CHEMISTRY OF POLYNUCLEAR METAL-COMPLEXES WITH BRIDGING CARBENE OR CARBYNE LIGANDS .110. SYNTHESIS OF COMPOUNDS WITH TUNGSTEN COPPER OR GOLD BONDS - CRYSTAL-STRUCTURE OF [NET4][W2CU(MU-CC=CBUT)2(CO)4(ETA-5-C2B9H9ME2)2].ET2O

Treatment of the reagents [NEt4][W(= CR)(CO)2(eta-5-C2B9H9Me2)] in CH2Cl2 with 1 equivalent of CuCl or [AuCl(tht)] (tht = tetrahydrothiophene) affords the labile complexes [NEt4][WMCI(mu-CR)(CO)2-(eta-5-C2B9H9Me2)] (M = Cu or Au, R = C6H4Me-4 or C = CBu(t)). Use of 2 equivalents of CuCl yields the stable tungstendicopper species [NEt4][WCu2Cl2(mu-3-CR)(CO)2(eta--5C2B9H9Me2)], which may also be obtained by adding 1 equivalent of CuCl to the tungsten-copper dimetal compounds in CH2Cl2. Reactions of the salts [NEt4][WCuCl(mu-CR)(CO)2(eta-5-C2B9H9Me2)] with CNR' in CH2Cl2 in the presence of TIBF4 yields the neutral complexes [WCu(mu-CR)(CO)2(CNR')(eta-5-C2B9H9Me2)] (R = C6H4Me-4 or C = CBu(t), R' = C6H3Me2-2,6; R = C = CBu(t), R' = Bu(t)). The trimetal compounds [NEt4][W2-M(mu-CR)2(CO)4(eta-5-C2B9H9Me2)2] (M = Cu, R = C6H4Me-4 or C = CBu(t); M = Au, R = C = CBu(t)) have been prepared by treating in CH2Cl2, 2 equivalents of the reagents [NEt4][W(= CR)(CO)2(eta-5-C2B9H9Me2)] with 1 equivalent of CuCl or [AuCl(tht)] in the presence of TIBF4. An X-ray diffraction study of the salt [NEt4][W2Cu(mu-CC = CBu(t))2(CO)4(eta-5-C2B9H9Me2)2] revealed a novel structure in the crystal. The anion has a W2Cu spine [W-Cu 2.602(1) and 2.764(1) angstrom, W-Cu-W 152.7(1)degrees] with each metal-metal bond asymmetrically bridged by a CC = CBu(t) group [mu-C-W 1.85(1), mu-C-Cu(av.) 2.08(1) angstrom; W-mu-C-CCBu(t)(av.) 169.5(1)degrees]. The shorter of the two W-Cu separations is also spanned by a C2B9H9Me2 cage. As expected the latter is eta-5 co-ordinated to the tungsten atom, but it also forms an exopolyhedral B-H half-arrow-pointing-right Cu three-centre two-electron bridge bond employing the boron atom beta to the carbon atoms in the pentagonal CCBBB face of the cage [mu-B-W 2.36(1), mu-B-Cu 2.33(1) angstrom]. The other tungsten atom is ligated by a C2B9H9Me2 group in the normal eta-5 bonding mode, and both tungstens carry two terminally bound CO groups. The reaction between [W(= CC = CBu(t))(CO)2(eta-C5H5)] and [Pt(nb)3] (nb = norbornene = bicyclo[2.2.1]heptene) affords the compound [W2Pt(mu-CC = CBu(t)2(CO)4(eta-C5H5)2]. The H-1 and C-13-{H-1} NMR data for the new compounds are reported and discussed.