Synthesis of carbaborane rhodium–platinum complexes: crystal structure of [RhPt(µ-H)(µ-CO)(PEt3)2(PPh3)(η5-7,9-C2B9H11)]

Abstract

Treatment of [PtCl(H)(PEt₃)₂] with [NEt₄][Rh(CO)(PPh₃)(η⁵-7,9-C₂B₉H₁₁)] in thf (tetrahydrofuran) in the presence of TlBF₄ affords [RhPt(µ-H)(µ-CO)(PEt₃)₂(PPh₃)(η⁵-7,9-C₂B₉H₁₁)], the structure of which has been established by X-ray diffraction. On heating at reflux in thf for several days the compound yields [RhPt(µ-σ:η⁵-7,9-C₂B₉H₁₀)(CO)(PEt₃)₂(PPh₃)], a product in which the rhodium–platinum bond is spanned by an exopolyhedral cage B–Pt linkage. Reactions between the platinum compounds [PtCl(R)L₂](R = Me or Ph; L = PEt₃, PPh₃ or PMe₂Ph) and [NEt₄][Rh(CO)(PPh₃)(η⁵-7,n-C₂B₉H₁₁)](n= 8 or 9) afford several dimetal complexes in which the Rh–Pt bonds are bridged by exopolyhedral cage B–H ⇀ Pt or B–Pt bridge bonds. The latter are formed from the former by loss of RH molecules, and this process is favoured for Rh(η⁵-7,9-C₂B₉H₁₁)versus Rh(η⁵-7,8-C₂B₉H₁₁), and in the order L = PPh₃ < PMe₂Ph < PEt₃ for the ligands on platinum. The NMR data (¹H, ¹³C-{¹H}, ¹¹B-{¹H} and ³¹P-{¹H}) are reported and discussed in relation to the structures of the products.