CHEMISTRY OF POLYNUCLEAR METAL-COMPLEXES WITH BRIDGING CARBENE OR CARBYNE LIGANDS .112. SYNTHESIS OF RHENIUM-RHODIUM COMPLEXES - CRYSTAL-STRUCTURE OF [RERH[MU-SIGMA,ETA-5-C2B9H7(CH2C6H4ME-4)ME2](CO)4(ETA-C5H4ME)]

Treatment of [NEt4][Rh(CO)2(eta-5-C2B9H9Me2)] in CH2Cl2 with [Re(= CC6H4Me-4)(CO)2(eta-C5H4Me-4)]-[BCl4] affords the dimetal complex [ReRh{mu-sigma,eta-5-C2B9H7(CH2C6H4Me-4)Me2}(CO)4(eta-C5H4Me)]. The structure was established by X-ray diffraction. The Re-Rh bond [2.888(1) angstrom] is spanned by the C2B9H7(CH2C6H4Me-4)Me2 fragment. The open pentagonal face of the C2B9 cage is eta-5 co-ordinated to the rhodium, and there is an exopolyhedral B-Re [2.17 (2) angstrom] sigma-bond involving a boron atom in the alpha-site with respect to the carbon atoms in the activated CCBBB ring; the boron atom in the beta-site activated CCBBB carries the CH2C6H4Me-4 substituent. The rhenium and rhodium atoms are each ligated by two terminally bound CO molecules, and the rhenium is also co-ordinated by the eta-C5H4Me group. The related complexes [ReRh{mu-sigma,eta-5-C2B9H7(CH2C6H4Me-4)Me2}(CO)3L(eta-C5H5)] (L = CO or PMe2Ph) have also been prepared. In contrast with the aforementioned results the complex [Mn(= CC6H4Me-4)-(CO)2(eta-C5H4Me)][BCl4] reacts with [NEt4][Rh(CO)(PPh3)(eta-5-C2B9H9Me2)] and [NEt4][Rh(cod)-(eta-5-C2B9H9Me2)] (cod = cycloocta-1,5-diene) to give the mononuclear rhodium species [Rh{sigma,eta-5-CH(C6H4Me-4)C2B9H8Me2}(CO)(PPh3)] and [Rh{sigma,eta-5-CH(C6H4Me-4)C2B9H8Me2}(cod)], respectively. The NMR data (H-1,C-13-{H-1}, B-11-{H-1}) for the new complexes are reported and discussed.