CHEMISTRY OF POLYNUCLEAR METAL-COMPLEXES WITH BRIDGING CARBENE OR CARBYNE LIGANDS .109. REACTIONS OF TUNGSTEN MOLYBDENUM DIMETAL COMPOUNDS BEARING CARBABORANE LIGANDS WITH ALKYNES - CRYSTAL-STRUCTURE OF [MOW(MU-C4ME4)(SIGMA,ETA-5-CH(C6H4ME-4)C2B9H8ME2)(ETA-C7H7)]

Treatment of the compounds [MoW(mu-CR) (CO)2(eta-C7H7)(eta-5-C2B9H9Me2)] in thf (tetrahydrofuran) with the alkynes MeC = CMe or EtC = CEt affords the complexes [MoW(mu-CR)(CO)(eta-R'C2R')(eta-C7H7)(eta-5-C2B9Me2)?? ] (R = C6H4Me-4, R' = Me; R = C = CBu(t), R' = Me or ET). Similar reactions between [MoW(mu-CC6H4Me-4) (CO)2(eta-C7H7)(eta-5-C2B9H10Me)] and MeC = CMe or PhC = CPh yield the related species [MoW(mu-CC6H4Me-4)(CO)(eta-R'C2R')(eta-C7H7) (eta-5-C2H2B9H10Me)] (R' = Me or Ph). The reaction of [MoW(mu-CC6H4Me-4)(CO)(eta-MeC2Me)(eta-C7H7) (eta-5-C2B9H9Me2)] with MeC = CMe in toluene at 100-degrees-C gives a novel dimetal complex [MoW(eta-C4Me4) {delta, eta-5-CH(C6H4Me-4)C2B9H8Me2}(eta-C7H7)], the structure of which was established by X-ray diffraction. The Mo-W bond [2.922(1) angstrom] is symmetrically bridged by al mu-C4Me4 fragment, the carbon atoms of which are linked to both metal atoms in the eta-4 fashion. The molybdenum atom carries the eta-C7H7 ligand, and the tungsten atom is ligated by a CH(C6H4Me-4)C2B9H8Me2 fragment. In the latter the CH(C6H4Me-4) moiety forms a bridge between the tungsten [W-C 2.226(8) angstrom) and a boron atom [B-C 1.54(1) angstrom] in the pentagonal face of the cage. This boron atom is in the beta site BAR(BBBCC) with respect to the carbon atoms, and all the atoms of the ring are bonded to the tungsten, but the connectivities are somewhat asymmetric [2.227(9)-2.472(9) angstrom]. The H-1 and C-13-{H-1} NMR data for the new compounds are reported and discussed.