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.