The Typical Elements PART 11 Group 111 By A. G. Massey 1 Boron A comprehensive collection of IlB n.m.r. data on compounds having boron atoms with co-ordination numbers 2 3 and 4 is contained in the book by Noth and Wrackmeyer.' Besides being useful to the spectroscopist the 96 tables in the review make an excellent starting point for a rapid general survey of known boron compounds. A characteristic feature of "B n.m.r. spectra is the broadness of the peaks a quality which greatly impairs resolution. Although it might be tempting to attribute these line widths (usually 10-100 Hz) to the short relaxation time of the quadrupolar B nuclei this is not a satisfactory explanation since measurements of "B spin-lattice relaxation times have demonstrated that the 'natural linewidth' due to quadrupolar relaxation is generally less than 10 Hz.Furthermore in an analysis of the "B n.m.r. spectra of B4H10 and BSHg it has been shown that unresolved B-B spin-spin coupling is not the sole source of the extra broadness as scalar relaxation and partially collapsed spin-spin multiplets also play a significant part in broadening "B n.m.r. lines. Complications due to the presence of loB in isotopically normal samples are also possible and hence "B-enriched compounds are necessary for an accurate analysis.2a From a study of single boron crystals obtained from the hydrogen-reduction of high purity boron tribromide on a tantalum wire at 1200 "C it is concluded that there is only one modification of tetragonal boron. The structure is based on a three dimensional boron skeleton very similar to that of a-A1B12 and contains simple (B12) and twinned (B21) icosahedra linked by isolated boron atoms.2b Crystalline boron reacts with S2C12 at 800-1000 "Cto give the unstable triatomic molecule chloro- thioborine ClB=S; the methyl derivative was formed in an analogous manner using dimethyl disulphide.2' Boranes and their Derivatives The degradation of pentaborane(9) using tri- methylphosphine in toluene at 25 "C leads to a 70% yield of the diborane(4) adduct B2H4,2PMe3.It is a white crystalline solid which sublimes slowly in a vacuum at room temperature. The synthesis is particularly interesting since it uses a com- mercially available b~rane.~ Irradiation of diborane(6) with the 973 cm-' line of a CO laser gives Bl0HI4 B5H9 B5Hll (BH), and hydrogen; no BZOH16 found by previous workers could be detected in any of the experiment^.^ The results are explained in terms of a thermal reaction.' A simplified preparation of decaborane( 14) using standard laboratory ' H.Noth and B. Wrackmeyer 'N.M.R. Basic Principles and Progress' Vol. 14 ed. P. Diehl E. Fluck and R. Kosfeld Springer-Verlag 1978. * (a) R. Weiss and R. N. Grimes J. Amer. Chem. SOC.,1978,100,1401;(b) M. Vlasse M. Boiret R. Naslain J. S. Kasper and K. Ploog Compr. rend. 1978,287,C,27;(c)C. Kirby H. W. Kroto and N. P. C. Westwood J. Amer. Chem. SOC.,1978,100,3766. R. K.Hertz M. L. Denniston and S. G. Shore Inorg. Chem. 1978,17 2673. S. Shatas D.Gregory R. Shatas and C.Riley Inorg. Chem. 1978.17,163. C.Riley S. Shatas and V. Arkle J. Amer. Chem. SOC.,1978,100,658. F. A. Hart A. G. Massey P. G. Harrison and J. H. Holloway apparatus and starting from sodium tetrahydroborate has been described. Boron trifluoride etherate is heated in diglyme to ca. 105"C under nitrogen with NaBH when the BllH14- anion is formed; oxidation of this ion with dichromate results in a 40% yield of B10H14.6 For many years it has been suspected that crude commercial decaborane( 14) contains small amounts of higher boron hydrides; these have now been identified as &OH16 and B2&6 using mass spectrometry.' A structure with 22 vertices probably represents the upper limit for stable closo boron hydrides.* Dietrich has refined his 1971 estimate of the charge distribution in decaborane(l4) arising from X-ray and neutron data and compared the new results with those calculated quantum-mechanically by Lipscomb.' MNDO calculations have been carried out on the known boranes up to BI0Hl6 and borane anions up to B12H122-.The results whilst confirming the tendency of MNDO to underestimate the strengths of three-centre bonds were in sufficiently good agreement with experiment as to suggest that the technique would prove useful in further studies of borane chemistry. lo Extended molecular orbital calculations have been used to follow the changes in electronic structure which occur when idealised borane polyhedra are synthesised from each other by capping faces and edges with single BH units or by mutual approach of two faces." The infrared and Raman spectra of cis and trans 1,2-dimethyldiborane have been measured assigned and a set of fundamentals proposed.It is suggested that Raman spectra can probably be used to obtain rough quantitative estimates of the various methylated diboranes present in mixtures. l2 Monobromo-and monoiodo-diborane can be made in high yield by condensing BX3 and B2H6 at -196 "C warming the mixture to 0 "Cand holding it at that temperature for three hours; separation of the products by fractional condensation and repetition of the cycle nine times leads to an 80% conversion of the dib~rane.'~ MNDO calculations on the hydroboration of alkenes indicate that the orientation of addition to the olefins is determined primarily by steric effects.A loose r-type complex is a marginally stable intermediate the formation of this being the rate- determining step for the overall reaction. Activation energies and heats of reaction for formation of the v-complexes show an unexpected increase in the order ethylene < propene < isobutene. The electronic effects of the methyl groups are apparently outweighed by the steric repulsions between hydrogen atoms of the borane and methyl groups. Acetylene and methylacetylene also react uia inter-mediate v-complexes but these are much more stable than those in the olefin hydroborations. It might even be possible to isolate the BH3,C2H2complex in matrices at low temperatures.14 The "F n.m.r. spectrum of B4HSPF2NMe2 at room temperature shows the presence of the exo and endo isomers.At very low temperatures hindered rotation 'G. B. Dunks and K. P. Ordonez J. Amer. Chem. Soc. 1978,100 2555. ' N. N. Greenwood J. D. Kennedy and D. Taylorson J. Phys. Chem. 1978,82,623. J. Bicerano D. S. Marynick and W. N. Lipscomb Znorg. Chem. 1978,17,2041. 9 H. Dietrich and C. Scheringer Actu Cryst. 1978 B34,54. lo M.J. S. Dewar and M. L. McKee Znorg. Chem. 1978,17,1569. l1 J. Evans J.C.S. Dalton 1978 18. D. F. Eggers D. A. Kohler and D. M. Ritter Spectrochim. Actu 1978 34A,731. l3 J. E. Drake B. Rapp C. Riddle and J. Simpson Znorg. Synth. 1978,18 145. l4 M. J. S. Dewar and M. L. McKee Znorg. Chem. 1978 17 1075. The Typical Elements occurs about the P-B bond in what is probably the endo i~omer.'~" An open hypho structure is s~ggested"~ for the fluxional molecule tetramethylethylene-diaminetetraborane(8).From mass spectrometric observations on a series of proton-transfer reactions B5Hi+ R + RH' +BsHg where R is a stable molecule of known proton affinity the proton affinity of the B5Hg radical is calculated to be 184f2 kcal mol-'. Combined with other known thermo- dynamic data this gives a value of 63.8k3 kcal mol-' for AH (B5Hg).16 The two isomerizations 1-ClBSHg +Et2O 2-ClBSHg +Et2O are both approximately first order in ClB5Hg and diethyl ether. The data suggest that the isomerizations occur via a boron cage rearrangement involving a Et20,ClB5Hg complex rather than a mechanism which involves B-Cl bond cleavage." In Me2SnB,,HI2 the dimethyltin group is bonded to the decaborane cage at edge boron atoms B5-B6 and B9-Blo by what can be regarded formally as two three-centre B-Sn-B bonds.The cleavage of the Me2Sn group by excess bromine results in the facially disubstituted 5,10-dibromodecaborane( 14). When Me2SnBlOHI2 is treated with a deficiency of bromine one of the products is MezSnBrBloH12Br showing that the reaction proceeds by stepwise cleavage of the B-Sn-B three-centre bonds in an oxidative cleavage reaction process l8 H H-@H .Br &Br Br MeSnMe Br2,QQH-@H .Br H The first facile and convenient hydroboration reactions involving a polyhedral borane have been described using 6-thia-nido-decaborane(ll).The site of attack is the exo B-H bond at the 9 Is (a)T.F. Moore A. R. Garber and J. D. Odom Inorg. Nuclear Chem. Letters 1978,14,45; (b)H.M. Colquhoun J. Chem. Res. (S) 1978,451. l6 Jia-Shen Wang A. J. DeStefano and R. F. Porter Inorg. Chem. 1978,17 1374. l7 D. F. Gaines and J. L. Walsh Inorg. Chem. 1978,17 806. '* T. J. Dupont R. E. Loffredo and R. C. Haltiwanger,Inorg. Chem. 1978,17 2062. l9 (a)B. J. Meneghelli and R. W. Rudolph J. Amer. Chem. Soc. 1978,100,4626; (6)I. A. Baidina N. V. Podberezskaya V. I. Alekseev V. V. Vokov and S. V. Borisov Zhur. strukt. Khim. 1978,547. F. A. Hart A. G. Massey P. G. Harrison and J. H. Holloway The structure of 6,9-bis(ammine)decaborane B10H12(NH3)2, is very similar to those of the acetonitrile and dimethylsulphide derivatives; the B-N distances are 1.598 and 1.591 A.196 Metal1oboranes.-The iron-bridged diborane(6) derivative K'[p -Fe(C0)4B2H5]-results as a dark brown solid from the reaction.20 H [ B',h J K2'[Fe(C0),l2-+3THF,BH3-+ K' H,'*** B**aHH,+KBH4+3THF(98%) (cob When iron pentacarbonyl and pentaborane(9) are added to LiAlH in diethyl ether a deep red solution and a dark precipitate are formed.Work up of the mixture yields unreacted starting materials B4HEFe(C0)3 and a yellow-brown very air-sensitive liquid identified as B2H6Fez(C0)6 and assigned structure (1)on the basis of infrared and n.m.r. spectral evidence.21 0 C P The U.V. photoelectron spectra of several ferraboranes including B,HEFe(C0)3 BsH9Fe(C0)3 and BSH3Fe(CO), have been reported. The spectrum of the latter is consistent with two carbonyl groups being in exopolyhedral positions (2).22The PE spectrum of B,HEFe(C0)3 calculated using SCF-Xa-SW MO theory and the experimental curve are in good agreement showing that a reasonable description of the electronic structure of this type of molecule can be obtained from a first- principles one-electTon treatment without recourse to configuration intera~tion.~~ 2-Berylla-nido -hexaborane( 1l),prepared via the reaction 1-ClBSH8+Be(BH& -P B2H6 +BeC12+B5HloBeBH4 possesses a pentagonal pyramidal cage structure in which one basal position is occupied by a beryllium atom.A terminal hydrogen is attached to each of the cage boron atoms and bridge hydrogens link all adjacent basal atoms in the cage; the BH group is attached to the beryllium atom by two bridging hydrogen atoms.Treatment of the compound with hydrogen bromide at -78 "C produces BsHloBeBr from which 2,2'-commo-bis[2-berylla-nido-hexaborane( 1l)]may be obtained in 40% 2o G. Medford and S. G. Shore J. Amer. Chem. SOC.,1978 100 3953. 21 E. L. Andersen and T. P. Fehlner J. Amer. Chem. SOC.,1978 100,4606. 22 J. A. Ulman E. L. Andersen and T. P. Fehlner J. Amer. Chem. SOC.,1978 100,456. 23 D. R. Salahub J.C.S. Chem. Comm. 1978 385. The Typical Elements 169 yield by reaction with an excess of CSB& at room temperature. The structure of Be(B5H10)2 consists of two pentagonal pyramidal cages linked by a common beryl- lium atom the dihedral angle between the basal plane of the two cages being 66°.24*25 An iron atom can be 0-bonded to a basal atom in the B5H9 structure via the reaction -40" C --+Fe(775-C5H5)(CO)2(2-B5H8) K+B5H8-+ Fe(~5-C5Hs)(CO)21 -100% The product is quantitatively deprotonated by potassium hydride to yield K+[Fe( q5-CsH5)(C0),(2-B5H7)]- which reacts smoothly with another equivalent of the iodide26 K'[Fe( 77 5-C5H5)(CO)2(2-B5H7)]-+ + Fe(q5-C5H5)(CO)21 Like its B5H9 analogue the cobaltaborane 2-( q 5-CSH5)CoB4H8 undergoes depro- tonation with sodium hydride at a bridging hydrogen adjacent to the cobalt atom closo -1,2477 5-C5HSCo)2B4H4 Irradiation of 2-(q 5-C5H5)CoB4H8 in the presence of iron pentacarbonyl produces 1,2,3-(q5-C5H5)2C02(CO),FeB3H3, which is thought to have an octahedral Co2FeB3 cage in which all the metal atoms occupy the same triangular The tetrametallic air-stable cluster compounds (q'-C5H5),Ni4B4H4 and (q5-C5Hs)4Ni4B5H5 are made by stirring a mixture of NaB5H8 nickelocene and sodium amalgam in THF and separating the products by chromatography.The former brown compound possesses a closo dodecahedra1 cage containing four nickel and four boron atoms.28 A number of cobalt and nickel arsaborane derivatives have been prepared e.g. piperidine ~,~-B~OH~OAS~ + C5H6+ CoC12 PC~H~CO(B~H~AS~) However the chemistry of arsaborane-transition-metal complexes is limited in direct contrast to the rich chemistry with many other heteroborane anions. It appears that when the heavier members of a given family of elements are substituted 24 D. F. Gaines and J.L. Walsh Znorg. Chem. 1978 17 1238. 25 D. F. Gaines J. L. Walsh and J. C. Calabrese Znorg. Chem. 1978 17 1242. 26 N. N. Greenwood J. D. Kennedy C. G. Savory J. Staves and K. R. Trigwell J.C.S. Dalton 1978,237. 27 R. Weiss J. R. Bowser and R. N. Grimes Inorg. Chem. 1978 17 1522. 28 J. R. Bowser and R. N. Grimes J. Amer. Chem. SOC.,1978,100,4623. 170 F. A. Hart A. G. Massey P. G. Harrison and J. H. Holloway into a borane cage both the percentage yield of products and the number of accessible compounds drop dramati~ally.~~" The "B n.m.r. spectra of nidu-heteroboranes of formula BloH12E (E = S Se Te As- AsR PR CNMe, CH- or BH2-) have been recorded and partially assigned. The common structure of these boranes is that of an icosahedron minus one apex group E being at position 7 of the open face.Their spectra are similar and typically the resonances occur as doublets with assignments (reading upfield) being B(5) B(2,3) B(8 ll),B(9 lo) B(1) and B(4,6). The resonance of B(5)-antipodal to group E-is most sensitive to changes in E the shielding of B(5) decreasing in the order E = CH->CNMe3>PR >AsR >As->S >Se >Te.29b Borane Anions Cations and their Derivatives.-The boron spin-lattice relaxation behaviour of solid NaBH and NaBD has been studied in the region of the structural transition using "B n.m.r. The results confirmed the first order nature of the transition which is associated with the ordering of adjacent BH tetrahedra. In the high symmetry phase the orientations of the tetrahedral ions are randomly dis- tributed among two possible configurations whereas below the transition tempera- ture an orientational macroscopic order is established all the tetrahedra in a plane perpendicular to the c axis tend to have the same configuration while the orientation alternates from one plane to the At 70 "C redistribution of ligands occurs in the reaction between Bu4NBH4 and Bu4NBC14 in benzene with the formation of BHC13- BH2C12- and BHC13- the composition of products depending on the ratio of reactants.The thermal stability of the anions decreases in the order BC1,->BHC1,->B&->BH2C12->BH3Cl- the latter decomposing readily to BH2C12- and B2H7- in benzene Gas phase "B and 'H n.m.r. spectra of beryllium bis(tetrahydrob0rate) show that only the monomer is present for which a linear B-Be-B skeleton was inferred.The 11 B n.m.r. spectrum of C5H5BeBH4 consists of a quintet of quartets due to "B-H and 11 B-9Be coupling (9Be has a spin of 1). In both these tetrahydroborates the hydrogen atoms of the BH4 groups undergo rapid internal exchange.31 When diethylaluminium hydride is treated with the appropriate ratios of alu- minium tris(tetrahydrob0rate) the liquid hydride species Al(BH4)2H and Al(BH4)H2 are formed. The former is the more stable but under vacuum both compounds disproportionate evolving A1(BH4) the residues becoming solid when the concen- tration of AlH units exceeds about 78 mol% . Bis(tetrahydroborat0)alane reacts slowly with diborane at 0 "C to produce aluminium tris(tetrahydrob0rate) and forms 1:l adducts Al(BH4)2H,L with ligands such as dimethyl ether and dimethyl ~ulphide.,~ Although it has been confirmed, that dimethylgallium tetrahydroborate results when trimethylgallium and diborane are mixed a better method of pre- paration is to treat dimethylgallium chloride with lithium tetrahydroborate in the absence of solvent at -15 "C.The compound decomposes at room temperature to 29 (a)J. L. Little and S. S. Pao Inorg. Chem. 1978,17,584;(b)W. F. Wright A. R. Garber and L. J. Todd J. Magn. Res. 1978 30 595. 30 (a)A. Trokiner H. Theveneau and P. Papon J. Chem. Phys. 1978 69 742; (b)L. V. Titov L. A. Gavrilova K. V. Titova and V. Y. Rosolovskii Izvest Akad. Nauk S.S.S.R.,Ser. khim. 1978 1722. 31 D. F. Gaines J.L. Walsh J. H. Morris and D. F. Hillenbrand Inorg. Chem. 1978 17 1516. 32 P. R. Oddy and M. G. H. Wallbridge J.C.S. Dalton 1978 572. 33 A. J. Downs and P. D. P. Thomas J.C.S. Dalton 1978 809. The Typical Elements 171 give gallium metal hydrogen boron trimethyl and methylated diboranes; a ther- mally stable adduct Ga(BH4)Me2,2NH3 which is probably ionic [GaMe2(NH3)2]C[BH4]- is formed with an excess of ammonia at -80 “C. The infrared spectrum of the gaseous tetrahydroborate is consistent with a C2,structure in which the gallium is linked to a bidentate BH group. The d and f transition metal tetrahydroborates reviewed last year by Marks and K~lb,~~ continue to attract a good deal of attention. Sodium tetrahydroborate in the presence of triphenylphosphine reduces a number of cobalt(~r)~’ and nickel(11)~~ compounds to M’ tetrahydroborates stabilized by phosphine ligands e.g.CoCl2+ NaBH4+ PPh3 + CO(BH,)(PP~~)~ NiCI2+ NaBH + PPh3 + [Ni(BH,)(PPh&]2 In hydrido(tetrahydroborato)bis(tricyclohexylphosphine)nickel(II) the nickel atom is co-ordinated by two trans cyclohexylphosphine ligands a hydride hydrogen atom and two bridging atoms of the BH ligand to give a deformkd trigonal bi~yramid.~’ Yttrium has a formal co-ordination number of 1 1 in tris(tetrahydroborat0)- tris(tetrahydrofuran)yttrium(III) where three boron and three oxygen atoms are at the corners of a distorted octahedron; one of the tetrahydroborate groups is bidentate and the other two terdentate. In the terdentate Y-BH interaction the tetrahydroborate ligand is slightly tilted from local C3 symmetry resulting in inequivalent Y -H bond lengths.The gadolinium analogue is isomorphou~.~~ The infrared and Raman spectra of tetrakis(tetrahydroborato)zirconium(Iv) in which all the BH groups are terdentate have been assigned.39 Co-ordination of the bidentate tetrahydroborate groups in (q5-CH3C5H4)2Hf(BH4)2 is markedly unsymmetrical with alternating long and short X-H bonds round the four-membered HfH2B rings. Even at temperatures down to -155°C the exchange of terminal and bridging hydrogen atoms in the BH units is rapid on the n.m.r. time scale.,’ Uranium(1v) tetrahydroborate readily forms complexes with ethers the stoi- cheiometry and structure of the products depending markedly on the ether used.With dimethyl and diethyl ethers 1 1 adducts are produced as green slightly volatile crystalline solids. The structures consist of infinite chains of alternating uranium and boron atoms joined by double hydrogen-bridge bonds the remaining tetrahydroborates are attached to the uranium by triple hydrogen-bridges. In the dimethyl ether adduct successive ether molecules along the chain are trans to each other whereas in the diethyl ether complex all the ethers are cis. The total co- ordination of the uranium is 14 made up of one ether oxygen and 13 hydrogen atoms. The average U-B distance is 2.53 and 2.89 A for triple and double bridges re~pectively.~~ A pale green 2 1 complex is formed with tetrahydrofuran and is 34 T. J.Marks and J. R. Kolb Chem. Rev. 1977 77 263. ” D. G. Holah A. N. Hughes B. C. Hui and C. T. Kan Canad. J. Chem. 1978,56,814. ” D. G. Holah A. N. Hughes B. C. Hui and C. T. Kan Canad. J. Chem. 1978,56,2552. 37 T. Saito M. Nakajima A. Kobayashi and Y. Sasaki J.C.S. Dalton 1978 482. ’* B. G. Segal and S. J. Lippard Inorg. Chem. 1978,17 844. 39 B. E. Smith H. F. Shurvell and B. D. James J.C.S. Dalton 1978,710;J. C. Whitmer andS. J. Cyvin,J. Mol. Strut. 1978 50 21. 40 P. L. Johnson S. A. Cohen T. J. Marks and J. M. Williams J. Amer. Chem. SOC.,1978 100 2709. 41 R. R. Rietz A. Zalkin D. H. Templeton N. M. Edelstein and L. K. Templeton Znorg. Chem. 1978,17 653. 172 F. A. Hart A. G. Massey P. G. Harrison and J. H. Holloway unique in being monomeric in the solid state.Distorted octahedral co-ordination of four BH4 groups and two THF molecules occurs around the uranium. The U-B distance of 2.56 8 is characteristic of triply bridging tetrahydroborates the twelve hydrogen atoms being placed at the corners of a hexagonal antiprism capped by the two oxygens of the THF m01ecules.~~ With di-n-propyl ether a dimeric 1 :1adduct is formed as a light green volatile solid. The dimer is unsymmetrical the uranium atoms occurring in two different environments. One uranium is bonded to oxygen atoms of two ether molecules and eleven hydrogens of four BH groups; the other uranium has 14 neighbours from five BH groups one of which acts as bridge to the first uranium atom.43 Tetrakis(tetrahydrob0rates) of the actinides protactinium neptunium and plutonium have been made by treating the tetrafluorides with aluminium tris(tetrahydrob0rate) AnF +2Al(BH4)3 + An(BH4)4+2AlF2BH4 An =Pa Np Pu The neptunium and plutonium compounds are dark coloured volatile liquids Np(BH4) being the most volatile Np'" derivative made to date.Pa(BH4) is an orange air-sensitive solid which sublimes in a vacuum at 55 oC.44a The tetrahydro- borate group in trisindenylthorium tetrahydroborate (qS-C,H,),ThBH3 acts as a terdentate ligand.44b The photoelectron spectra of Al(BH4)3 Zr(BH4), and U(BH4) have been recorded and discussed. It is suggested that doubly and triply bridged tetrahydroborates should have qualitatively distinct photoelectron spectra so that the technique may act both as a probe of electronic properties and as a diagnostic test for the mode of bonding of the BH group.44c N.m.r.spectroscopy shows that all the hydrogen and boron atoms in the octa- hydrotriborate anion B3H8- remain equivalent down to 137 K. A possible low energy pathway for the rapid tautomerization involves the conversion of the equilibrium double bridge structure to a single bridge structure followed by rotation of the BH3 group.45 Beryllium bis(octahydrotriborate) reacts with hydrogen chloride to give tetraborane with sodium cyclopentadienide to give C5H5BeB3H8 and with zinc dimethyl to form (CH3BeB3H&. In all three beryllium octa- hydrotriborate derivatives the B3Hs groups are bound to the Be atoms in a bidentate fashion and show a range of fluxional character when studied by variable-tempera- ture n.m.r.31 Electrolysis of octahydrotriborate salts in non-aqueous solvents containing tri- phenylphosphine leads to dissolution of the copper or silver anodes and the formation of the metalloboranes Cu(B3H,)(PPh3) and Ag(B3H8)(PPh3)3.46 42 R.R. Rietz N. M. Edelstein H. W. Ruben D. H. Templeton and A. Zalkin Znorg. Chern. 1978 17 658. 43 A. Zalkin R. R. Rietz D. H. Templeton and N. M. Edelstein Znorg. Chern. 1978 17,661. 44 (a) R. H. Banks N. M. Edelstein R. R. Rietz D. H. Templeton and A. Zalkin J. Amer. Chern. Soc. 1978 100 1957; (6)J. Goffart G. Michel B. P. Gilbert and G. Duyckaerts Znorg. Nuclear Chern. Letrers 1978,14,393;(c)A. J.Downs R. G. Egdel1,A. F. Orchard andP. D. P.Thomas,J.C.S. Dalron 1978,1755." I. M. Pepperberg D. A. Dixon W. N. Lipscomb andT. A. Halgren Znorg. Chern. 1978 17 587. 46 B. G. Cooksey J. D. Gorham J. H. Morris and L. Kane J.C.S. Dalton 1978 141. The Typical Elements Metathetic reactions of the general type L (C0)MX+ Me4NB3H8 -b L,MB3H8 + CO + Me4NX L = CO C5H5 PPh3; X = C1,Br I; B3H8bidentate have led to the preparation of a variety of octahydrotriborates of Mn Fe Re Mo and W. Bromine and chlorine react with (C0)4MnB3H8 to give (C0)4Mn(B3H7X) in which the halogen substitution has occurred on the boron not involved with bonding to the manganese.47 Decarbonylation of (C0)4MnB3H8 using heat or U.V. light results in the formation of (C0)3MnB3H8 which is the first reported complex containing a terdentate octahydrotriborate group; n.m.r.studies suggest that the Mn-H-B hydrogens are static whereas the B-H and B-H-B hydrogens appear to be exchanging rapidly.48 1,4-Dichloro-1,1,3,3-tetraphenyl-cutena-di(boraphosphane),BH2ClPPh2BH2-PPh2Cl is the unexpected product arising from the reaction of tetramethylam-monium octahydrotriborate and diphenylchlor~phosphine.~~ In (PPh3)*CuB4H9 which is the first metalla derivative of the B4H9- ion the copper atom serves as a vertex of the nido-cluster framework with no evidence of Cu-H-B bridge bonding.50 K+B4H9-+ (PPh3)3CuCI -+ (PP~~)~CUB~H~ Pentaborane(9) and hexaborane( 10) are quantitatively deprotonated in etherial solvents by potassium hydride to yield the corresponding conjugate bases B5H8- and B6H9-; by adding tetra-organophosphonium or arsonium salts to the solutions it is possible to isolate R4MB5H8 and R4MB6H9 derivatives.Of the eight salts studied those with the largest cation (R = C6H5) were found to be the most table.'^ Copper and silver complexes of nido -pentaborane anions result by adding the corresponding potassium salt to M(PPh,),Cl KB5H8 +Ag(PPh3)3Cl -b Ag(PPh3)2(P-BSHS) K[ 1-BrB5H7]+ CU(PP~~)~CI -1-BrB5H7) + CU(PP~~)~(~ The structure of CU(PP~~)~(~-B~H~) was determined last year and showed that the metal atom was 2,3-v2-bonded via three-centre two-electron bonds to the B5H8- cage. A gold complex possibly Au(PPh3)(B5H8) was formed at -78 "C but proved 47 D. F. Gaines and S. J. Hildebrandt Znorg. Chem. 1978 17,794. 48 S.J. Hildebrandt D.F. Gaines and J. C. Calabrese Znorg. Chem. 1978 17,790. 49 N.N. Greenwood J. D. Kennedy and W. S. McDonald J.C.S. Dalton 1978 40. K. E. Inkrott and S. G. Shore J.C.S. Chem. Comm. 1978,866. N. N. Greenwood and J. Staves J. Znorg. Nuclear Chem. 1978.40 5. 174 F. A. Hart A. G. Massey P. G. Harrison and J. H. Holloway to be too unstable to isolate.52 Similar reactions lead to the formation of palladium(I1) and platinum(I1) derivatives KB&+ cis-MX2L2-+ cis-M(B5H8)XL2+ KX X =C1 Br I or CH3;L = organophosphines or triphenylarsine The platinum complexes were the more stable and can be stored unchanged for long periods at room temperature; the trans platinum complexes made in the same manner appear less stable than the cis. In all cases the B5Hs ligand is q2-bonded to the metal atom uia the basal borons B(2) and B(3).530 The optimum conditions for the pyrolysis of tetraethylammonium tetrahydro- borate to (NEt4)2[B10H10] have been determined.Treatment of the BloHlo2- ion with strong acids in the presence of dialkylsulphides leads to the rapid formation of B10H12(R2S)2 in good yield. Starting initially from KBH the overall yield of B10H12(R2S)2 is about 45% .53b Potassium decahydro-closo-decaboratereacts at room temperature with anhy- drous hydrogen fluoride to give &OH14 and B18H22; salts of B12H1Z2- and BloCllO2- ions do not react. On the other hand the nido derivative CsB9H14 decomposed vigorously in liquid hydrogen fluoride to form caesium tetrafl~oroborate.~~ A number of routes to Bl2Hl1SH2- have been investigated; the most favourable synthesis was nucleophilic attack on B12H122- by N-methylbenzothiazole-2-thione followed by basic hydroly~is.~’ New products formed from mercapto undecahydro- closo-dodecaborate(2-) include mixed disulphides B12H11SSR2- where R is an organic group and the disulphide monoxide B12HllSOSB12Hl14-.The ion BllH14- can now be made in 62% yield uia a one step synthesis from sodium tetrahydroborate BF,,OEt,+BH,-+ BllH14-+BF4-+Hz+EtzO On addition of tetraethylammonium bromide to the mixture Et4N[B11H14] crystal- lizes BllH14- ions react with either NaHSeO or TeO in heptane-water to produce Bl1HllSe and BllHl ,Te respectively. These compounds are assumed to have closo nearly icosahedral cage structures since their “B n.m.r.spectra are very similar to the spectrum of the known BllHllS.57 All the boron atoms in the Bl1Hll2- anion are n.m.r. equivalent even at tempera- tures down to -70 “C. In theoretical studies of this fluxional behaviour it has been shown that the previously suggested C5,structure is not a viable intermediate or transition A low energy path for the rearrangement connects C and C2 structures but due to the small energy differences between C2,C1,and C2,it is not possible to decide which is the ground state ge~metry.~~ 52 N. N. Greenwood and J. Staves J.C.S. Dalton 1978 1144. ” (a) N. N. Greenwood J. D. Kennedy and J. Staves J.C.S. Dalton 1978 1146; (b) G. Guillevic J. Dazord H. Mongeot and J. Cueilleron J. Chem. Res.(S),1978,402. 54 V. V. Volkov and K. G. Myakishev Zzvest. Sibirsk Otdel. Akad. Nauk S.S.S.R.,Ser. khim. Nauk 1978 41. ” E. 1. Tolpin G. R. Wellum and S. A. Berley Znorg. Chem. 1978 17 2867. 56 G. B. Dunks and K. P. Ordonez Znorg. Chem. 1978,17 1514. 57 G. D. Friesen and L. J. Todd J.C.S. Chem. Comm. 1978,349. D. A. Kleier D. A. Dixon and W. N. Lipscomb Znorg. Chem. 1978,17 166. The Typical Elements 175 The 'resonance energies' of closo borane anions have been calculated by assuming that the three-centre bonds in each triangular face of the polyhedra interact in a similar fashion to the pmorbitals of carbon atoms in unsaturated hydrocarbons. Each molecular orbital of B,H,,- ions can thus be expressed as a linear combination of the three-centre BBB bonding orbitals and the MO calculations carried out in an analogous manner to the Hiickel method used in organic chemistry.The resonance energy of the as yet unprepared B,H,'- ion is zero suggesting it is not aromatic; on the other hand all the known closo anions have positive resonance energies and should be aromatic. The most symmetrical ion B12H122- has the greatest resonance ~tabilization.~' In Mg(BF30H)2(THF)4 prepared from boron trifluoride-tetrahydrofuranateand RMgBr where R is a bulky group the borate groups are co-ordinated to the magnesium uia their oxygen atoms. Other derivatives obtained include Mg(BF30H)2L3 Mg(BF30H)2L2 and Mg(BF30H)2L where L = NMe, NEt, pyri- dine or THF.60 Tetraethylammonium tetranitratoborate made by adding a slight excess of N204 to Et4NBC14 is an ionic solid in which the boron atom has distorted tetrahedral co-ordination to four unidentate nitrate groups; two OBO angles are 97.6" and the other four are 115.6°.6'" In N2H5'B(C~CH)4-,N21& the anion is almost perfectly tetrahedral and the N& molecule is hydrogen-bonded to the hydrazinium cation.616 The action of chlorosulphonic acid on potassium tetrafluoroborate in thionyl chloride produces the water-sensitive KB(S03C1) in which the boron atom is co-ordinated to one oxygen in each of the four S03Cl moieties.62 Condensation of boron tris(difluor0-oxosulphimidate) onto tetraphenylphosphonium difluoro-oxosulphimidate at -80 "C followed by a slow warm up to room temperature in the formation of tetraphenylphosphonium tetrakis(difluorooxosu1-phimidate Ph,P'[B(NSOF,),]-.The hydridotris( 1-pyrazoly1)borate group acts as a terdentate N-ligand in the complex methyl[hydridotris( l-pyra- zolyl)borate]tetraflu~roethyleneplatinum.~~~ Steric effects have been studied in the addition of trialkylboranes to lithium and sodium hydrides; the reactions proceed with 1 1stoicheiometry the products being trialkylhydroborates. An increase in the size of the alkyl group results in sharp decreases in reaction rate. For example with lithium hydride at 25 "C the rates are in the order Et3B > (Bu"),B > (Bu')~B >> (BuS)),B; even in refluxing tetrahydrofuran (BU')~B and other hindered organoboranes react only sluggishly and incompletely. Sodium hydride reacts with the unhindered and a number of the hindered organo- boranes at 25 "C; the other hindered boranes add rapidly in refluxing tetrahydro- f~ran.~~ Rather unexpectedly the corresponding addition of a dialkylborane (e.g.dicyclohexylborane or disiamylborane) to LiR (R = Me Bu or Ph) does not produce 59 Jun-ichi Aihara J. Amer. Chem. SOC.,1978 100 3339. 6o P. Paetzold W. G. Druckenbrodt and A. Richter Chem. Ber. 1978,111. 189. (a)0.A. D'yachenko L. 0.Atovmyan S. M. Aldoshin K. V. Titova and V. Ya. Rosolovskii Dokludy Akad. Nauk S.S.S.R. 1978,238,1132; (b) A. I. Gusev D. Y. Nesterov A. F. Zhigach R. A. Svitsyn and E. S. Sobolev Zhur. strukt. Khim. 1978 19 180. 62 G. Mairesse and M. Drache Acta Cryst. 1978 B34 1771. 63 (a)R. Eisenbarth and W. Sundermeyer Angew.Chem. Internat. Edn. 1978,17,212; (6)N. C. Rice and J. D. Oliver Acta Cryst. 1978 B34 3478. H.C. Brown S.Krishnamurthy and J. L. Hubbard J. Amer. Chem. SOC.,1978 100,3343. F. A.Hart A. G. Massey P. G. Harrison and J. H. Holloway LiR2R'BH; instead equimolar amounts of LiBR2R and LiR2BH2 are formed.65a The structures of two more complexes Mo(q 7-C7H7)[ q6-C6H5B(C6H5)3] and E~,N(MO(CO)~[~~-C~H,B(C,H~),~), have been determined in which a phenyl ring of the tetraphenylborate anion acts as a ?r-bonding ligand. In both compounds the distance of the molybdenum from the carbon bonded to boron is significantly longer than the other five Mo-C(pheny1) The formation of such ?r-complexes can lead to complications when tetraphenylborate is used as a precipitating coun- teranion due to loss of other ligands from the central metal atom.65c In Cu(en)- (CO)BPh, where en is 1,2-diaminoethane there appears to be a weak but significant interaction between the copper and two carbon atoms of one phenyl ring of the tetraphenylborate group; the Cu-C distances are 2.919 and 2.706 A.65d Cyanoborane complexes have been prepared by first treating sodium cyano- trihydroborate with one equivalent of halogen in monoglyme nNa[H3BCN] +! X2 + nNaX + (H2BCN) + H2; X = C1 Br or I 2 2 and then adding a Lewis base such as pyridine an amine or a phosphine to the cyanoborane polymer.When chlorine is bubbled through a moist benzene solution of pyridine-cyanoborane the B -H bonds are cleaved and py,BC12CN results.66" The structures of intermediates formed in the reaction of cyanoborates with carboxyl halides have been determined and shown to be either open chain or cyclic depending on the substituents.666 R' R' \/ 4O C C HO / \ / 'RZ B N H R" R' = cyclo-hexyl; / R2 = CF3.M+RiBCN-+ R'COX \ I R+N \\ RIB CR' 0' R' = cyclo-pentyl; R2 = phenyl. A convenient synthesis of boronium cations containing phosphine ligands has been described PPh Me2SBH3+I2 (one mole) -+ Me2SBHzI -PPh3BH21(92%) PPh3BH21+ L -P (PPh3)LBH2+I-L = PMe2Ph P(~ctyl)~ NMe3 PMe3 '' (a)J. L. Hubbard and G.W. Kramer J. Organometallic Chem. 1978,156,81; (b)M. B. Hossain and D. van der Helm Inorg. Chem. 1978 17 2893; (c) L. A. Oro E. Pinilja and M. L. Tenajas J.Organometallic Chem. 1978 148 81; (d) M. Pasquali C. Floriani and A. G. Manfredotti J.C.S. Chem. Comm. 1978,921. " (a)D. R. Martin M. A. Chiusano M. L. Denniston. D. J. Dye E. D. Martin and B. T. Pennington J. Inorg. NuclearChem. 1978,40,9; (b)P. R. Mallinson D. N. J. White A. Pelter K. Rowe andK. Smith J. Chem. Res. (S),1978 234. The Typical Elements When the iodide ion is replaced by hexafluorophosphate the boronium cations can be directly chlorinated to BHCl and BC12 derivative^.^^" The methyl groups in the boronium complex [H2B(PMe3)2]+Br- are metallated by butyl-lithium in THF to give lithium boratobis(dimethylphosphinomethy1ide) :67b Me2 Me2 v2 CH , PMe P-C\H /CH,-P \ *. MX Br- H2B +/\ + LiBu *H,B / Li(THF) AH,B / M BH 2 \ \ /\ / I' PMe P-CH P-CH CH2-P Me Me2 Me2 M =Zn Cd or Hg.Carbaboranes and Metallacarbaboranes-In carbaborane and metallacarbaborane chemistry a number of isomers are often encountered which can lead to difficulties in the isolation of pure products. However a technique little used by organometallic chemists reversed phase thin layer chromatography promises to be very useful in this respect. By impregnating cellulose plates with nujol and developing the chromatograms with methanol-water mixtures Plotkin and Sneddon have achieved the separation of several isomeric cobaltacarbaboranes from mixtures which had proved inseparable by other techniques.68a The photoelectron spectra of a number of the smaller carbaboranes68b and ferracarbaboranes22 have been recorded and by dividing each molecule into ring and polar fragments an empirical model was developed to rationalize the results.Alkaline methanolysis of 6-NMe3-6-CB9H1 at 60 "C has produced the first hypho-carbaborane. Hypho-3,4-p (trimethylaminecarba)hexaborane(1l),Me,N-CB,H is an analogue of BsHll in which the 3,4-hydrogen bridge has been replaced by a =CHNMe3 bridge.69 The 'direct' synthesis of metallocarbaboranes is an interesting new development in this field. The most basic method involves cocondensation of cobalt atoms cyclo- pentadiene pentaborane(9) and 2-butyne at -196 "C when [2,3-Me2-1,2,3-(q5- C5HS)CoC2B4H4] [2,3-Me2- 1,7,2,3 -(77' -C5HS)2C02C2B3H3],and [2,5-Me2- 1,7,2 5-(q5-CSH5)2C02C2B5H5] are formed. More simply heating together cyclo- pentadienylcobalt dicarbonyl pentaborane(9) and but-2-yne in a sealed tube gives rise to [5,6-Me2-1,8,5,6-(7 5-C5H,)2C02C2B,H,] and [1,7-Mez-3,5 1,7-(q5- C5H,),Co2C2B4H4] albeit in low yield.70" More thermally fragile compounds can be made by photolysis reactions like BC4HSFe(C0)3 which is produced by the short- time photolysis of cyclobutadieneiron tricarbonyl in the presence of pentaborane(9) and has a half-life of about one hour on the probe of a mass spectrometer held at 30 "C.The compound is assumed to be one of several possible isomers based on a pentagonal pyramidal structure.706 (a) B. T. Pennington M. A. Chiusano D. J. Dye E. D. Martin and D. R. Martin J. Znorg. Nuclear Chem. 1978 40 389; (6) H. Schmidbauer G. Muller U. Schubert and 0.Orama Angew. Chem. 1978 90 126. (a) J. S. Plotkin and L. G. Sneddon J. Chromatography 1978 153 289; (b) J. A. Ulman and T. P. Fehlner J. Amer. Chem. SOC.,1978 100 449. J. Duben S. Hermanek and B. Stibr J.C.S. Chem. Comm. 1978 287. (a)G. J. Zimmerman R. Wilczynski and L. G. Sneddon J. Organometallic Chem. 1978,154 C29; (b) T. P. Fehlner J. Amer. Chem. SOC. 1978,100 3250. F. A. Hart A. G. Massey P. G. Harrison and J. H. Holloway The triple-decker sandwich metallocarbaborane[p(2,3) -1,3-C3H4-1,7,2,3-(q5-C5H5)2C02C2B3H3] possesses a Co2C2B3 pentagonal bipyramidal cage in which the two carbon atoms are bridged by an exo-polyhedral propenylene group; the cobalt atoms are in the axial positions of the cage (3).'l The molecule {[5-[q5-C,H,)Co(q5- C5H4)][2,3-Me2C2B4H3]Co[2,3-Me2C2B3H5]} is a zwitterion composed of a [Me2C,B,H3]Co"'[Me2C2B3H5]- unit and a C5H5Co"'C5H4' group with the latter substituent attached to the closo portion of the metallocarbaborane system at B(5).C P14 c pi3 C (3) (Reproduced by permission from Inorg. Chem. 1978 17 10) (4) (Reproduced by permission from Inorg. Chem. 1978,17 1447) The metallocarbaborane structure consists formally of a cobalt(rr1) ion face-bonded to a pyramidal C2B4 and a cyclic C2B3 ligand; i.e. the cobalt atom is common to both an open and a closed polyhedral system (4).'2 " J. R. Pipal and R. N. Grimes Znorg. Chem. 1978 17 10. J. R. Pipal W. M. Maxwell and R. N. Grimes Znorg. Chem. 1978 17 1447. The Typical Elements Platinum can be substituted onto a carbaborane cage via the reaction RR c-c /'A\ HB -BH -BH nido-2,3-R2-2,3-CzB,H,+ Pt(PEt,) -+ I I PEt, H-BH-J / ,Pt \ P H Et 3 (5;R = H) (6; R = Me) the carbaborane cage has the geometry of a nido-pentagonal pyramid.Holding (5) at 100"Cfor three days results in the formation of a closo pentagonal pyramidal cage in which the platinum is at an apex and the carbon atoms are in positions 2 and 4. A similar structure is formed when (6)is heated to 100"Cexcept that the carbon atoms remain coupled together in the 2,3-positions (7).73 (Reproduced from J.C.S. Chem. Comm. 1978 169) 73 G. K. Barker M. Green T. P. Onak F. G. A. Stone C. B. Ungermann and A. J. Welch J.C.S. Chem. Comm. 1978 169.F. A. Hart A. G. Massey P.G. Harrison and J. H. Holloway (7) (Reproduced from J.C.S. Chem. Comm. 1978 169) Oxidation of the nido-7,8-C2B9Hll-ion using aqueous ferric chloride is known to yield nidu- 5,6-C2BsH12; the reaction has been repeated and the by-products separated by chromatography on silica gel identified as 5,6-C2BsHl10H 5,6-C2B8HIlC1,and nido-4,5-C2B7Hll. Yields of the latter rare carbaborane can be substantially increased by using concentrations of reactants in the range 0.1-0.2 moll-’; the pure compound is spontaneously inflammable in air.74 Dicarbadodecaborane-thallium derivatives can be made either by the straight- forward reaction7’ RC-CLi RC-C \ / 1 \ / + TICI -[ ,TIC1 R=Hor CH2Cl BIOH, BIOH or by direct thallation using thallium(II1) trifluoroacetate when substitution occurs at the B(9) HC-CH HC-CH \ / + TI(OOCCF,) -\ /-9-T1(00CCF3)2 B,oH,o Blob 74 H.M. Colquhoun T. J. Greenhough M. G. H. Wallbridge S. Hermanek and J. Plesek J.C.S. Dalton 1978,944. 75 V. I. Bregadze A. Y. Usyatinskii and N. N. Godovikov Doklady Akad. Nauk S.S.S.R. 1978,241,364. ’‘ V. I. Bregadze V. T. Kampel A. Y. Usyatinskii and N. N. Godovikov Izvest. Akad. Nauk S.S.S.R. Ser. khim. 1978 1467. The Typical Elements The mercurials bis( 1,2-dicarbadodecaborane-9)mercuryand bis( 1,7-Dicarbado- decaborane-9)mercury promise to be useful precursors to other B(9)-substituted derivatives e.g. HC -CH [Hcqoca2 9-Hg + TI(COOCCF,) -+ \ /-hoH9 9-T1(00CCF3)2 (ref. 76) HC-CH \ /-g-HgClBIOH9 + Pt(PPh,) -+ HC-CH \ /-BlOH9 9-PtCl(PPh,) (ref.78) When the mercury is bound to carbon however reaction with tris(tri- pheny1phosphine)platinurn results in the formation of Pt-Hg bonded derivative^.'^ PhC-C(CH,) HgX + Pt ( PPh ,I3 -* PhC-C (CH,), HgPtX( PPh,) \/ \/ BlOHlO B,oH,o n =Oor 1 X=ClorBr The molecular conformation of 1-(met hy1mercury)- 2 -(chlorome t hyl) -1,2 -dicarba- dodecaborane(l2) is distorted so that the chlorine is near to the mercury atom the Hg-..Cl distance being 3.27 A.79 ‘Heterocycles’ containing 1,2-dicarbadodecaborane(12) residues have been made via reactions of the type8’ H,C-C‘-‘C LiC-C-(CH,) -C\ -/CLi + Me,SiCI -I \.\/ /%Me BIOHlO BIOHIO H2C-C-C \/ BIOHIO Several rneso-tetracarbaboranylporphyrins including those derived from 1,2-C2B10H1 -1-CH2-1,2,-C2B10H1 and -1-CH2-2-CH3-1,2-C2BloHlo, have been described and were mainly made by Rothemund condensation reactions.81a Substitutionof the boron atoms in 1,2-dicarbadodecaborane(12) with aryl groups has been achieved by reducing the carbabcrane with sodium to the nido-dicarba- dodecaborate(l4) dianion treating this ion with either ArMgX or ArLi and then 77 L.I. Zakharkin and I. V. Pisareva Izuest Akad. Nauk S.S.S.R.,Ser. khim. 1978 1226;V. I. Bregadze V. T. Karnpel and N. N. Godovikov J. Organometallic Chem. 1978 157 C1. ’’ L. I. Zakharkin and I. V. Pisareva Zzuest Akad. Nauk S.S.S.R. Ser. khim. 1978 252. 79 N. G. Bokii Yu. T. Struchkov V. N. Kalinin and L. I. Zakharkin Zhur. srrukt.Khim. 1978,19 380. L. I. Zakharkin and N. F. Shernyakin Zzvest Akad. Nauk S.S.S.R. Ser. khim. 1978 1450. 81 (a)R. C. Haushalter and R. W. Rudolph J. Amer. Chem. SOC. 1978,100,4628; (b)V. N. Kalinin N. I. KobeI’Kova A. V. Astakhin A. I. Gusev and L. I. Zakharkin J. Organometallic Chem. 1978 149 9. F. A. Hart A. G. Massey P. G. Harrison and J. H. Hulluway oxidising the intermediate product with copper(I1) chloride. In this way a mixture of 3- 4- 8-and 9-aryl-1,2-dicarba-closo-dodecaboranes is obtained which may be separated by g.1.c.; the structures of 1,2-Me2-9-Ph-1,2-C2BloH9 and 4-(p-tolyl)-1,2- C2B10Hl were determined and confirmed their clusu-icosahedral nature.81b Dicarbadodecaborane(12) has been bound to a rigid matrix of polystyrene by reaction of 1-Li-1 ,2-C2B10Hll with the chloromethylated copolymer C6H.5 @-CHzCI+ LiC2B loHl -@-CH2CZB10H1 + LiCl Degradation of the cage using piperidine in benzene followed by addition of tris(tripheny1phosphine)rhodium chloride produced a useful hydrogenation catalyst active at about 100 atmospheres of H2:82 (PPh3)RhCI @-CH2C2B10H1 + @-CH2C2B9Hll-@-CH2C2B9HloRh(H)(PPh3)2 A general method of preparing mercaptoheteroboranes involves treating the heteroborane with sulphur in the presence of aluminium tri~hloride~~ AICI 1,2-C2B10H12+S -8-HS-1,2-CzBloHl1 e.g.- AICl ,2-CoC2B9H1 + S 8-HS-3-(q5-C~H&3,1,2-CoC2B9H1~ 3-(v5-CSHS)-3,1 By-products in the latter reaction include the sulphide disulphide and trisulphide S,(1,7-C2B10H11)2,x = 1,2,3.The HS-group can also be replaced by -SMe SMe2' and -SOMe.84" Four of the 71 possible isomers for a compound of formula C2B9H1,-SMe2 have been isolated. Selective degradation of 1-MeS- and 9-MeS- 1,2-C2B10Hll using KOH in the presence of methanol followed by addition of methyl iodide produces the 7-Me& and 5-Me2S-7,8-C2B9Hll derivatives respec- tively. Two further isomers 9-Me2S-7,8-C2B9Hll and 8-Me2S-7,9-C2B9Hll result from the treatment of the 7,8- and 7,9-C2B9HI2 anions with dimethyl sulphoxide. The structures of these nido-carbaboranes are based on an icosahedral cage which has had one vertex removed the two carbon atoms being on the open A new series of 12-atom nidu- heterocarbaboranes Me3NCBloHloPR have been produced by treating BlOHI2CNMe3 first with triethylamine and then with RPC12 (R = Me; Et; Ph).The structure of the derivative with R = phenyl has been solved and shows that the PPh unit bridges boron atoms B(9) and B(10) in the open face of the Bloc icosahedral fragment; the CNMe group occupies position 7 of the '' E. S. Chandrasekaran D. A. Thompson and R. W. Rudolph Znorg. Chem. 1978,17 760. '' J. Plesek and S. Hermanek CON.Czech. Chem. Comm. 1978 43 1325. 84 (a)J. Plesek Z. Janousek and S.Hermanek Coll. Czech. Chem. Comm. 1978,43,1332; (b)J. Plesek Z. Janousek and S. Herrnanek Coll. Czech. Chem. Comm. 1978 43 2862; (c) W.F.Wright J. C. Huffman and L. J. Todd J. Organometallic Chem. 1978,148 7. The TypicalElements Lithium 1,2-dicarbadodecaboranyldithiocarboxylate reacts with L2MC12 complexes of the nickel triad to form derivatives in which the dithio ligand is either monodentate or bidentate RC-C-CS2Li +L2MC12 + LM(S2CC-CR)Z +L2M(S2CC-CR)Z \i \I \I BlOHlO BlOHlO BlOHlO M = Ni Pd or Pt; R = Me; PhL = tertiary phosphine The tendency to farm bis(phosphine) adducts increases in going from Ni to Pt and also appears to depend on the type of co-ordinated phosphine.Five-co-ordinate structures are assigned to LNi(S2CC2Bl0HloRj2 in which and L2Ni(S2CC2BloHloR)2 the dithio ligand exhibits bidentate and unidentate-bidentate modes of bonding respectively. On the other hand four-co-ordination is attained in the bis(phosphine) adducts of palladium and platinum through unidentate co-ordination of the dithio ligand.A rapid intramolecular interchange between the uni- and bi-dentate dithio ligands occurs at room temperature in LPd(S2CC2BloHloR)2.85 Treatment of the [q5-C,H,)CoCB7H,]-anion with NiBr2,2glyme in the presence of C5H5- leads to polyhedral expansion and the formation of several isomers of (CSH5)2NiC~CB7H8 containing formally Ni'" and Co"' atoms. One of these isomers [2,3-di-q 5-cyclopentadienyl- 1O-carba-2,3-(nickelacobalta)decaborane(8)] has the bicapped square antiprismatic geometry expected of a 10-vertex CEOSO cage. The two metal atoms were indistinguishable and occupied adjacent vertices 2.449 A apart in the same equatorial belt (8). Thermal rearrangement to give an isomer with non-adjacent metal vertices does not occur at temperatures up to 450 0C.86 CP9 3 CP (8) (Reproduced by permission from Inorg.Chem. 1978,17,1662) B. Longato F. Morandini and S. Bresadola Inorg. Chim. Acta 1978,26,157. G.E.Hardy K. P. Callahan and M. F. Hawthorne Inorg. Chem. 1978,17 1662. F. A. Hart A. G. Massey P. G. Harrison and J. H. Holloway (Reproduced by permission from Inorg. Chem. 1978 17 1658) Polyhedral expansion of [2-(q '-C5H5)-2-Co- 1,6-C2B7H9] in the presence of FeCl and C5H5- produced the 1 1 -vertex compound [l,8-di-q5-cyclopentadienyl-1-ferra-8-cobalta-2,3-dicarbaundecaborane(9)]. Although one electron short of the ideal 2n +2 electrons for closo-polyhedral bonding this molecule has closo-octadeca- hedral geometry with the iron atom in the six-co-ordinate vertex the two carbons at four-co-ordinate vertices and the cobalt atom at a five-co-ordinate position but not adjacent to the iron.The iron-boron distances are significantly longer than the cobalt-boron bonds probably due to the greater co-ordination number at the iron atom (9).87 The anion in tetramethylammonium [1-q'-cyclopentadienyl-1 -ferra-2-carbaun- decaborate(-1)] is an 11-vertex polyhedron where nine boron atoms and one carbon atom form a decaborane-like framework with six of the cage atoms bonded to the iron. The carbon atom occupies a vertex of lowest co-ordination being bonded to only four other polyhedral atoms; B(3) occupies the other low co-ordination position and this is reflected in the Fe-B(3) bond length of 2.012 8 [mean Fe-B(other) is 2.252 A] (lo)." A comparative molecular orbital study of ferrocene and [l-(q5-CSH5)-1,2,3-FeC2B9H,1]-has shown that while the bonding in ferrocene involves primarily the 7r orbitals of the C,H5 ring that of the dicarbollide (C2B9Hl12-) complex involves the u orbitals of the open pentagonal face in an important role.In both molecules the HOMO'Shave very high dz2~haracter.~~ Oxidative addition of 7,9- and 7,8-C2B9HI2- to (PPh3),RuHC1 produces [2,2- (PPh3)2-2,2-H2-2,1,7-RuC2B9Hll] (11)and [3,3-(PPh3)2-3,3-H2-3,1,2-R~C2BgHll] 87 K. P. Callahan A. L. Sims C. B. Knobler F. Y. Lo,and M. F. Hawthorne Inorg. Chem. 1978,17,1658. 88 V.Subrtova A. Linek and J. Hasek Actu Cryst. 1978,B34,2720. 89 D.A.Brown M. 0.Fanning and N. J. Fitzpatrick,horg. Chem. 1978,17 1620. The TypicalElements U (10) (Reproduced by permission from Actu Cryst.1978 B34,2720) (12) respectively; both complexes may be regarded as seven-co-ordinate formally Ru'" compounds. Compound (11) reversibly eliminates one mole of hydrogen on heating in a vacuum to give the five-co-ordinate formally Ru" derivative 2,2-(PPh3)2-2,1,7-Ru(C2B9Hll). Both (11) and (12) readily lose hydrogen in their reactions with hydrogen chloride and carbon monoxide (11)+HCl + 2,2-(PPh3)2-2-H-2-C1-2,1,7-R~C2BgHll (11)+CO + 2,2-(PPh3)2-2-CO-2,1,7-R~C2B9H11 A pyridine complex [3,3-(PPh3)2-3-H-7-CsHsN-3,172-RuC2B9Hlo] was also pre- pared the pyridine being bonded to a boron atom on the pentagonal face adjacent to the ruthenium." The full paper describing the preparation and structure of [3-diethyldithiocar- bamato-172-dicarba-3-auradodecaborane( 1 l)] has now appeared." In the complexes {3-[C2H4(NMe2)2]-3,1,2-PdC2B9Hll} (13) and [3,3-(PMe&3,1,2-PdC2B9H11](14)there is a marked influence of the ligands trans to the C2B9Hll cage in that (13) has a slipped configuration whereas (14) has much more symmetrical metal-cage binding.Since tetramethylethylene diarnine is a u-donor and tri- methylphosphine is a moderate .rr-acceptor these results provide strong support for 9" E. H. S. Wong and M. F. Hawthorne Znorg. Chem. 1978 17 2863. H.M. Colquhoun T. G. Greenhough and M. G. H. Wallbridge J.C.S.Dalton 1978 303. F. A. Hart A. G. Massey P. G. Harrison and J. H. Holloway (2 n W (14) (13 and 14 Reprinted with the author’s permission from J.C.S.Chern. Comm. 1978 322) The Typical Elements the idea that .rr-acceptor ligands reduce the anti-bonding character and thus the effect of the occupied 5e1~py)-dy,* orbital which is perpendicular to the PdL2 plane and responsible in part for deviations from the regular closo geometry observed in many d8 metallocarbaboranes. Stronger vacceptors than PMe3 on the palladium should thus give rise to eveh more symmetrical stu~tures.~~ Rather unexpectedly 3,3-(PEt,),-3,1,2-PtC2BgHll, although having a virtually identical C2B9Hllcage and similar ligands to the above Pd-PMe complex has a much less symmetrical metal-cage interaction. The structure is that of a highly distorted icosahedron in which the platinum has slipped markedly towards B(8)and the CzB3metal-bonded face folds across B(4)...B(7)away from the metal (15).93 (15) (Reproduced from J.C.S.Dalton 1978 1363) Polyhedral expansion of [3,1,2-(q5-C5H5)FeC2B9Hll] has led to the preparation of the 13-vertex polyhedral [4,5-(q5-CsHs)2-4,5-Fe2-2,3-C2B9Hll] (16) which contains two formally Fe''' atoms and is thus electron deficient. Unexpectedly it also proved to be diamagnetic even though the iron atoms are about 3.20 8 apart and thus not directly bonded; the diamagnetism was assumed to be the result of spin pairing by interaction of the two iron atoms through the carbaborane ligand. The complex was also unusual in that the lowest co-ordination position in the cage was 92 H. M. Colquhoun T.G. Greenhough and M. G. H. Wallbridge J.C.S. Chem. Comm. 1978,322. 93 D. M. P. Mingos M. I. Forsyth and A. J. Welch J.C.S. Dalton 1978 1363. F. A. Hart A. G. Massey P.G. Harrison and J. H. Holloway occupied by a boron and not a carbon atom. Another product of the polyhedral expansion reaction was the ion [C5H5FeC,B9Hl1FeC2B9Hll] in which a C5H5 ring of (16)has been substituted by a 1,2-C2B9HIl2- ligand.94 Tetracarbon 12-vertex cages have been obtained by fusion together of dicar- or bon carbaboranes. When [closo-1,2,3-(C5H5)CoC2B4H6][nido-1,2,3-(C5H5)CoC2B3H7] are treated with 10% alcoholic potassium hydroxide in the air fusion occurs to create either C5H5CoC4B7Hll or three isomers of (C5H5)2C02C4B6H10. The structure of one of the latter isomers was determined and showed the gross geometry was that of a 13-vertex closo polyhedron with one vertex eliminated to create a six-membered open face containing the four carbon atoms.The two cobalt atoms were located in different types of co-ordination sites one being (Reproduced by permission from J. Amer. Chem. SOC.,1978 100 5045) linked to six other framework atoms and the other to only five atoms (17).95 The red air-stable [( 75-C5H5)Co(CH3)4C4B,H,0Et] formed by reaction [Me2C2B4H4]2FeH2with cobalt chloride and cyclopentadiene in ethanolic KOH at 70 "C has a novel structure resembling a severely distorted icosahedron whose two halves have been partially separated creating a huge opening on one side ( 18).96The iron atoms in the 14-vertex [1,14,2,5,9,12(~~-C~H~)~Fe~(CH;)~C~B~H~] occupy the two high-co-ordination positions at opposite ends of the molecule; the four cage carbon atoms are arranged in staggered fashion in the two equatorial rings such that the mutual C-C separations are maximized.The two C5H5 rings are planar unlike the Me2C2B4H4 rings which have their two carbons drawn slightly out of plane in the direction of the other ring; all four rings are parallel to within 1" (19).97 Boron Halides.-The preparation of boron tribromide from potassium tetrafluoro- borate and aluminium tribromide has been considerably improved. By preparing the aluminium bromide in situ and having a KBF :A1Br3 ratio of about 1:10the yield of boron tribromide can be pushed to over 80% making the method suitable for the synthesis of "BBr3 from K'oBF4.98The direct synthesis of boron tri-iodide has been 94 C.G. Salentine and M. F. Hawthorne Znorg. Chem. 1978 17,1498. 95 K.S. Wong J. R. Bowser J. R. Pipal and R. N. Grimes J. Amer. Chem. Soc. 1978 100 5045. 96 J. R. Pipal and R. N. Grimes J. Amer. Chem. SOC.,1978 100,3083. 97 J.R. Pipal and R. N. Grimes Inorg. Chem. 1978 17,6. 98 H.Noth and R. Staudigh Chem. Ber. 1978 111,3280. The TypicalElements CP5 CP4 (Reproduced by permission from J. Amer. Chem. SOC., 1978,100,3083) studied in a Pyrex closed-tube reactor in the temperature range 600-1000 "C the boron being selectively heated by means of an image furnace.99 Passage of boron tri-iodide through a heated silica tube at 840-900 "C gives a-rhombohedra1 boron.100 Mixed boron trihalide adducts are the subject of a recent review containing 189 references.*" Using electron diffraction data estimates of the barrier to internal rotation in the trimethylamine complexes of boron trifluoride and trichloride have been given as ca.6.2 kcal for BF,NMe and ca. 13.7 kcal for BCl,,NMe,.''* Tetramethylethylene diamine (TMED) forms a highly insoluble complex TMED,2BF3 when treated with boron trifluoride-etherate; since the air-stable monoalkylborane complexes TMED,RBH and TMED,2RBH2 react rapidly with BF releasing the RBH2 it has been suggested that these TMED complexes may be a 99 J. Cuelleron and J. C. Viala J. Less-Common Metals 1978 58 123. '('O C. Brodhag and F. Thevenot Compt. rend. 1978 286 C 229.lo' J. S. Hartman and J. M. Miller Adv. Inorg. Chem. and Radiochem. 1978 21 147. M. Hargittai and J. Brunvoll Inorg. Chim. Acra 1978,31 L379. F. A. Hart A. G. Massey P. G. Harrison and J. H. Holloway CP!5 cpll CAZ CP144 CR43 CP145 R42 CPl41 (19) (19 Reprinted with permission from Inorg. Chern. 1978 17 6. Copyright by the American Chemical Society.) useful way of storingmonoalkylboranes.'03Fr0me.s.r. studiesat 77 Kon y-irradiated trimethylphosphine and triphenylphosphine adducts of the boron trihalides 'it is thought that R3PIBX3+ions are formed where a single electron resides in the P-B u 0rbita1.l'~ Like methyls of the other Group IV elements tetramethylsilane acts as a high- yield methylating agent for the boron trihalide~.''~ SiMe4+BX3 4 Me3SiX+MeBX2 X = Br or I 2SiMe4+BX3 -+ 2Me3SiX+Me2BX Diboron tetrafluoride and tetrachloride add to the double bonds of methyl- enecyclopropane and vinylcyclopropane forming the diboryl compounds (20) and (21) respectively.The C-C bonds of the cyclopropane rings are not cleaved even when an excess of diboron tetrachloride is used.lo6 bCH + B2X4 -wCHzBX2 BXZ (20) C>-CH=CH~ C>-CH(BX,)-CH,-BX~ + B~X.,--* (21) A break-through has been achieved in the chemistry of the-boron monochlorides. B. Singararn and J. R. Schwier J. Orgunomerullic Chem. 1978 156 C1. '04 M. C. R. Syrnons and J. E. Drake J. Chem. Res. (S) 1978 122. lo' W. Haubold A. Gemmler and U. Kraatz Z. Nuturforsch. 1978 33b 140. W. Haubold and K.Stanzl Chem. Ber. 1978 111,2108. The Typical Elements Addition of 9 equivalents of S02C1 to (NBu4),B9H9 at -78 "C results in good yields of (NBu4),B9C19; more interesting however is the fact that a large excess of S02C12 (ca.20 equivalents) produces B&19 in 3040%yield. It appears likely that B9H9 or B9H9- C1 are first formed by oxidation of the corresponding anions and then these are chlorinated to give the observed B&19 because the BgC1g2- ion does not react with S0,Cl,.'07 Degradation of BloCllo and BllClll with chlorine produces B&19 in high yield; with hydrogen bromine and iodine mixed species B9C19-,X, are formed.'" Heterocyclic Boron Derivatives.-Oxidation of the complexes (22; R = Me or Ph) prepared from Co(C5H,BR) and [Fe(CO),(C,H,)], results in a novel ring contrac- tion producing Fe(C,H,R)(C,H,)' and boric acid.On attempted Friedel-Crafts acetylation of (22) a rather unique ring-member substitution occurs to give after hydrolysis Fe(C,H5Me)(CSH5)+ and RB(OH),; when carried out on Fe(C5H5BMe) the product was either Fe(C6HsMe)(C5H5BMe)' and/or Fe(C6H5Me) depending on the reaction conditions.109a (22) The addition of sodium cyanide to CO(C,H,BR)~ R = Me; Ph in acetonitrile results in the formation of the sodium borinates from which the first isolable Main Group borabenzene derivatives T1(C5H5BR) may be prepared by addition of thallium(1) The recently described metallo-p-diketone (22)reacts with all the boron trihalides at -35 "C to form metallo analogues of the well-known P-diketone complexes of BF,:'" Me Me /C -q F-9 (Co)4Re ,,H X=F+Jw (CO),Re ,BX, BX3 C-0 c-0 Me Me (22) N-Alkyl amino-acids react with BF3 to eliminate hydrogen fluoride and form cyclic (a-amino-carboxylato-N)boronderivatives" ' \ +BF R = CH2Ph; R' =Pr' Bu' Bus CH2COOH R = CH2CH =CHPh; R' =CH2Ph.lo' R. M. Kabbani and E. H. Wong J.C.S. Chem. Comm. 1978,462. 'OB S. B. Awad D. W. Prest and A. G. Massey J. Inorg. Nuclear Chem. 1978,40 395. '09 (a)G. E. Herberich and K. Carsten J. Orgunomerullic Chem. 1978,144 C1; (b)G. E. Herberich H. J. Becker and C. Engelke J. Organometallic Chem. 1978,153 265. C. M. Lukehart and L. T. Warfield Inorg. Chem. 1978,17,201. ''' J. Halstr~m,E. Nebelin and E. J. Pedersen J. Chem. Res. (S) 1978 80.F. A. Hart A. G. Massey P. G. Harrison and J. H. Holloway When diphenylborinic acid anhydride and N-methylacethydroxamic acid are mixed in absolute ethanol crystals of diphenylboron N-methylacethydroxamate (27) begin to precipitate after a few minutes; the 2,1,3,4-B02CN ring in (24) is essentially planar. Ph Ph Ph Ph \/ \/ B ?'-'p e) /C=N+ C-N \ /\ Me Me Me Me (244 (24b) Although it is difficult to give an exact formal description of (24) it may be best regarded as a 3 :1 hybrid of the resonance forms a and b.*12 A variety of BSiO-rings have been made from phenylboronic acid using reactions such as113 OH CISiMe 0-SiMe, / \ +Et3N Phi 'NMe + PhB\ /NMe -Et3NHC \ / OH CISiMez 0-SiMe? Me Me si%i,2 /OH C1-SiMe +Et,N PhB + 1 0 I CI-SiMe -Et3HNC1 PhB ,SiMe, \OH 0-SiMe Similar condensation reactions between phenylboronic acid and a,o-diols HO(CH2),0H n =5 6 10 or 12 give rise114a to equilibrium mixtures of oli-gomeric ringsfO-(CH2) -OB(Ph)Q.Tetrazadiborines are formed when 1,2-dimethylhydrazine is treated with either B (SMe)3 or B (NMe2) -XB Me Me N-N BX + MeNHNHMe 'BX X=SMe NMez \/ N-N Me Me The groups on boron may be substituted by a variety of reagents but these have to be chosen carefully to reduce the possibility of ring cleavage. For example although extensive cleavage occurs with boron tribromide bromine substitution can be effected by dimethylboron Both B and N organo-substituted tetra-zadiborines may be prepared directly by suitable choice of reactants114c 11* S.J. Rettig J. Trotter W. Kliegel and D. Nanninga Cunud. J. Chem. 1978 56 1676. U. Wannagat and G. Eisele 2.Nuturforsch. 1978 33b 475. 'I4 (a)U. W. Gerwarth Mukromol. Chem. 1978,179 1497; (b)H. Noth and W. Winterstein Chem. Ber. 1978 111 2469; (c) D. Nolle H. Noth and W. Winterstein Chem. Ber. 1978 111 2465. The Typical Elements -RB R' R' N-N RB(SMe)2 + R'NHNHRI /\ ,BR N-N R' R1 Reaction of 1,3,4,5-tetraethyl-2-methyl-l,3-diborolenewith cyclopenta-dienylnickel carbonyl dimer leads to the formation of the nickelocene analogue (25) From (25) it is possible to make triple-decker sandwich complexes in high yield using to so-called 'stacking' reaction technique Et Et n (25) + C5H5Co(CO) -(C,H,)NiEtBQBEtCo(C,H,i Me (26) Me Et Et n (25) + [C,H,Ni(CO)] -+ (C,H,)NiEtBOBEtNi(C,HS) v Me (27) The deep green air-stable complex (27) is paramagnetic (with 33 valence electrons); reduction gives the diamagnetic ion (27)- while treatment with silver tetrafluoro- borate produces the blue (27)'BF4- which is paramagnetic with two unpaired electrons being isoelectronic with (26)."' The di-iodothiadiborolene (28) has been prepared by first adding boron tri-iodide across hex-3-yne and then treating the cis-trans mixture of 3-diiodoboryl-4-iodo-3-hexene so formed with (IBS)3 Et Et Et Et c=c \ (IBS) \ EtCGCEt + BI -* /C=C / * RB ,BR S ',B \I (28; R = I) The two iodine atoms in (28)can be readily substituted by Me C1 Br OEt SMe and NMe2.'16 When (28; R=Me) is irradiated with either Cr(CO) or Mo(CO) in tetrahydrofuran complexes (28)M(C0)4 and (28),M(CO) are formed in which the thiadiborolene is thought to be acting as a penta-hapto ligand."' Like diborolene W.Siebert J. Edwin and M. Bochmann Angew. Chem. Infernal. Edn. 1978 17 868. W. Siebert R. Full J. Edwin and K. Kinberger Chem. Ber. 1978 111 823. 'I7 K. Kinberger and W. Siebert Chem. Ber. 1978 111 356. F. A. Hart A. G. Massey P. G. Harrison and J. H. Holloway thiadiborolene is also able to bond simultaneously to two metals so that triple- and even tetra- decker sandwich compounds can be built up:"' (28; R = Me)+ Mn2(CO)lo+ [C5H5Fe(CO)J2 -+ (C0)3Mn(28)FeC5H5 (C0)3Mn(28)FeC5H5 + C6H6+ A1CI3 + [C6H6Fe(28)Mn(C0)3]'AlC14-(CO)3Mn(28)Fe(28)Mn(CO) i heat In contrast the heterocyclic ring of benzodiazaboroles does not function as a ligand to the Cr(C0)3 moiety in (29),the bonding being exclusively via the benzo A novel rearrangement to yield benzoxazaboroles benzothiazaboroles and benzoselenazaboroles occurs when diborane reacts with benzoxazole or its sulphur and selenium ana10gues.l~~~ E = 0,S Se; (i) $B2H6;(ii) detected by n.m.r.Ring expansion by two atoms occurs when 1,3,2-diazaboracycloalkanesare treated with either phenyl isocyanate or phenyl isothiocyanate'20 e.g. Et Aniline bis (difluoroborondimethylglyoximato)nickel(II)forms as deep scarlet needles when aniline and Ni(dmgBF2)2 are mixed in warm dichloromethane. The dimeric nature of the planar parent Ni(dmgBF2)2 with a cis conformation of the BF2 groups is retained upon reaction with aniline.The nickel atoms are each surrounded by four nitrogen atoms ofthe closely planar macrocycle and an aniline is co-ordinated in an axial position to form an irregular square pyramid. The two formula units of the dimer (Ni-Ni = 3.654A) are non-equivalent the Ni-N(ani1ine) distances 2.724 'I8 W. Siebert C. Bohle C. Kriiger and Y.-H. Tsay Angew. Chem. Infernut.Edn. 1978,17 527. 'I9 (a)R.Gotze and H. Noth J. Orgunomefulfic Chem. 1978,145,151; (b)K. K. Knapp P. C. Keller and J. V. Rund J.C.S. Chem. Comm. 1978,971. 12') U. W. Gerwarth and K. D. Muller J. Organomerullic Chem. 1978 145 1. The Typical Elements and 2.602 A differ significantly and the two nickel atoms are displaced unequally out of the equatorial co-ordination plane by 0.1 18 and 0.138 A.121 The seven-membered borepin ring of spiro(!?H-borepino[2,3-6:7,6-b']dithio-phene-9,2'-[ 1,3,2]oxazaborolidine} (30) is in a boat configuration; the five- membered oxazaborolidine ring in a half chain conformation is practically at right angles to the borepin ring giving the boron atom essentially tetrahedral co-ordination.Neither thiophene ring shows a significant deviation from planarity.'" The vibrational spectrum of B-trimethylborazine has been recorded from 200 to 4000cm-' and assignment of fundamentals proposed with the help of a study of selected isotopically labelled species. Although extensive mixing of vibrations was observed it is evident that methylation of the borazine ring has virtually no influence on the electronic nature of the heter~cycle.'~~ Reaction of the bifunctional 2,4- dichloro-1,3,5,6-tetramethylborazinewith a mixture of dimethylformamide and dimethylamine leads to low yields of a macrocyclic polyborazine in which six borazine rings are linked by oxygen bridges.lZ4 Boron-nitrogen Compounds.-The layer form of boron nitride reacts with S206F2to form'25 a deep blue electrically conducting solid of approximate composition (BN)4+S03F-.A close study has been made of the thermal decomposition of ammonia-borane; a vigorous decomposition with rapid hydrogen formation begins at 120 "C and is followed by a slower gas evolution between 145 and 200 "C. The composition of the white residue is approximately BNH2.' after heating to 170 "C and BNH0.8-l.2 after heating to 200 "C.The infrared spectrum of a sample pyrolysed for a short period at 500-600 "C resembled that of boron nitride although an NH band at 3450 cm-' was still present.1260 When ammonia is passed through molten ammonia-borane at 125 "C diaminoborane (NH2)2BH is formed in 10-17% yield. In the liquid state diaminoborane decomposes to a glassy solid but it is stable in liquid ammonia and may be kept in the gas phase at room temperature for several days. The short B-N bonds 1.42 A suggest substantial 7r-bond character in the NBN framework.'26b 121 R. S. Vagg and E. C. Watton Actu Cryst. 1978 B34 2715. 122 I. Cynkier and H. Hope Actu Cryst. 1978 B34 2990.123 K. E.Blick E. B. Bradlry K. Niedenzu M. Takasuka T. Totani and H. Watanabe 2.anorg. Chem. 1978,442 183. 124 A.Meller and H.-J. Fiiilgrabe Chem. Ber. 1978,111,819. 125 N. Bartlett R. N. Biagioni B. W. McQuillan A. S. Robertson and A. C. Thompson J.C.S. Chem. Comm. 1978,200. 126 (a)M. G. Hu R. A. Geanangel and W. W. Wendlandt Thermochim. Actu 1978 23 249; (b) T. S. Briggs W. D. Gwinn W. L. Jolly and L. R. Thorne J. Amer. Chem. SOC.,1978,100,7762. F. A. Hart A. G. Massey P. G. Harrison and J. H. Holloway A microwave structural investigation of the weak adduct tri-methylamine-trimethylboraneshows that the B-N bond (1.698k0.01A) is the longest of any BX3 adduct with trimethylamine; the B-C bond length of 1.69k 0.04 8 also appears to be the longest yet reported.Steric effects are considered to be responsible at least in part for the decrease in stability of the trimethylborane adduct relative to that of boron triflu~ride.~" An apparently general synthesis of amine-cyanoboranes involves refluxing sodium cyanotrihydroborate with the corresponding amine hydrochlorides in tetra- hydrofuran.128 Ammonia-cyanoborane can be prepared by the amine replacement reaction C6HSNHZBH2CN+NH3 + H3NBH2CN+C6HSNH? The B-N and B-C bond lengths in this adduct are 1.577 and 1.589A respec-tive~~.*'~ Aminoboranes which show no evidence of decomposition when heated at 150-200 "C in an inert atmosphere have been made via the reaction NR2 NR2 / +2NH3 / (Me3Si)'N-B ____* (Me3Si)'N-B R = Me Et Pr' -NH4CI \ \C NH2 The bis(trimethylsily1)amino group is twisted about 90" out of the plane defined by the boron and three nitrogen atoms.Hence the boron is sterically protected from nucleophilic attack which presumably explains the unusual thermal stability of these compounds since the necessary intermolecular interaction is prevented.I3' The bis(di-isopropy1amino)amino boranes (Pr2'N)2BNRR' possess helically chiral configurations which are stereochemically rigid at low temperatures. N.m.r. line shape analysis indicates that these molecules enantiomerize by correlated BN rotations through transition states in which the substituents attached to two of the nitrogen atoms are in the plane of the BN3 unit while those on the third nitrogen are perpendicular to this plane.131a Phosphorus atoms act as the donor sites in complexes such as (CO)SMR2PB(NR')2 [(CO)SM]2(PEt2)2BNEt2 cis-M(C0)4(PR2)2BNR and c~~-M(CO)~(PR~)~B~(NM~~)~ where M is chromium molybdenum or tungsten.13' N.m.r. studies of scrambling reactions between B(NEt,),/PCl and B(NEt&/XPC13 X =0 S show that the mixed species are more favoured than would have been the case if a completely random mechanism was involved. In the B(NEt,),/PCl system the chlorine substituent displayed a preferential affinity for phosphorus over boron while the reverse was true in the systems involving four-co- ordinated phosphorus. It was assumed that for the former system the more effective P. M. Kuznesof and R. L. Kuczkowski Znorg. Chem. 1978 17 2308.'** P. Wisian-Neilson M. K. Das and B. F. Spielvogel Inorg. Chem. 1978 17 2327. A. T. McPhail K. D. Onan B. F. Spielvogel and P. Wisian-Neilson J. Chem. Res. (S),1978 205. 130 D. M. Graham J. R. Bowser C. G. Moreland R. H. Neilson and R. L. Wells Znorg. Chem. 1978,17 2028. 13' (a)K. K. Curry and J. W. Gilje J. Amer. Chem. Soc. 1978 100 1442; (b)H. Noth and S. N. Sze Z. Nuturforsch. 1978 33b 1313. The Typical Elements rr-donor ligand NEt, would be bonded to the better acceptor B; in four-co- ordinated phosphorus system the presence of oxygen and sulphur on the phosphorus centre could enhance its effective electronegativity thus perhaps increasing its acceptor ability to such a degree that it became superior to boron in this N-Substituted trimethylsilylamides react with 2-chloro-1,3-dimethyl-l,3,2-diazaborolidine chloro(dimethylamino)phenylborane tris(diethy1amino)borane and B-chloropentamethylborazine to give monomeric amido boranes and borazines in nearly quantitative yields:'33 H2 H2 c-c II 0 R2 Me MeN ,NMe R'=Me R2 =Me R'-C-N / B R' = Ph R2= Me II + c,By-iH2-\ \ I RI R' =Me R2= Ph SiMe N-cH R2/N\ C/ Me II 0 0 The phosphiniminoboranes prepared via the reaction Ph3P=NSiMe3 + R2BX + Ph3P=NBR2 R = F C1 Br Bun Ph X = F C1 Br are monomeric in the gas phase; in solution the dihalogeno compounds are asso- ciated probably having a dimeric Reactions of methyl bis(methy1thio)borane with various hydrazines have been described; 1,1-dimethylhydrazine gives the hydrazinoboranes MeB(SMe)NHNMe2 and MeB(NHNMe2)2.Symmetrical dimethylhydrazine reacts rapidly to produce the bis(bory1hydrazino)methylborane(31) or hexamethyltetrazadiborine (32) depend-ing on the reaction ratios Me BSMe Me / Me Me N-N / N-N / Me \ MeNHNHMe + MeB(SMeI2 -* MeB \ MeB BMe ,Me \I N-N N-N Me \ Me Me BSMe Me (32) 13* J.-P. Costes G. Crcs and J.-P. Laurent J. Inorg. Nuclear Chem. 1978 40 829. 133 W. Maringgele and A. Meller Chem. Ber. 1978,111,538; A. Meller W. Maringgele and K.-D. Kablau Z. anorg. Chem. 1978,445 122. 134 W. Maringgele A. Meller H. Noth and R. Schroen 2.Naturforsch. 1978 33b 673. 198 F. A. Hart A. G. Massey P. G. Harrison and J. H. Holloway Only the five-membered triazadiborolidine ring derivative (33) could be isolated with m~nomethylhydrazine'~~ Me H N-N MeB BMe N' I /N\ H Me The reactive N-H bonds in Me,BNHNMe and Me2BNHSiMe3 can be metallated by methyl-lithium the intermediate salt [Me,BNHR]Li being detectable by n.m.r.136 Berates.-Boron atoms lie at the centres of equilateral triangles of oxygens in the isolated BO groups of NdGa3(B03)4 and the gallium atoms are octahedrally co-ordinated by oxygen.137 In synthetic manganese kurchatovite CaMn(B205) two triangular B03 units are linked through a common oxygen atom to form the B20s4- groups.138 The polymeric repeating B305 unit in LiB,O6 has two planar three-co- ordinated and one tetrahedral four-co-ordinated boron atoms; the compound is made by reaction of LizO with water-free boric A redetermination of the structure of borax by single crystal neutron diffraction fully confirms the conclusions of an earlier X-ray study and also provides accurate locations of the hydrogen atoms; each stoicheiometric anion B4072- incorporates two water molecules to form the B405(OH)42- gro~ping.'~' The synthetic borate Na2[B406(OH)2] has B-0 chains with the repeat unit B406(OH)22- in which there are two triangles and two tetrahedra condensed in a double ring arrangement.Sodium atoms are linked to oxygen atoms from three different chains so that a three-dimensional structure further strengthened by hydrogen-bonding is formed. 14' An isolated polyanion B506(OH),- is present in NaB506(0H)4 and is formed by one tetrahedron and four triangles in the shape of a double hexagonal ring; the two rings are almost perpendicular to each other (34).14 H 0 \ /OH /B-o\...O-B 0 B. /o \ '0-B, B-0 OH 0' H 135 D. Nolie and H. Noth Chem. Ber. 1978 111,469. 136 H.Fusstetter and H. Noth Chem. Ber. 1978 111 3596. 137 E.L. Belokoneva L. I. Al'shinskaya M. A. Simonov N. I. Leonyuk T. I. Timchenko and N. V. Belov Zhur. strukt. Khim. 1978,19,382. 13' 0.V. Yakibovich M. A. Simonov and N. V. Belov Doklady Akad. Nauk S.S.S.R.,1978 238 98. 139 H. Konig and R. Hoppe 2.anorg. Chem. 1978,439 71. H. A. Levy and G. C. Lisensky Acta Cryst. 1978 B34 3502. 141 S. Menchetti and C. Sabelli Acta Cryst. 1978 B34 1080. 142 S. Menchetti and C. Sabelli Acta Crysf. 1978 B34 45. The Typical Elements 199 Several quaternary ammonium salts -of the B506(OH),- anion have also been described.143 A refinement of the structure of the industrial bleaching agent disodium tetra- hydroxo-di-p-peroxo-diboratehexahydrate Na2[B2(02)2(OH)4],6H20 confirms the original work. The compound contains centrosymmetric cyclic B2(02)2(OH)42- ions in which the boron atoms are joined by two peroxo bridges and their tetrahedral co-ordination is completed by terminal OH groups. 144 Selected Organometallic Topics.-The barrier to internal rotation in phenylboron dichloride is 13.6f0.8 kJ mol-I as deduced from the microwave spectrum; this is in line with the value for phenylboron difluoride and considerably less than the previous estimate of 188 kJ mol-' calculated from infrared data.',' Diphenylborane made in situ by either the reaction of methoxydiphenylborane with LiAlH or addition of boron trifluoride etherate to Ph2BH,pyridine reacts readily with olefins to give high yields of alkyldiphenylboranes; the latter method of generation is suitable for the hydroboration of olefins containing functional groups sensitive to lithium tetrahydroaluminate.The synthesised alkyldiphenylboranes react with methylvinylketone to give good yields of the corresponding 4-alkyl-2- butanones whereas only one alkyl group of a trialkylborane can be transferred 146 Ill RBR +:c=c-c=o + H2° + R-C-C-C=O+R:BOH I I Ill R' = Ph or alkyl The spectral changes that occur on solidification of tris(perfluoroviny1)borane indicate the presence of two conformers in the gas and liquid phases neither of which is planar as might have been expected from the structure of trivinylborane.Even though the fluorine atoms on adjacent C2F3 groups are separated by more than twice their van der Waals radii the twist about the B-C bonds must relieve unfavoured steric and/or electronic interactions. The 'twisted' C3conformation is a geometry which severely limits the amount of p,,-p, overlap that is possible in this molecule. It is concluded that there is little iit any multiple bond character in the B-C bonds.',' Similarly there is apparently little interaction between the diene .rr-system and the electron deficient boron in 1-methyl- 1,4-dihydroborabenzene. 14* Bis-cyclopentadienylmercury reacts with dimethylboron chloride at -78 "C to form 5-C,H,BMe2 which is fluxional down to -90 "C;above -15 "C a 1,5 hydrogen shift occurs to give a mixture of the two 'vinyl' isomers (C,H,),Hg + Me,BCI -78"c_ above BMe 143 G.Heller and B. Bichowski 2.Nuturforsch. 1978 33b 20. 144 M. A. A. de C. T. Carronodo and A. C. Skapski Actu Cryst. 1978 B34,3551. 145 W. Caminate and D. G. Lister J.C.S. Furaduy 11,1978 896. 146 P. Jacob J. Organometallic Chem. 1978,156 101. 141 J. D. Odom E. J. Stampf J. R. Durig V. F. Kalasinksy and S. Riethmiller J. Phys. Chem. 1978 82 308. 14' S. A. Sullivan H. Sandford J. L. Beauchamp and A. J. Ashe J. Amer. Chem. SOC.,1978 100 3737. F. A. Hart A. G.Massey P. G. Harrison and J. H. Holloway Pentamethylcyclopentadienyldimethylboranecannot undergo a hydrogen shift and consequently is stable as the 5-isomer at room temperature whilst remaining fluxional down to -90 0C.149 Me Me,C,Li + Me,BCI -+ Me@&BMe2 Me a-Methoxyvinyllithium adds to trialkylboranes forming the Li'[R3BC(OMe)=CH2]-salts which are stable at -80 "C; on warming to room temperature however an alkyl group migration occurs to give Li'[R2B(OMe)CR=CH2]-.150 High yields of substituted allenes have been obtained by reacting alkynyltrimethylstannanes with trialkylboranes:151 RiB\ ,SnMe R:B + Me,SnCrCR' 4 [R.;B--CGCR2Sn'Me,] -C=C R' /\ R2 Reagents i THF or hexane at 0 "C; ii Me3SnC=CR3 at 80-120 "C 2 Aluminium Oxygen plays a dual role in the corrosion of aluminium in oxygen-saturated water.It takes part in the oxygen reduction reaction so providing the cathodic part of a corrosion cell and it will also repair the passivating surface oxide film. The repair may be impeded by the presence of anions in solution thus nitrite iodide bromide and chloride increasingly impede the repair reaction whereas sulphate and nitrate have no influence at all. Chloride ion is known to adsorb onto the surface; following adsorption a thermodynamic equilibrium is set up between the surface oxide and aluminium chloride and depending on the state of this equilibrium the surface will remain passive or will undergo pitting corrosion. Below a critical surface chloride concentration the corrosion may repa~sivate.~~~ The infrared stretching frequencies of the diatomic molecules AlH and AID isolated in an argon matrix at 14 K are 1593 and 1159 cm-' re~pectively.'~~ A study of the decomposition of aluminium sulphate has shown that the 'anhy- drous' salt made by usually accepted methods contains about 0.03 mol of water per mol of sulphate ion.The solid product when the decomposition is carried out at 149 H. D. Johnson T. W. Hartford and C. W. Spangler J.C.S. Chem. Comm. 1978 242. A. B. Levy S. J. Schwartz N. Wilson and B. Christie J. Organometallic Chem. 1978 156,123. ''' B. Wrackmeyer and R. Zentgraf J.C.S. Chem. Comm. 1978,402. "* R. T. Lowson Austral. J. Chem. 1978,31 943. 153 R.B. Wright J. K. Bates and D. M. Gruen Znorg. Chem. 1978 17 2275. The Typical Elements 201 600 "C is an amorphous form of aluminium oxide which has a very high surface area ca.165 m2 g-'.15 There has been considerable activity this year in the field of aluminium chloride and chloroaluminate melt chemistry. Silica glass is attacked by anhydrous alu- minium chloride at temperatures above 300 "C to produce silicon tetrachloride; the solid product is either AlOCl or A1203depending on the temperature. When a mixture of aluminium and aluminium chloride is heated to approximately 350 "C in a silica tube silica 'foil' is deposited on the walls and is assumed to arise from reduction of silicon tetrachloride-formed initially by attack of the tube-by gaseous A12Cl A single-crystal Raman and infrared spectral study has been carried out on A1Cl3,6H2O; v1 for A106 is placed at 524 ~rn-'.'~~ The highly hygroscopic potassium tetrachloroaluminate contains discrete but slightly distorted AlC1,- anions in which the Al-Cl distances vary from 2.119.to 2.140 A.157 Ammonium tetrachloroaluminate which is isostructural with ammonium perchlorate has similar Al-Cl bond lengths to those of the alkali tetrachloroaluminates (average 2.117 Although solid acetyl chloride-alu- minium chloride is ionic with AlCl,- ions a 27Aln.m.r. study shows that the complex has a donor-acceptor structure in dichloromethane The infrared spec- trum of the tetrachloroaluminate anion in chloroaluminate melts has been recorded for the first time.'60 Fused chloroaluminate melts of composition (Na,K)Al,Cl are essentially ionic M+A12C17-. The amount of free aluminium chloride is small and the equilibrium 2AIC14-+Al2Cl6 S 2A12C17-is reached rapidly.16' Similarly the Raman spectra of molten aluminium chloride/ 1-butylpyridinium chloride mixtures varying in molar composition from 0.75 :1.O to 2.0 :1.O indicate the presence of AlC1,- and A12C17- ions. The equilibrium constant for the above reaction was found to be significantly larger than that for alkali metal chloride-aluminium chloride melts. Aluminium chloride/alkylpyridinium chloride mixtures have relatively low liquidus temperatures and thus make useful aprotic molten salt media of varying acidity for studying the reactions of many organic or thermally unstable compounds. 162 A mass spectrometric investigation of the system CuC1(s)/Al2Cl6(g) established that Cu3A1Cl6 and Cu2A12C18 are the principal gas complexes.The complexes are assumed to have cubic-type structures similar to that of CU,C~,'~~ e.g. (35). The cyclic structure (36) for the gaseous complex CuA12C18 formed when CuCl and A12C16 are heated together at 250-300°C in a sealed tube has been 154 G. F. Knutsen and A. W. Searcy J. Electrochem. SOC. 1978 125 327. 155 H.Schafer 2.anorg. Chem. 1978 445 129. D. M. Adam and D. J. Hills J.C.S. Dalton 1978 782. 157 G. Mairesse P. Barbier and J.-P.Wignacourt Acra Crysr. 1978 B34 1328. G. Mairesse P. Barbier J.-P. Wignacourt A. Rubbens and F. Wallart Canad. J. Chem. 1978,56,764. 159 J. Wilinski and R. J. Kurland J. Amer. Chem. SOC., 1978 100 2233. I6O N.R. Smyrl G. Mamantov and L. E. McCurry J.Znorg. Nuclear Chem. 1978,40 1489. 161U. Anders and J. A. Plambeck J. Inorg. Nuclear Chem. 1978,40 387. 162 R. J. Gale B. Gilbert and R. A. Osteryoung Znorg. Chem. 1978 17 2728. 163 H. Schafer and H. Rabeneck 2.anorg. Chem. 1978 443 28. 16* C. W. Schlapfer and C. Rohrbasser Inorg. Chem. 1978 17 1623. F. A. Hart A. G. Massey P. G. Harrison and J. H. Holloway ~ha1lenged.l~' At higher temperatures CUA12Cls loses aluminium chloride to form CuAlCl which probably has the structure (37).165 A DZhstructure having palladium as the central atom is suggested for the gaseous complex PdA12Cls formed in the heated AlzC16/PdClz Two complexes EuAl3Cll1 and EuAl,Cl,, are thought to exist in the vapour above liquid mixtures of aluminium chloride and europium(I1) chloride.It is calculated that the concen- tration of Eu" which can be maintained in the gas phase at 700 "C is increased by a factor of 10'2.5by the presence of the aluminium trichloride.'66 From a study of the Raman spectrum of elemental sulphur dissolved in either molten aluminium tri- chloride or chloroaluminate melts it is concluded that the sulphur dissolves as Ss.'67 Melts of sodium chloride and methylaluminium dichloride have been shown to have a high specific conductivity 0.19 ohm-' cm-' at 180"C. Electrolysis of these melts using sacrificial anodes such as tin and mercury leads to fair yields of the metal methyls.168 Dibromo- and di-iodo-dimethylaminoaluminiumhave been prepared by the action of the corresponding mercury(I1) halide on dimethylaminoalane H2AINMe2+HgX2 + Hg +Hz+X2AlNMe2 The molecules exist as dimers with a planar four-membered ring of alternating aluminium and nitrogen atoms.169 Aluminium tri-iodide reacts with iodine azide in benzene yielding di-iodoaluminium azide I,AlN,; treatment of this with liquid bromine gives BrzA1N3.170 The mixed complexes LiMg(AlH4)3 and LiMg3(AlH4)7 together with Mg(AIH,)z,EtzO have been prepared from magnesium chloride and lithium tetra- hydroaluminate in ether s01ution.l~' t-Butylalcoholysis of MAlH at room temperature for M=Li Na or K and at 135 "C for M=Cs produces the tris(t- butoxy)aluminates M[HAl(OBu'),] the anion HAI(OBU')~- being tetrameric.The stability towards further alcoholysis increases from Li to Cs.17' Reaction of the alkaline earth metals with tris(isopropoxy)aluminium in boiling isopropanol in the presence of HgC12 as a catalyst gives the double alkoxides {M[A1(OPri)4]2}n where n is 1 for M=Mg and n is 2 for M=Ca Sr or Ba.165 G. N. Papatheodorou and M. A. Capote J. Chem. Phys. 1978,69 2067. 166 M. Sorlie and H. A. Oye J. Znorg. Nuclear Chem. 1978,40,493. 167 R. Huglen F. W. Poulsen G. Mamantov R. Marassi and G. M. Begun Znorg. Nuclear Chem. Letters 1978 14 167. A. von Rumohr and W. Sundermeyer Z. anorg. Chem. 1978,443 37. 169 A. Ahmed W. Schwarz and H. Hess 2.Naturforsch. 1978 33b 43. 170 K. Dehnicke and N. Kriiger Z. anorg. Chem. 1978,444 71. ''I B. M. Bulychev K. N. Semenenko and K. B. Bitsoev Koord. Khim. 1978,4,374. 17* M. I. Karpovskaya N. Ya. Turova G.A. Kirakosyan V. P. Tarasov and N. I. Kozlova Koord. Khim. 1978 4 907. The Typical Elements 203 Treatment of the double alkoxides with an excess of either t-butylalcohol or t-amylalcohol in boiling benzene leads to partial alcoholysis of isopropoxy groups and the formation of either M[A1(OPri)(OR),I2 (M=Mg Ca Sr) or Ba[Al(OPri)2(0R)2]2 which are volatile and monomeric.173 The volatile double isopropoxide of tin and aluminium S~[AI(OPT~)~]~ made by treating Na[Al(OPr'),] with tin tetrachloride is monomeric in boiling benzene. 174 Three main bands corresponding to orbital binding energies of approximately 10 13.5 and 27 eV occur in the X-ray photoelectron spectrum of spinel MgA1204. The two bands of lowest energy are mostly oxygen 2p in character whilst the band at 27 eV is almost exclusively oxygen 2s.Aluminium 3s and 3p character are found in both of the least tightly bound orbitals but somewhat more is present in the 13.5 eV band than that at 10 eV; this feature is reversed for the magnesium 3p orbitals and reflects the different bonding situation of the aluminium and magnesium atoms in the spinel Pentacalcium trialuminate 5Ca0,3A1203 better known to cement chemists as unstable C5A3 has a structure which consists of alternating twisted sheets of distorted AlO tetrahedra and layers of calcium atoms which lie approximately perpendicular to the [OOl] plane; the A104 tetrahedra are linked through corners to form a network of five-membered rings.176 Previous doubts concerning the degree of hydration of crystalline potassium trioxalatoaluminate have been dispelled.The structure is comprised of discrete trioxalatoaluminate anions potassium cations and three water molecules per formula unit. 177 The hygroscopic crystals of A1(H2PO4), produced by evaporation of viscous solutions of aluminium in concentrated phosphoric acid possess a structure made up of isolated AlO octahedra stacked with corner-sharing 02P(OH) tetrahedra to form columns i[Al(H2P04)3] parallel to the crystal c axis. The columns are linked together by hydrogen-bonds each OH group acting simul- taneously as a proton donor and a~cept0r.l~~ The crystal structure of aluminium dihydrogenphosphate-monohydrogenphosphate-monohydrate(acid aluminium phosphate) contains macromolecular units ~[A1(HzP04)(HP04)(H20)],, consisting of A105(H20) octahedra which share vertices with PO,(OH) and P03(OH) tetra- hedra; neighbouring layers are held together by hydrogen In the basic sulphate AlZ(OH),SO4,7H2O (aluminite) an important structural feature is the presence of the complex ion [A~,(OH)~(HZ~)~]~' consisting of four edge-sharing A106 octahedra; these ions are connected to each other to make chains running in the a direction and are linked by hydrogen-bonds to SO tetrahedra.In the asymmetric unit there are seven water molecules four of which lie among the chains and tetrahedra as free water and three are co-ordinated together with OH to the aluminium atoms as ligand water. Hence the crystal chemical formula is best written i.e.[A12(OH)4(H20)3]S04,4H20a hydrated sulphate of a hydroxoaluminium complex.I8O 173 R.C. Mehrotra S. Goel A. B. Goel R. B. King and K. C. Nainan Znorg. Chim. Acta 1978,29 131. R.C. Mehrotra A. K. Rai andN. C. Jain J. Znorg. Nuclear Chem. 1978,40 349. 17' D. E. Haycock C. J. Nicholls D. S. Urch M. J. Webber and G. Wiech J.C.S.Dalton 1978 1785. 176 M. G. Vincent and J. W. Jeffery Acta Cryst. 1978 B34 1422. 177 D. Taylor Austral. J. Chem. 1978 31 1455. 178 R. Kniep and M. Steffen Angew. Chem. Internat. Edn. 1978 17 272. 179 R. Kniep D. Mootz and A. Wilrns 2. Naturforsch. 1978 33b 1047. C. Sabelli and R.T. Ferroni Acru Cryst. 1978 B34 2407. 204 F. A. Hart A. G.Massey P. G.Harrison and J. H. Holloway Two reports describe the synthesis of compounds containing the first known Al-Ge bonds.Tris(trimethylgermy1)aluminium has been isolated as a tetrahydro- furan complex from the reaction THF Hg[GeMe3I2+2A1 -A1[GeMe3l3,THF5MeA1[GeMe3I2 pentane It is said to have 'astonishing thermal stability' although being spontaneously inflammable in air. Lithium triorganogermyltrihydroaluminates,which are stable under an inert atmosphere are intermediates in the LiA1H4-reduction of hexa- organodigermanes. 182 3 Gallium Using a diamond anvil cell the crystal structures of the high pressure Ga" and Ga"' forms of gallium have been studied. Gal' has a body-centred cubic structure with twelve atoms in the centred cell and each atom having eight nearest neighbours at 2.78 A (2.6 GPa 313 K); Ga'" has a body-centred tetragonal cell with two atoms in the cell each atom having four nearest neighbours at 2.81 8 and eight second neighbours at 2.99 A (2.8 GPa 298 K).lg3 Gallium trichloride and tribromide form 1:1 molecular complexes with a variety of pyridine-N-~xides."~ The 1 1 trimethylphosphine and trimethylarsine adducts of gallium trichloride adopt eclipsed rather than the expected staggered con-formations in the solid state.The 35Cl NQR frequencies of PMe3GaC13 and PEt3GaC13 are among the lowest known for gallium trichloride adducts indicating that phosphines are extremely good donors towards GaC13. lS5 The absolute infrared spectral intensities of v3 and v, and the Raman intensity of v1 (relative to vl of CCl,) have been measured for the tetrahedral MX,-anions M = Ga In or T1.lS6 Tetra- methylstibonium tetrachlorogallate possess a structure containing isolated slightly distorted cationic and anionic tetrahedra with averaged Sb-C and Ga-Cl bond lengths of 2.126 and 2.172 A re~pectively."~The stoicheiometric reaction between gallium metal and gallium trichloride tribromide or tri-iodide in benzene at 60 "C provides a facile synthesis for the lower halides Ga,X,.An excess of gallium with the tri-iodide produces Ga416 which is formulated as (Ga+)2Ga2162-; the bromide Ga&6 cannot be made by this method as it decomposes to Ga2Br4 and Ga in benzene.lS8 67 Ga is used clinically as a tumour scanning agent but it has been found that inorganic phosphate inhibits gallium uptake by L1210 leukemic cells.A 71Ga and 31 P n.m.r. study has shown the gallium-phosphoric acid system to be complicated; as many as four distinct species are present of which two were identified as GaH3POd3+ in1 L. Rosch and W. Erb Angew. Chem. Znternat. Edn. 1978,17 604. 182 N.Duffant J. Dunogues R. Calas J. Gervol P. Riviere J. Satge and A. Cazes J. Organomefallic Chem. 1978,149,57. 183 L.Bosio J. Chem. Phys. 1978,68 1221. 184 J. R. Masaguer A. Sanchez J. S. Casas J. Sordo and A. Castineiras J. Znorg. Nuclear Chem. 1978,40 355; A. Sanchez J. S. Casas J. Sordo and J. R. Masaguer J. Znorg. Nuclear Chem. 1978,40,357. 185 J. C. Carter G. Jugie R. Enjalbert and J. Galy Znorg. Chem. 1978 17 1248. I86 S.P.Andrews P. E. R. Badger P. L. Goggin N. W. Hurst and A. J. M.Rattray J. Chem. Rex (S),1978 94. 187 H.-D. Hausen H. Binder and W. Schwarz 2.Naturforsch. 1978,33b 567. 188 J. C. Beamish M. Wilkinson and I. J. Worrall Znorg. Chem. 1978 17 2026. The Typical Elements and GaH2P0,2' complexes the others being assumed to be gallium-phosphoric acid polymers. 189 The two terdentate anionic ligands (38)190 and (39)191 form octahedral M(ligand) complexes with Mn Fe Co Ni Cu and Zn; the Ni(38) complex exists in mer and fac forms the gallium atoms in both isomers having distorted tetrahedral co-or- dination with OGaN angles of 90.3-93.2" and CGaC angles of 122.0-123.3°.'90 A number of organometallic compounds have been made using (39) uiz. (39)-Mn(C0)3 (39)Mo(CO),NO (39)Mo(CO),7 3-C4H7 and (39)Mo(C0),7 3-C3H5 ; a structure determination on the latter confirmed the tridentate nature of the gallium ligand.'" 'CH JH (38) Lithium gallate of stoicheiometry LiGa02,6H20 is correctly formulated as [Li(H20),]'[Ga02,2H20]- and not as containing the tetrahydroxogallate anion.The GaO tetrahedron is very distorted the OGaO angles varying from 71" to 127.7°.'92 The selenogallate T1' GaSe crystallizes with a layer structure. The main features of the layers are large corner-linked Ga4Selo tetrahedra which themselves are formed from four corner-linked GaSe4 tetrahedra. The thallium atoms are situated on straight lines parallel to the edges of the Ga4Se, groups and are surrounded by six selenium atoms in the form of a trigonal prism.193 4 Indium The vapour pressure of indium measured over the temperature range 1165 -1344 K via the rate of weight loss of zirconia Knudsen cells can be represented by log p = -~lY9O6 +5.08(f0.02) atmospheres.T This gives the enthalpy of vaporization at 298 K as 57.3 f0.3 Kcal mol-' which is slightly lower than earlier ~a1ues.l~~ In indium trifluoride trihydrate the indium atoms are octahedrally co-ordinated by four fluorines and two oxygens. Adjacent octahedra share their apical fluorine atoms to form infinite chains parallel to the c axis whilst in the equatorial plane there are two fluorine atoms and two water molecules distributed in disorder around the indium; the third water molecule is lattice water.195 Two types of indium occur in lS9 R. E. Lenkinski C. H. F. Chang and J.D. Glickson J. Amer. Chem. Soc. 1978 100 5383. 190 K. S. Chong S. J. Rettig A. Storr and J. Trotter Canad. J. Chem. 1978 56 1212. 19' K. R. Breakell S. J. Rettig D. L. Singbeil A. Storr and J. Trotter Canad. J. Chem. 1978 56 2099. 192 C. Caranoni G. Pepe and L. Capella Acta Cryst. 1978 B34 741. 193 D. Miiller and H. Hahn 2.anorg. Chem. 1978 438 258. 194 J. Valderram-N and K. T. Jacob J. Inorg. Nuclear Chem. 1978,40,993. 195 P. Bukovec and V. Kaucic Znorg. Nuclear Chem. Letters 1978 14 79. 206 F. A. Hart A. G.Massey P. G.Harrison and J. H. Holloway crystalline Rb21n3Fll ;two indium atoms per 'In3F11' unit have regular pentagonal bipyramidal co-ordination with In-F distances in the range 2.10-2.13 A the other indium having very deformed octahedral co-ordination.Parallel sheets formed by edge- and corner-sharing pentagonal bipyramids are joined together by infinite and parallel chains of corner-sharing octahedra. The large tunnels in the three- dimensional net-work thus produced hold the rubidium ions. 196 The electrolytic behaviour of potassium chloride in water-dimethyl sulphoxide is practically identical with its behaviour in water up to 50% by weight of DMSO. Thus Walden's rule is followed very closely implying that the only effect on the speeds of the ions is that of viscosity. The behaviour of indium trichloride is very different. The conductance increases rapidly with dilution in the dilute range and is time depen- dent. It appears probable that the ionization of indium trichloride takes place in steps and that in dilute solutions progressive hydrolysis takes place the hydrolysis products precipitating out of solution.19' Solid magnesium calcium and manganese dichlorides react with gaseous indium trichloride above 500 "C to form MIn,Cl,(g) and MInC15(g) the former being the dominant species between 500 and 530 "C; with copper(I1) chloride however only CuInCl,(g) could be dete~ted.'~~.'~~ It is concluded from a study of their photoelectron spectra that gaseous InCl and TlCl monomers are covalent molecules in which both the ns and the np electrons are involved in bonding; thus it would be incorrect to conceive of the metal s electrons as being inert non-bonding pairs. The spectra also confirmed the view that the inner d shells of indium and thallium should be regarded as part of their atomic cores.'99 Indium has slightly deformed octahedral co-ordinations in both NH41n(S04)2,- 4H2O2O0 and NH41n(Se04)2,4H20.201 Two vertices of both the SO or Se0 tetrahedra are shared and the remaining octahedral positions are completed by two trans water molecules.The low temperature form of In2Se3 has two types of indium present one with trigonal bipyramidal and the other with tetrahedral co-ordination.202 A second form of In2TeS has been isolated from the reaction of stoicheiometric amounts of tellurium and indium at 550 "C. The material is composed of separate planar sheets of atoms stacked perpendicular to the c axis; the sheets which are about 7 8,thick consist of chains of four-membered In2Te2 rings in which each indium is tetrahedrally co- ordinated average In-Te distance 2.8498,.The rings alternate with and are cross-linked by groups of three tellurium atoms which on an ionic formulation are Te32-polyanions. These polyanions are linked by bonds of intermediate strength to form continuous chains of tellurium atoms running across the ~heets."~ In view of the strong phosphorus-sulphur bonding in InPS4 (average P-S bond length 2.043 A) it is suggested that the compound be classified as a thiophosphate. J.-C. Champarnaud-Mesjard and B. Frit Acta Cryst. 1978 B34 736. A. N. Campbell Canad. J. Chem. 1978 56 355. F. Dienstbach and F. Emmenegger J. Inorg. Nuclear Chem. 1978,40 1299. 199 R. G. Egdell and A. F. Orchard J.C.S. Faraday 11 1978 1179.N. N. Mukhtarova R. K. Rastsvetaeva and V. V. Ilyukhin Doklady Akad. Nauk S.S.S.R. 1978,239 322. '01 E. N. Soldatov E. A. Kuzinin and N. V. Kadoshnikova Doklady Akad. NaukS.S.S.R. 1978,240,362. 'O' A. Likforman D. CarrC and R. Hillel Acta Cryst. 1978 B34 1. '03 P. D. Walton H. H. Sutherland and J. H. C. Hogg Acta Cryst.,1978 B34 41. 19' 19' 19' The Typical Elements 207 The structure is built up of a puckered cubic close-packed arrangement of sulphur atoms both the indium and phosphorus atoms being tetrahedrally co-ordinated by sulphur; d(1n-S) = 2.480 A. The sulphur atoms in In4(P2S6)3 are also cubic close packed but with the indium atoms and P2 groups occupying the octahedral holes; average In-S distance = 2.657 A.204 5 Thallium The reaction between thallium(II1) and hydrogen peroxide Tl"' + H202+ TI' + O2+ 2H' has been followed iodimetrically and by edta titration; it was found to be independent of thallium(1) ions but was inhibited by sulphate and chloride ions as well as monomers and radical scavengers.The mechanism could be explained at least partly by a one electron reaction of mono-and di-(hydrogen-peroxo)thallium(IIr) species with hydrogen peroxide2" e.g. T1(02H)'++ H202-D T1++ O2+ H202+ H+. Thallium(1) sulphite made by passing a stream of sulphur dioxide through a saturated solution of thallium(1) carbonate under an inert atmosphere possesses a structure containing two different co-ordination positions for the thallium average T1-0 distances were 3.0118 and 2.797 A close to the sum of the ionic radii for T1' and 0'-.The difference Fourier map revealed that the sulphur was apparently surrounded by four equivalent oxygens showing a disordered structure in which the sulphite ion could be considered a free rotator.206 Discrete molecules of T1(NO3),(H20), linked by hydrogen-bonding occur in crystalline thallium(II1) nitrate trihydrate. The thallium atom is chelated by three bidentate nitrate groups (Tl-0 = 2.299 2.637 A) and by three water molecules (Tl-0 = 2.293 A) giving rise to tricapped trigonal prismatic co-ordination in which the three equatorial distances are significantly longer (2.64A) than the distances to the corners of the prism (2.29A). The nitrate ion is distorted from D, symmetry by the different bonding environments of the three oxygen^.^^^ In thallium(II1) triacetate the thal- lium atom is chelated by three acetate groups (Tl-0 = 2.26-2.34 A) and forms two further bonds (2.57A) to adjacent molecules along the c axis thus linking the molecules into chains."* A convenient synthesis for TlOBr which is isomorphous with InOBr is to treat thallium(1) carbonate with liquid bromine; if bromine vapour is used the products are T1203 TlzBr4 and T1Br.'09 The new oxothallate(II1) Na5T104 has been made as a yellow solid by heating a mixture of sodium oxide and thallium(II1) oxide (ratio 5.4 1)in a silver cylinder at 620 "Cfor 7 days.Thermal decomposition yields first the yellow Na,TIO and then red NaT1_02.2'0 Thallium(1) sulphide and germanium 204 R.Diehl and C.-D. Carpentier Actu Cryst. 1978 B34 1097. 2os Z. Boti I. Horvath Z. Szil and L. J. Csanyi J.C.S. Dalton 1978 1012. 206 Y. Oddon G. Pepe J.-R. Vignalou and A. Tranquard J. Chem. Res. (S),1978,250. '07 R. Faggiani and I. D. Brown Acru Cryst. 1978 B34 1675. 208 R. Faggiani and I. D. Brown Actu Cryst.,1978 B34 2845. 209 J. R. Giinter 2. unorg. Chem. 1978,438,203. *lo R. Hoppe and D. Fink Z. anorg. Chem. 1978,443 193. F. A.Hart A. G. Massey P. G. Harrison and J. H. Holloway disulphide when heated in a 1:1 ratio at 500 "C give the thiogermanate Tl,Ge,S the structure of which is characterized by Ge2S64- anions held together by T1' cations. The anions consist of two GeS4 tetrahedra sharing an edge and the cations are surrounded by either seven or eight sulphur atoms at distances ranging from 3.024 A to 3.734 A.211 When T1' ions are trapped in the polar cavity of the polyether dibenzo-18-crown- 6 a strong interaction appears to occur between the metal ion and the aromatic rings of the ether as judged by fluorescence quenching and n.m.r.studies.212