TRICARBONYL(CARBABORANE) COMPLEXES OF THE GROUP-6 METALS AS REAGENTS FOR PREPARING HETERONUCLEAR DIMETAL COMPOUNDS INVOLVING PLATINUM

The reagents Tl2[M(CO)3(eta5-C2B9H9Me2)] (M = Cr, Mo or W), generated in situ from TI[TlC2B9H9Me2] and [M(CO)3(NCMe)3], react in thf (tetrahydrofuran) with the compounds [PtCl2L2] (L = PPh3 or PEt3) to give the dimetal complexes [MPt(CO)3L2(eta5-C2BH9Me2)]. NMR studies revealed that the tungsten-platinum species were produced as a mixture of two isomers of formulation [WPt(CO)3L2(eta5-C2B9H9Me2)] and [WPt(mu-H)(mu-sigma:eta5-C2B9H8Me2)(CO)3L2]. The complexes [MPt(CO)3L2(eta6-C2B10H10Me2)] have been prepared from reactions between [PtCl2L2] and Na2[M(CO)3(eta6-C2B10H10Me2)] (M = Mo or W), with the latter generated in situ from Na2[C2B10)H10Me2] and [M(CO)3(NCMe)3]. Similar reactions using [PtCl2(cod)] (cod = cycloocta-1,5-diene), followed by addition of PPh3 to the reaction mixture, afforded the salts [PtH(PPh3)3][MPt(mu-sigma:eta6-C2B10HMe2)(CO)4(PPh3)]. Protonation (HBF4.Et2O) of the latter yields the complexes [MPt(CO)4(PPh3)(eta6-C2B10H10Me2)]. An X-ray crystallographic study of the molybdenum-platinum compound revealed that the molecule contained a Mo-Pt bond [2.814(1) angstrom] spanned by the nido-C2B10H10Me2 cage such that the latter is eta6-co-ordinated to the molybdenum and linked to the platinum via a three-centre two-electron B-H-Pt bond. This bond involves the hydrogen atom attached to the boron atom which is beta to the carbons in the CBCBBB face of the cage ligating the molybdenum atom. The NMR data (H-1, C-13-{H-1}, P-31-{H-1} and B-11-{H-1}) for the new compounds are discussed in relation to the structures proposed.