CHEMISTRY OF POLYNUCLEAR METAL-COMPLEXES WITH BRIDGING CARBENE OR CARBYNE LIGANDS .111. PROTONATION OF THE SALTS [NET4][M(=CR)(CO)2(ETA-X-C2BNHNME2)] (M=MO OR W, R=ME OR C6H4ME-4, X=5,N=9,X=6,N=10) IN THE PRESENCE OF THE ALKYLIDYNEMETAL COMPOUNDS [M(=CR)(CO)2-(ETA-C5H5)], CRYSTAL-STRUCTURES OF [W2(MU-CME)(CO)3(ETA-5-C2B9H8(CH2C6H4ME-4)ME2)(ETA-C5H5)], [W2(MU-CC6H4ME-4)-(CO)3(ETA-5-C2B9H9ME2)(ETA-C5H5)] AND [MOW(MU-CC6H4ME-4)-(CO)2(PME3)(ETA-6-C2B10H10ME2)(ETA-5-C5H5)]

Treatment of mixtures of [NEt4][W(= CC6H4Me-4) (CO)2(eta-5-C2B9H9Me2)] and [M(= CR)(CO)2(eta-C5H5)](M = W, R = Me; M = Mo, R = C6H4Me-4) in CH2Cl2 at -78-degrees-C with HBF4.Et2O affords, respectively, the complexes [MW(mu-CR)(CO)3{eta-5-C2B9H8(CH2C6H4?? Me-4)Me2{(eta-5-C5H5)]. The structure of the ditungsten compound was determined by X-ray crystallography. The W-W bond [2.651 (1) angstrom] is spanned essentially symmetrically by the ethylidyne group [mu-C-W 1.95(1) and 2.03(1) angstrom]. One W atom is co-ordinated by two CO groups and the open pentagonal face of a nido-icosahedral C2B9 cage. A boron atom in the beta site of the activated CCBBB face carries a CH2C6H4Me-4 substituent, and a BH group in the face alpha to the carbon atoms forms an exopolyhedral B-H half arrow pointing to the right W bond to the other tungsten, which carries a CO molecule and the C5H5 ring. In contrast, protonation of a mixture of [NEt4][W(= CC6H4Me-4)(CO)2(eta-5-C2B9H9Me2)] and [W(= CC6H4Me-4)(CO)2(eta-C5H5)] yields the complex [W2(mu-CC6H4Me-4)(CO)3(eta-C2B9H9Me2)(eta-C5H?? 5)]. The latter in toluene at 80-degrees-C undergoes a polytopal rearrangement affording an isomer in which the nido-icosahedral C2B9H9Me2 fragment has a 7,9-C2 rather than the 7,8-C2 configuration present in the [C2B9H9Me2]2-dianion in the precursor. This was confirmed by an X-ray diffraction study on the 7,9 isomer, which was also obtained by treating a mixture of [NEt4][W(= CC6H4Me-4)(CO)2(eta-6-C2B10H10Me2)] and [W(= CC6H4Me-4)(CO)2(eta-C5H5)] in CH2CI2 at -78-degrees-C with HBF4.Et2O. This is a remarkable 13- to 12-vertex cage degradation process. In both isomers of [W2(mu-CC6H4Me-4)(CO)3(eta-5-C2B9H9Me2)(eta-C5H5)] the metal-metal bonds are spanned by B-H half arrow pointing to the right W three-centre two-electron bonds as well as p-tolylmethylidyne groups. Protonation of a mixture of [NEt4][W(= CC6H4Me-4)(CO)2(eta-6-C2B10H10Me2)] and [Mo(= CC6H4Me-4)(CO)2(eta-C5H5)] gave two dimetal compounds: [MoW(mu-CC6H4Me-4)(CO)3(eta-5-7,9-C2B9H9Me2) (eta-C5H5)] and [MoW(mu-CC6H4Me-4)(CO)3(eta-6-C2B10H10Me2)(eta-C5H5)]. Treatment of the latter with PMe3 yields [MoW(mu-CC6H4Me-4)(CO)2(PMe3)(eta-6-C2B10H10Me2)(eta-C5H5)], the structure of which has been determined by X-ray diffraction. The Mo-W bond [2.702(1) angstrom] is bridged on one side by the CC6H4Me-4 group [mu-C-Mo 1.94(1), mu-C-W 2.10(1) angstrom] and on the other by the C2B10H10Me2 cage. The latter is eta-6 co-ordinated to the W atom via an open activated CBCBBB face, and this metal atom also carries two CO ligands. The boron atom activated CBCBBB in the face of the cage which is in a beta site with respect to the carbons forms an exopolyhedral B-H half arrow pointing to the right Mo bond across the Mo-W bond. The Mo atom is co-ordinated by the PMe3 lignad [Mo-P 2.496 (4) angstrom] and the C5H5 ring. The NMR data (H-1, C-13-{H-1}, B-11-{H-1}, P-31-{H-1}) for the new complexes are reported and discussed.