Chemistry of polynuclear metal complexes with bridging carbene or carbyne ligands. Part 112. Synthesis of rhenium–rhodium complexes; crystal structure of [ReRh{µ-σ,η⁵-C₂B₉H₇(CH₂C₆H₄Me-4)Me₂}(CO)₄(η-C₅H₄Me)]

Abstract

Treatment of [NEt4][Rh(CO)2(η5-C2B9H9Me2)] in CH2Cl2 with [Re(CC6H4Me-4)(CO)2(η-C5H4Me-4)]-[BCl4] affords the dimetal complex [ReRh{µ-σ,η5-C2B9H7(CH2C6H4Me-4)Me2}(CO)4(η-C5H4Me)]. The structure was established by X-ray diffraction. The Re–Rh bond [2.888(1)Å] is spanned by the C2B9H7(CH2C6H4Me-4)Me2 fragment. The open pentagonal face of the C2B9 cage is η5 co-ordinated to the rhodium, and there is an exopolyhedral B–Re [2.17(2)Å]σ bond involving a boron atom in the α site with respect to the carbon atoms in the [graphic omitted] ring; the boron atom in the β site [graphic omitted] 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 η-C5H4Me group. The related complexes [ReRh{µ-σ,η5-C2B9H7(CH2C6H4Me-4)Me2}(CO)3L(η-C5H5)](L = CO or PMe2Ph) have also been prepared. In contrast with the aforementioned results the complex [Mn(CC6H4Me-4)(CO)2(η-C5H4Me)][BCl4] reacts with [NEt4][Rh(CO)(PPh3)(η5-C2B9H9Me2)] and [NEt4][Rh(cod)(η5-C2B9H9Me2)](cod = cycloocta-1,5-diene) to give the mononuclear rhodium species [Rh{σ,η5-H(C6H4Me-4)C2B9H9Me2}(CO)(PPh3)] and [Rh{σ,η5-CH(C6H4Me-4)C2B9H8Me2}(cod)], respectively. The NMR data (1H, 13C-{1H}, 11B-{1H}] for the new complexes are reported and discussed.