursors in the formation of epitaxial layers of 111-V materials by means of metal-organic chemical vapour deposition (MOCVD); this subject has been re-viewed.' AlCl,.xNH compounds are possible starting materials for the synthesis of AlN thus the reactions of melts of monoammine-aluminium chloride with ammonia have been investigated.16 They were found to react at 150°C to give [AlCl,(NH3),] [AICI,] for which an X-ray structure determination was carried out.AlCl reacts with Mg(NR,) to form Al,X,Mg[NEt,] (X = C1 Br) Al,X,(NR,) U. M. Dzhemiliv A. G. Ibragimov and A. B. Morozov J. Chem. Soc. Mendeleec Commun. 1992 1 26 U. M. Dzhemilev A.G. Ibragimov and A. P. Zolotarev J. Chem. Soc. Mendeleet. Commun. 1992,4 135. ' S. J. Schauer W. T. Pennington and G. H. Robinson Organometallics 1992 11 3287. G. Muller J. Lachmann and A. Rufinska Organomrtullics 1992 11. 2970. F.R.Bennett F.M. Elms M.G. Gardiner G.A. Koutsantonis C.L. Raston and N.K. Roberts Organometallics 1992 11 1457. 10 W. Uhl W. Hiller M. Layh and W. Schwarz. Angrw. Chern. Int. Ed. Enyl. 1992 31 1364. M. B. Power J. W. Ziller A. N. Tyler and A. R. Barron Organometullics 1992 11 1055. l2 K. Merzweiler F. Rudolph and L. Brands Z. Naturforsch. Teii B. 1992 47 470. 13 O.T. Beachley J. C. Lee. H. J. Gysling S. H. L. Chao M. R. Churchill. and C. H. Lake. Organometallics 1992 11 3144. l4 H. Schumann F. H. Gorlitz T. D. Seuss and W. Wassermann Chem. Ber. 1992 125 3. l5 D.K. Russell. Coord. Chem. Rev.. 1992 112. 131; F. Maury Adc. Muter.. 1991. 3. 542. l6 H. Jacobs and B. Nocker Z. Anorg. Ailg. Chem. 1992 614 25. All Ga in and T1 25 (R = Et Pri X = C1 Br) AlX,HNR (R = Pri); these were characterized by mass- infrared- and H-1 C-13 and A1-27 NMR spectroscopy and by elemental analyses." The crystal structures of AI,Cl,[NEt,] and AICl,HNPr' were determined.Infrared and Raman spectra of NaAl(NH,) and of deuterated samples have been measured.'* The high charge density of the AI3 ions causes the NH-stretching modes + to be shifted higher by as much as 200cm-' compared to those of free amide ions. Furthermore the H-bond donor strength of the NH ions are so enlarged that weak unusually long NH * * NH hydrogen bonds are formed. These H-bonds share layers of vertex-connected AI(NH,) and Na(NH,) tetrahedra within the structure. Evidence has been found during the electrochemical oxidation of indium metal in liquid ammonia solutions of NH,X (X = C1 Br or I) for formation of In" species at the anode." In the NH,I solutions Raman spectroscopy confirmed the presence of In214 but it was not possible to isolate neutral or anionic derivatives of In" since disproportionation occurs on removal of solvent to give In' In' and In"' derivatives.Solutions of NH,I with o-quinones gave InI3.3NH, while with substituted catechols the products were [NH,],[In(O2C6X4),]*Et20 [X = C1 or Br]. Another ortho-cathecol Bu:H,C,(OH) ( = (H,dbc)) gave the dimeric anion [1n,(db~),(NH,),]~- which involves two In0,N kernels with In,O cross-linking responsible for the dimerization. The treatment of p-tert-butylcalix[4]arene with [H,Al(NMe,)] results2' in trimetallation and deprotonation by the tertiary amine yielding the bis(calix[4]arene) [{ (1-H,)Al},][HNMe,], with included CH,Cl,.This unique calixC4)arene has a structure in which the distorted five-coordinate 0-bound aluminium centres fuse the slightly flattened cone calixarene units the methylene chloride H-atoms residing over two opposite aromatic rings in each cone involve a C-H . . n-arene interaction. There is continuing interest in niacrocyclic complexes of Ga"' and In"' thus the reaction of Li,(tmtaa) (tmtaa = dibenzotetramethyl-tetraaza[l4]annulene) with GaCl and InCl has been shown to give the complexes Ga(tmtaa)Cl and In(tmtaa)Cl re~pectively.~' The structure of the gallium complex was determined by X-ray analysis. The Ga-C1 bond is very unreactive but the In-Cl bond undergoes a slow reaction with MeLi to form In(tmtaa)Me.,l Various In"' and Tl"' porphyrin compounds have been investigated.Two new series of metal-metal bonded indium porphyrin complexes (tbpp)In-ML and (5fp)In-ML have been synthesized, (together with (oep)In-ML and tppln-ML) where tbpp is the dianion of 5,10,15,20-tetrakis(3,5-di-t-butylphenyl)porphyrin, 5fp is the dianion of 5,10,15,20-tetrakis(2,3,4,5,6-penta~uorophenyl)porphyrin, and ML is Mn(CO), Mo(CO),Cp and Co(CO),. The synthesis and characterization of In"' porphyrin complexes with three types of a-bonded tetraazolato axial ligands has been reported,, In(por)(N,CR) where R = CMe, CH=CH, or CH=CHCN and por = oep2-,tpp or 5,10,15,20-tetra-p-trifluoromethjlphenylporphyrin. The N,CR ligand of a given M(por).(N,CR) complex can have the R group attached to either the 4-or 5-position of l7 C.C.Chang S.C. Lin C. N. Tsai. and L. K. Liu J. Chin. Chem. SOL..(Toipri),1992 39 55. 18 H. D. Lutz N. Lange H. Jacobs and B. Yocker Z. Anorg. Allg. Chem. 1992. 613 83. '' T. A. Annan. J. S. Gu. Z. G. Tian and D. G. Tuck J. Chem. Soc.. Dalton Trans. 1992 3061. 2o J.L. Atwood S.G. Bott C. Jones and C. L. Raston J. Chrm. Soc,.,Chem. Commun. 1992 1349. *' D.A. Atwood V.O. Atwood A. H. Cowlry J. L. Atwood. and E. Roman. Inorg. Chem. 1992 31 3871. 22 S. Takagi Y. Kato H. Furuta S. Onaka and T. K. Miyarnoto J. Orgunomet. Chem. 1992 429. 287. 23 R. Guilard N. Jagerovic. A. Tabard.C. Naillon,and K. M. Kadish.J. Chem. Soc. Dalton Trans. 1992,1957. 26 J. P.Maher the tetraazolato ring. In the oxoporphyrin 5,15-dioxo-2,3,7,8,12,13,17,18-octaethyl-porphodimethene-thallium(rI1)chloride the structure consists of a penta-coordinated thallium ligated by the four nitrogens of the porpho-dimethene ligand and a chloride in the axial p~sition.'~ 3 Halogen Compounds An understanding of aluminofluoride and oxyfluoride melts is essential in the electrolytic smelting of aluminum as these are the precursors of fluoride glasses and are analogue systems for molten silicates. AI-27 NMR spectroscopy at high temperatures has been shown to provide important information about the species and their coordination numbers in aluminofluoride liquids as well as structural and dynamic changes in the crystalline fluoride^.,^ The thermal decomposition of [AIF,,,(OH),.(H,O)] depends strongly on the partial pressure of the gaseous reaction products and proceeds in three overlapping steps namely dehydration formation of amorphous A1203and metastable P-AIF, and formation of x-AIF and x-AI2O3. An exchange of F-and OH-also takes place. Whilst the main gaseous species are H,O and HF the gas phase complexes HAIF and H,AIF5 have also been observed.26 Of interest to writers of textbooks perhaps is the gas electron diffraction data recorded for GaCl and InCI, which is consistent with equilibrium structures of D,, symmetry and bond distances of rM-cl = 210.8(3) and 228.9(5) pm re~pectively.~' Bond energies and distances from the literature show that the M-CI bonds in MCI,, are stronger but longer than in MCI,(, for M = Al Ga or In.It was suggested that the relative weakness of the bonds in trivalent chlorides is due to the energy required to promote the Group 13 metal atoms from the 'P(s2p)ground states to 4P(sp2)valence states. The decreasing stability of trivalent relative to lower valency chlorides as the Groups are descended was associated with both increasing promotional energies and to decreasing M-CI bond strengths. TICI does not appear to exist in the gas phase. The first organic synthetic application mediated by Ga" as GaCI, has been described,' in a one-pot reductive Friedel-Craft type reaction; carbonyl compounds react with anisole to give alkylated anisoles in good yields. There has been a flurry of interest in complexes of In"' halides with various nitrogen and phosphorous based ligands.Thus the crystal structures of several 2,2'-bipyridyl complexes of InCI have been determined. The compounds [InCl,(bipy)(H,O)] [InCl,(bipy)(H20)].H20 and [InCl,(bipy)(EtOH)] are all Sac-octahedral. Lattice dimensions determined from powder data have been reported for another polymorphic modification of the [InCl,(bipy)(H,O)] complex.2" The six-coordinate indium complex [NHEt,][InCl,(dpt),] (Hdpt = 1,3-diphenyItriazene) has been reported.,' Reaction of Lewis bases L with the compound gives [InCl,(dpt)L,] L = py PEt, L = bipy phen dmpe or Et,PCH,CH,PEt,. The bidentate ligand adducts show a supramolecular architecture involving dipolar In-CI . . N interactions in the solid state. 24 M.O. Senge and K.M. Smith Z. Naturfbrsch.. Teil B 1992 47. 837. 25 J. F. Stebbins I. Farnan N. Dando. and S.Y. Tzeng J. Am. Ceram. Soc.. 1992 75 3001. 26 D. H. Menz. C. Mensing. W. Honk and H.G. Vonschnering Z. Anorq. Allq. Chern. 1992 611. 107. " A. Haaland A. Hammel. K.-G. Martinsen. J. Tremrnel and H. V. Volden. J. Chrm. Soc. Dalton Trans.. 1992 2209. " Y. Hashimoto K. Hirata N. Kihara M. Hasegawa and K. Saigo Trrrahrdron Lrrr.. 1992. 6351. 29 M.A. Malyarick S. P. Petrosyants and A. 9. Ilyuhin Polyhedron. 1992 11 1067. j0 J.T. Leman H. A. Roman. and A. R. Barron. J. Chrm. So(,.,Dalton Trans.. 1992 2183. AI Ga In and T1 The crystal structures of [In(bipy)Cl,(H,O)] [In(bipy)C1,(H,0)]~H20 and [In(bipy)C1,-(EtOH)]3' and of [InCl,(thiol),] complexes32 have been described.The first example of a trigonal bipyramidal type structure for an InI complex has been found in {p-[1,2-bis(diphenylphosphino)ethane]-1xP :2lcP')-bis[ 1,2-bis(diphe- nylphosphino)ethane]-1lcP,2lcP-bis[triiodoindium(r11)],and its crystal structure de- termined. The compound contains 1,2-bis(diphenyIphosphino)-ethaneligands bond- ing in two ways; firstly one ligand bridging between the two In atoms (bidentate) and secondly two ligands bonded to only one In atom each (m~nodcntate).~~ InI forms 1 1 adducts with various phosphine ligands [PR,; R = Bu', HPh, HBu; or H(cyclohexyl),]. Crystal structure on InI,.PHR (R = Ph or Bu') show the presence of four-coordinate indium atoms but also that intermolecular interactions (In-I-In P-H-I In-I-I-In) are present.Five-coordinate addition compounds of AH, that is AlI,L (L = acetone butanone cyclopentanone cyclohexanone benzal- dehyde and p-methylbenzaldehyde) have also been de~cribed.,~ The reactions between TIX (X = C1 Br or I) and substituted imidazoles { 2-met hyl-imidazole 2-phenyl-imidazole 2-ethyl-imidazole 1,2-dimet hyl-imidazole and 1 -methyl-2-phenyl-imidazole) have been studied and the complexes formed have been characterized. 36 The cis-hydride-chloride complex [(PP,)RuH(CI)] [PP = P(CH,CH,PPh,)J in CH,Cl has been found3' to extract the TIf ion from TlPF in the aqueous phase to give [(PP,)RuH(ClTl)]PF (Figure I) which contains a unique example of a TI' atom bonded to a C1 atom that acts as a bridging ligand; the crystal structure also shows pairs of these linked by a TIC1 bridge.Figure 1 4 Aqueous Solution Chemistry The bioinorganic chemistry and toxicology of All" in aqueous solution has been reviewed.,' This area of interest generates research into aqueous solution complexa- tion particularly with organic and bio-ligands relating to the purported link between Alzheimer's disease and aluminium. A1-27 NMR has been used in several studies of aqueous Al"' complexation by various ligands. With ascorbic acid a weak binary species AIL; together with two 31 A. B. Ilyukhin M. A. Malyarik. and S. P. Petrosyants Kristullogrufiyu 1992. 37. 663. 32 M.A. Malyarik A. B. Ilyukhin. S. P. Petrosyants. and Y.A. Buslaev Zh. Nrorg. Khim.. 1992. 37. 1504. 33 I. A. Degnan N. W. Alcock.S. M. Roe and M. G. H. Wallbridge Acfu Crystullogr..Sect. C 1992.48.995. 34 N. W. Alcock. I.A. Degnan 0.W. Howarth. and M. G. H. Wallbridge. J. Chem. Soc.,Dalton Truns. 1992 2775. 35 F.J. Arnaiz J. M. Bustillo and R. Lopez Synrh. React. Inorg. Metul-Org. Chem.. 1992 22 371. 36 M. R. Bermejo. M. I. Fernandez B. Fernaiidez. and M. E. Gomez. Synth. React. Inorg. Metul-Org. Chem.. 1992 22 759. 3 7 C. Bianchini. D. Masi K. Linn. C. Mealli. M. Peruzzini and F. Zanobini Inorg. Chem.. 1992. 31. 4036. 38 B. Corain. A. Tapparo. A. A. Sheikhosman. G.G. Bombi. P. Zatta. and M. Favarato Coord. Chem. Rev.. 1992 112 19; B. Corain. M. Nicolini P. Zatta ihid. 1992 112. 33. 28 J. P. Maher trinuclear mixed-hydroxo species [Al,(OH)4(H-1L)]3' and [A1,(OH)4(HlL)L]3f is formed.39 The coordination of Al"' and Ga"' with (+ )-(2R,3R)tartaric acid shows4' mononuclear 1 1 1 2 1 3 and dinuclear 2 :2 complexes with both octahedrally and tetrahedrally coordinated Al"'.The mononuclear 1 3 complex displays remarkable stability and symmetry owing to the formation of successive hydrogen bonds. Dinuclear di-tartrate-bridged complexes are favoured in tartrate solutions of Al"' and Gal1'. The chelated complex [Al(lactate),] dissolves in water to give stable acidic solutions where both free and metal-coordinated lactate ligands can be detected.41 Ligand exchange between metal-bonded and free lactate ligands was studied by H-1 NMR. At pH 7.5 the solutions are meta-stable slowly forming lactate and possibly metastable [Al(OH),(H,O),].The incorporation of fructose and of sucrose into an Al(OH) matrix has been investigated by various spectroscopic technique^.^^ Whereas fructose showed very good ability of binding to Al(OH), sucrose showed a much weaker binding tendency. A possible explanation is that fructose is bound to the Al(OH) matrix in p-pyranose and p-furanose forms but that sucrose is bound through its fructose part; in both adducts aluminium is octahedrally coordinated. An A1-27 NMR study of the binding of aluminium to the human serum proteins albumin and transferrin shows that approximately three A1"' ions are bound to each albumin.43 The albumin Al"' is octahedrally coordinated by oxygen atoms. However no recognizable signal was observed for Al"' bound to transferrin possibly because the bound Al"' exists in a site of low symmetry causing its NMR signal to be broadened by quadrupole-induced relaxation.Protanated chelates of Al Ga and In with propylene- diaminetetraacetic acid have been isolated and characterized by various methods.44 The ligand can be penta- or hexadentate. The A1 and Ga chelates appear to be isomorphous. The COOH is not ionized in the chelates. The stability constants for tris-bidentate chelates of 1-methyl-3-hydroxy-2-py-ridinone (mh,p) and 1,4-dihydroxy-2-pyridinone (dh,p) with Ga"' Al"' and In"' (also ~~111 GdlI1) have been determined.45 The proximity of the bidentate hydroxy oxygen donors to the pyridyl nitrogen atom of the ligand influences the 3 1 stabilities for each ion as the relative order of stability is dmhp > mh,p > dh,p (dmhp = 1,2-dimethyl-3-hydroxy-4-pyridinone).For these ligands the stability order is Fe"' > Ga"' > Al"' =-In"' > Gd"'. A low temperature H-1 and A1-27 NMR study of AI(CIO,) in aqueous mixtures of dimethylformamide and urea demonstrated that the Al"' is hexa-coordinated with monodentate binding from the oxygen atoms.46 In contrast to previous reports the A1-27 spectra for these solutions showed well resolved signals for the species [A1(H,0),-,L,]3+ (n = &6; L = dmf or urea) including two isomers for one of the wa ter-urea complexes. 39 L.O. Ohman and A. Nordin Acra Chem. Scund. Ser. B,1992 46 515. 40 F. R. Venerna J.A. Peters and H. Vanbekkurn Inorg. Chim. Acta. 1992.191 261 ihid. 1992. 197 I. 4' B. Corain B. Longato A. A. Sheikhosarn G. G. Bornbi and C. Macca. J. Chrm. Soc. Dalton Trans. 1992 169. 42 M. Tonkovic H. Bilinski and M. E. Smith Inorg. Chim. Acra. 1992 197 59. 43 S. Jernil A. Fatemi D. J. Williamson and G. R. Moore J. Inorg. Biochem.. 1992 46 35 44 S. B. Karweer 9.P. Pillai and R. K. Iyer fndiun J. Chem. Sect. A. 1992 30.1064. 45 E.T. Clarke and A. E. Martell Inorg. Chim.Acra 1992 1%. 185. 46 A. Fratiello V. Kubo-Anderson S. Azimi. C. Fowler E. Martinez R. Perrigan S. Shayegan and 9. Yao. Mayn. Reson. Chem.. 1992 30,280. Al Ga In and TI 29 The low temperature Ga-71 NMR spectra of aqueous solutions containing GaCI, C1- and Ga(CIO,) show4' clear evidence for the existence of octahedral complexes with mixed ligands [GaCl,(H,0),-,](3 -n)+.This is in contrast to the Raman spectra which only show signals of [GaCl,] -and [Ga(H20)J3 ions. + 5 Zeolites In order to help understand the chemical processes involved in the formation of gallosilicate zeolites alkyl-ammonium gallosilicates have been studied by using Si-29 and Ga-7 1 NMR in both aqueous and aqueous-dimethylsulfoxide solutions.48 Cyclic trimers a branched cyclic trimer and a double three-membered ring-anion with one incorporated Ga atom were observed. Due to the larger size of GaO unit compared to SO, gallosilicate anions with rather acute ( <90') SiO-Ga-OSi bond angles were found to be especially stable. Dimethylsulfoxide/water mixtures promote the forma- tion of ring silicate and gallosilicate anions.There was evidence for gallosiloxane (Si-0-Ga) bonds in some solutions. Aluminium has been replaced by gallium in zeolite b-frameworks and infrared measurements of the OH stretching band (3615-3625 cm- ')indicate that the Brernsted acid strength of the zeolites decreases as A1 is replaced by Ga in the frame~ork.,~ The gallium system is more effective at incorporating silicon than the aluminium system. Synthesis of the gallophosphate molecular sieve cloverite with a channel size of 20-tetrahedral-atoms has been described these zeolites are thermally stable and arc able to absorb large organic molecules.s0 Crystalline gallosilicates with a pentasil (MFI)framework containing Ga3' in lattice positions have been synthesized51 by the + hydrothermal technique using [Et,Bu"N] as template in the gel system Na,O :(Et,Bu"N),O :Ga,O :SiO H,O.A novel oxyfluorinated microporous gallophosphate [Ga,(PO,)(HPO,),F,(OH)~ C,N2H,,.0.5H,0] has been characterized. In this encapsulated 1,4-diazabicyclo C2.2.21octane (DABCO) acts as a template for synthesis.s2 6 Thallium-based Superconductors Though no more materials with exceptionally high values of T (the transition temperature to a superconductor) have been reported there is still great activity in this subject and a thallium compound T1,Ba,Ca2Cu,0,0 still holdss3 the record T, of 128K. Of possible relevance to the properties of the superconductors is the observation that thallic oxide-6 an oxide with high conductivity should be regarded as non-stoichiometric and deficient in oxygen.54 The single superconducting phase bulk 2234-type superconductor TI -x-Ba,Ca3 +xCu401 ,-8 was synthesized using a 2245-type composition in the precur- j7E.Brendler B. Thomas and S. Schonherr Monatsh. Chem.. 1992. 123 285. 4R R.F. Mortlock A.T. Bell. and C. J. Radke J. Phys. Chem. 1992 96 2968. 49 M.A. Camblor J. Perezpariente and V. Fornes Zeolites 1992 12 280. 50 Q. Huo and R. Xu J. Chem. Soc. Chem. Commun.. 1992 1391. '' S.V. Awate P.N. Joshi V. P. Shiralkar and A.N. Kotasthane J. Inch. Phenom. Mol. Recoyn. Chem. 1992 13 207. " T. Loiseau and G. Ferey J. Chem. Soc. Chem. Commun. 1992. 1197. " A.R. Armstrong and P. P. Edwards Annu. Rep. Prog. Chem.. Sect. C Phys. Chem. 1991. 88 259. 54 A.Goto H. Yasuoka. A. Hayashi and Y Ueda J. Phys. So<. Jpn.. 1992 61 1178. 30 J. P. Maher sor.' These show a T of 113K which can be increased by oxygen loading or by prolonged vacuum annealing to 1 16 K. Single phase bulk 2223-type samples were prepared T1 -x -,Ba,Ca +,Cu,O ~1' (0 < x < 0.4) whose structures are tetragonal. Thallium and oxygen deficiency was found; holes are due to Ca2+ substituting on the T13+ sites. The T was 112-1 18 K and was found to increase with increasing hole concentration. The origin of the holes for all these samples is due to Ca2+ substitution on the TI3+ sites.56 Similarly hole concentration and T were examined after synthesis of T1 -,Ba -,La,Cu06 -(0.00 < y < 0.35; 0.0 dz d0.2). During the oxygen annealing samples with y = 0.00 extruded thallium to form Tl,O and transformed from tetragonal to orthorhombic; samples with y = 0.35 did not extrude thallium.It was concluded that T1 extrusion to form Tl,O proceeds by an ordered removal of T1 until the Fermi energy falls below a mobility edge in the T1 6s band.57 Superconducting TI,-,CaBa,Cu,O can be prepared without impurity from the corresponding two T1-0 layer cuprate only when some TI deficiency is in~orporated.~' An X-ray structure determination of single crystals of 2201 -type thallium cuprate (T1,.,,Cu,,,,)Ba,Cu06 has been perf~rmed.,~ Various T,s were obtained up to 110 K. The TI atoms are partially replaced by Cu atoms and TI atoms and O(3) atoms linked with T1 are displaced from their symmetrical sites.A structure/properties correlation for 2201-type cuprate crystals was established. Not all of the thallium materials have high T values. Single crystals of (T1 .87Cu1 ,)Ba,06 + ,have been obtained6' by a CuO self-flux method. Composi- tions suggest substitution of Cu for TI; X-ray diffraction shows tetragonal symmetry. Site occupancy refinements indicate completely occupied Ba and Cu sites within the structure and displacements of the atoms in the T1,0 layers of this crystal. T is only 12.4K. A new series of 1222-type thallium-lead layered cuprate compounds (Tl,Pb)Sr,(Nd,Ce),Cu,O have been synthesized and characterized by X-ray powder diffraction.61 Their T is in the range 3MOK. 7 Metal-Metal Bonded Compounds Metal-metal bonds have been described between Group 13 compounds and a number of transition metal moieties.The ion [(,~'-1n)(Mn(C0>,),]~- formed by treatment of K,[Mn,(p-CO),(CO),,] with InCl, has an idealized pentagonal-planar coordination for indium (Figure 2); the reaction also yields an In,Mn cluster.62 The reaction between NaCo(CO) and R,GaCI with bulky alkyl groups gives6 the novel volatile Co-Ga complexes [(CO),CoGaR,(thf)] [R = CH,C(CH,), CH,Si(CH,),]. The Co-Ga bonds are highly reactive and rapidly cleaved by electrophiles or nucleophiles. The compounds may be used to generate intermetallic Co/Ga films by low-pressure MOCVD methods. 55 M. R. Presland J. L. Tallon P. W. Gilberd and R. S. Liu Physica C 1992 191 307. 56 M. Paranthaman M. Foldeaki and A. M. Hermann. Physica C 1992 192 161.5' M. Paranthaman A. Manthiram and J. B. Goodenough J. Mater. Chem. 1992 2. 317. " R. Vijayaraghaven J. Gopalakrishnan and C.N. R. Rao J. Mafer.Chem. 1992 2 327. 59 N. N. Kolesnikov V. E. Korotkov M. P. Kulakov R. P. Shibaeva V. N. Molchanov R. A. Tamazyan and V.I. Simonov Physicu C 1992 195 219. 6o R.S. Liu S. D. Hughes R. J. Angel T. P. Hackwell A. P. Mackenzie and P. P. Edwards Physicu C 1992 198 203. 6' Z. Y. Chen Y.Q. Tang Y. F. Li D. 0.Pederson and Z. Z. Sheng Mater. Res. Bull. 1992. 27 1049. 62 M. Schollenberger B. Nuber and M. L. Ziegler Angew. Chem. Int. Ed. Engl. 1992 31 350. 63 R.A. Fischer and J. Behm Chem. Ber. 1992 125. 37. AI Ga In and TI 31 Figure 2 In Tl[Fe(CO),(NO)] there are no TI-Fe or T1-TI covalent bonds rather discrete TI+ cations are well separated by [Fe(CO),(NO)] -anions in a distorted NaC1-like structure.64 The first indium-copper cluster [Ph,P][CU,In,(SEt),,] has been prepared by the reaction of [Cu(CH,CN),][PF,] with [Ph,P][In(SEt),]; its crystal structure shows an adamantoid framework reminiscent of the chalcopyrite structure of CUI~S,.~~ 8 Thallium(1) There have been several studies which involve the stereochemical behaviour of T1' ions and thallium lives up to J.B. A. Dumas' epithet -the ornithorhynicus of the elements! Two polymorphs are observed in complexes of TI' salts of the antibiotic lasalocid- A.66 One crystal form is a one-dimensional polymer [Tl+(lasalocid A-)In in which the TI+ is coordinated on one side to five oxygens of an ionophore molecule and on the other side to the phenyl ring of the neighbouring molecule however Tl+-phenyl q6-bonding is weak.The second form is a monomer [Tl+(lasalocid A-)I where the T1' ion is coordinated on one side to six oxygens of an anion ligand whereas the other side of the metal ion is uncoordinated and faces a nonpolar environment provided by hydrophobic alkyl groups of neighbouring molecules in the crystal structure. This is the first ionophore-metal complex that lacks three-dimensional nonpolar enclosure of the metal ion. TheT1'complexes[Tl([18]aneN,S4)]PF,and [T1([18]aneS,)]PF6 ([18]aneN,S = 1,4,10,13-tetrathia-7,16-diazacyclooctadecane, [18]aneS6 = 1,4,7,10,13,16-hexathia-cyclooctadecane) have been synthesized and their crystal structures determined.67 The complex structure of [TI([18]aneN,S4) PF shows the TI' ion occupying the 'cradle' formed by the macrocycle and bound uia an [N,S + S,] donor set; this leaves the top face of the metal centre exposed except for long-range interactions with two further thioether donor atoms from adjacent [T1([ 1 8]aneN,S4)] cations.In the complex + [TI([ 18]aneS6)]PF the structure shows TI' interacting with all six macrocyclic thioether donors with two of those interactions being considerably shorter than the other four. There are additional long-range interactions with two further thioether donors from adjacent [TI([ 18]aneS,)]' cations. There is also a long-range contact with one F atom of the PF counter-ion. Thallium(1) ethoxide has been found6' to cleave the ester of aspartane L-a-aspartyl-L-phenylalaninemethylester; a subsequent intramolecular cyclization gives T1'~3-benzyl-6-(carboxylatomethyl)-2,5-dioxopiperazine. The crystal structure shows that the T1' ions have four short and four long contacts to seven oxygen atoms and one nitrogen atom from a total of six neighbouring 3-benzyl-6-(carboxylatomethyl)-" L.M. Clarkson W. Clegg D. C. R. Hockless and N. C. Norman Acra Crystalloqr.,Sect. C 1992,48,236. 65 W. Hirpo S. Dhingra and M.G. Kanatzidis J. Chrm. Soc. Chem. Commun. 1992 557. " K. Aoki I.-H. Suh H. Nagashima J. Uzawa H. Yamazaki J. Am. Chem. Soc. 1992 114 5722. '' A. J. Blake G. Reid and M. Schroder J. Chem. Soc. Dalton Trans. 1992 2987. " P. Mikulcik P. Bissinger J. Riede H.Schmidbaur Z. Naturjorsch.. Tril B 1992. 47 952. J. P. Maher 2,5-dioxopiperazine anions. There are inter-anionic hydrogen bonds only between the imino groups and the carbonyl oxygen atoms a pattern similar to that found for cytosine-guanosine contacts in DNA. The 18-crown-6 complexes of thallium(1) 2- and 4-nitrophenoxide and of tcnq have been ~ynthesized.~~.~’ For the latter compound the TI+ lone pair has an active stereochemical role in the solid state. The new ternary phase TI3Al7S ,has been ~repared.~’ The polymeric anionic part of the structure can be described as a puckered layer-like arrangement of corner- sharing [AlS,]-tetrahedra parallel to the 001-plane. The aluminium-sulfur layers are connected via single sulfur atoms.These T1’ ions bridge the layers. The mean AI-S bond lengths are 2.227 8 for p2-S-Aland 2.298 A for p3-S-AI. The coordination of thallium is very asymmetric and the TI-S bond lengths vary from 3.009(9) to 3.907(9)& containing four short and two or three longer distances. A rather short TI. -T1 distance of 3.619(3) I$ is observed between two of the three crystallographically independent T1 atoms so that a weak bonding interaction is implied. The non-stoichiometric compound TI,Ti,Se has been found’ to crystallize in the hexagonal Nb,Se structure with TI atoms located in the hexagonal channels;72 the formal valence of the thallium atoms is clearly below + 1. The 2,2-dicyanoethylene- 1,l-diselenolate containing compound [AsPh,] ,[TI,- (Se,C=C(CN),),] has been prepared and characterized by single-crystal structure analysis.73 The complex is dimeric with a Se,Te octahedral centre and a TI-TI distance of 3.547(4) A.b9 L. R. Caswell J. E. Hardcastle T. A. Jordan I. Alam K.A. Mcdowell C.A. Mahan F. R. Fronczek and R.D. Gandour J. Inclus. Phenom. Mol. Recoyn. Chem.. 1992. 13. 31. ’O M.C. Grossel and S.C. Weston J. Chrm. Soc.. Chem. Commun.. 1992. 1510. ” B. Krebs and H. Greiwing. Z. Anorg. Allg. Chem. 1992. 616 145. ’’ W. Bensch and J. Koy Muter. Re.\. Bull.. 1992 27. 731. ” H.-U. Hummel. E. Fischer.T. Fischer. D.Gruss. A. Franke. and W. Dietzsch Chrm. Ber.. 1992,125 1565.