SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF THE COMPOUNDS [WCOAU(MU-3-CC6H4ME-4)(CO)2(PPH3)(ETA-5-C5ME5)(ETA-6-C2B10H10ME2)] AND [MOCO(MU-CC6H4ME-4)(CO)2(ETA-4-C4ME4)(ETA-6-C2B10H10ME2)] AND STUDIES ON RELATED MIXED-METAL COMPLEXES

The compounds [Co(C2H4)2(eta-5-C5Me5)] and [NEt4][M( = CC6H4Me-4)(CO)2(eta-6-C2B10H10Me2)] (M = Mo, W) react in CH2Cl2 to afford the salts [NEt4][MCo(mu-CC6H4Me-4)(CO)2(eta-5-C5Me5)(eta-6-C2B10H10Me2)]. Protonation (HBF4.Et2O) of these species yields the dimetal compounds [MCo(mu-CC6H4Me-4)(mu-sigma:eta-6-C2B10H9Me2)(CO)2(eta-5-C5Me5)], while treatment with [AuCl(PPh3)] in tetrahydrofuran in the presence of TIBF4 yields the trimetal complexes [MCoAu(mu-3-CC6H4Me-4)(CO)2(PPh3)(eta-5-C5Me5)(eta-6-C2B10H10Me2)]. The structure of the species with M = W has been established by X-ray diffraction. Crystals are triclinic, space group P1BAR (No. 2) with a = 10.007 (4) angstrom, b = 10.791 (3) angstrom, c = 21.642 (7) angstrom, alpha = 87.81 (2)-degrees, beta = 84.58 (3)-degrees, gamma = 73.10 (2)-degrees, and Z = 2. The core of the molecule consists of a metal triangle [Au-W 2.855 (2), Au-Co 2.603 (3), W-Co 2.576 (3) angstrom] that is asymmetrically capped by the p-tolylmethylidyne group [mu-3-C-Au 2.39 (2) angstrom, mu-3-C-W 2.01 (2) angstrom, mu-3-C-Co 1.91 (2) angstrom.] The gold and cobalt atoms carry PPh3 and eta-4-C4Me4 ligands, respectively. The tungsten atom is eta-6 coordinated by the open face of the nido-C2B10H10Me2 fragment and by the two carbonyl groups. One carbonyl ligand semibridges the W-Co bond [W-C-O 166 (2)-degrees]. The cobalt complex [Co(CO)2(NCMe)(eta-4-C4Me4)][PF6] reacts with the salts [NEt4][M( = CC6H4Me-4)(CO)2(eta-6-C2B10H10Me2)] in CH2Cl2 to afford the compounds [MCo(mu-CC6H4Me-4)(CO)2(eta-4-C4Me4)(eta-6-C2B10H10Me2)]. An X-ray diffraction study on the dimetal complex with M = Mo revealed that the crystals were monoclinic, space group P2(1)/c (No. 14) with a = 16.276 (2) angstrom, b = 11.870 (2) angstrom, c = 15.791 (4) angstrom, beta = 112.60 (2)-degrees, and Z = 4. The metal-metal bond [2.540 (1) angstrom] is bridged on one side by the alkylidyne group [mu-C-Mo 1.914 (7), mu-C-Co 1.915 (6) angstrom] and on the other by the nido-C2B10H10Me2 cage. The open face of the latter is eta-6 coordinated to the Mo atom, while the BH group, which is in the beta site with respect to the carbon atoms in the activated CBCBBB ring, forms an exo-polyhedral B-H half arrow pointing right Co bond. The cobalt atom carries the eta-4-C4Me4 ligand, and the molybdenum atom is ligated by two CO groups, as expected. Reactions between [Co(CO)2(NCMe)(eta-4-C4Me4)][PF6] and the salts [NEt4][M(= CR)(CO)2(eta-5-C2B9H9Me2)] afford the dimetal compounds [MCo(mu-CR)(CO)3(eta-4-C4Me4)(eta-5-C2B9H9Me2)] (M = Mo, W, R = C6H4Me-4; M = W, R = Me).