Gacsh prepared directly from gac13 and an excess of

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Unformatted text preview: example of InMe3 accepting three lone pairs of electrons rather than the more usual one or two.@') The structure (Fig. 7.20b) features a shallow InC3 pyramid with C-In-C angles of 114"- 117" and extremely acute N-In-N angles (48.6") associated with the long In-N bonds (278pm). The three P t groups are all in equatorial positions. Cyclopentadienyl and arene complexes of Ga, In and T1 have likewise attracted increasing attention during the past decade and provide a rich variety of structural types and of chemical diversity. [Ga(CsH&], prepared directly from GaC13 and an excess of LiC5H5 in Et20, was found to have simple trigonal planar Ga bonded to three q1-C5H5 groups. The more elusive C5Me5 derivative was finally prepared from GaC13 and an excess of the more reactive NaCsMe5 in thf solution, or by reduction of Ga(C5Me5)nC13-n ( n = 1 ,2) with sodium naphthalenide in thf.(82) [Ga(CsMes)s] H. SCHUMA", U . HARTMANN, A. DIETRICH and J. RCKARDT, Angew. Chem. Int. Edn. Engl. 27, 1077-8 " D . C. BRADLEY, D. M. FRIGO, I. S. HARDING, M. B . HURSTHOUSE M. MOTEVALLI, Chem. SOC.,Chem. and J. Commun., 577-8 (1992). 82 0. T. BEACHLEY R . B . HALLOCK,rganometallics 6, and O (1988). 170-2 (1987). Figure 7.20 (a) Structure of [ &(CH2)3N] showing trigonal planar monopyramidal 4-fold coordination about Ga and tetrahedral coordination about N. (b) Structure of [Me31n(q3-(PfNCH2)3)]- see text for dimensions. (c) Structure of polymeric [In(q5-C,H,)]. Aluminium, Gallium, Indium and Thallium 264 is a colourless, sublimable, crystalline solid, mp 168", and appears to be a very weak Lewis acid. As distinct from the cyclopentadienyls of Ga"', those of In and T1 involve the +1 oxidation state of the metal and pentahapto bonding of the ligand. [In($-CsH,)] is best prepared by metathesis between LiC5H5 and a slurry of InCl i n E t20.@3)It is monomeric in the gas phase with a 'half-sandwich' structure, the In-Cg(centroid) distance being 232 pm, but in the solid state it is a zig-zag polymer with significantly larger In-Cs(centroid) distances as shown in Fig. 7 . 2 0 ~ . ( ~ ~ ) crystalline The pentamethyl derivative, by contrast, is hexameric and features an octahedral In6 cluster each vertex of which is ~5-coordinatedby C5Me5. ( 8 5 ) [TI($-C5H5)] precipitates as air-stable yellow crystals when aqueous TlOH is shaken with cyclopentadiene. In the gas phase the compound is monomeric with C5v symmetry, the T1 atom being 241 pm above the plane of the ring (microwave), whereas in the crystalline phase there are zig-zag chains of equispaced alternating 83 C. PEPPE, . G. TUCK D and L. VICTORIANO,Chem. SOC., J. Dalton Trans., 2592 (1981). 840. . BEACHLEY, J. C. PAZIK, T T. E. GLASSMAN, M. R. CHURCHILL,C. FEITINCER R. BLOM,OrgunoJ. and metullics 7 , 1051-9 (1988). " 0 . T. BEACHLEY, R. CHURCHILL, . C. FETTINGER, M. J J. C. PAZIKand L. VICTORIANO, Am. Chem. SOC. 108, J. 4666-8 (1986). Figure 7.21 ( a) The 'half-sandwich' Ch. 7 C5H5 rings and T1 atoms similar to the In homologue. Hexaha...
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This note was uploaded on 10/12/2012 for the course CHEMISTRY CHM1040 taught by Professor Jhon during the Spring '12 term at Florida A&M.

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