Reactions of [NEt4][10-endo-{Au(PPh3)}-nido-7,8-C2B9H9Me2]: carbaborane cage transfer from gold to iridium

Abstract

The salt [NEt₄][10-endo-{Au(PPh₃)}-nido-7,8-C₂B₉H₉Me₂] reacts with trans-[IrCl(CO)(PPh₃)₂] in thf (tetrahydrofuran), in the presence of TIBF₄, to afford the complex [IrAu(CO)(PPh₃)₂(η⁵-7,8-C₂B₉H₉Me₂)]. The structure of this product was established by X-ray crystallography. The iridium is co-ordinated on one side by the open pentagonal face of a nido-icosahedral 7,8-C₂B₉H₉Me₂ group in an η⁵ bonding mode, and on the other by the PPh₃ and CO ligands and an Au(PPh₃) fragment [Ir–Au 2.616(2), Au–P 2.251(3)Å, Ir–Au–P 175.8(1)°]. The related compound [IrAu(CO)₂(PPh₃)(η⁵-7,8-C₂B₉H₉Me₂)] is formed in the corresponding reaction using cis-[IrCl(CO)₂(NH₂C₆H₄Me-4)]. Small and variable amounts of a metal cluster species [Ir₂Au₄(µ-σ:η⁵-7,8-C₂B₉H₈Me₂)(CO)₃(PPh₃)₄][7,8-C₂B₉H₁₀Me₂] are also produced in the latter reaction. Treatment of [IrCl(PPh₃)₃] with [NEt₄][10-endo-{Au(PPh₃)}-nido-7,8-C₂B₉H₉Me₂] affords the dimetal complex [IrAuH(µ-σ:η³-7,8-C₂B₉H₈Me₂)(PPh₃)₃], the structure of which was determined by X-ray crystallography. The Ir–Au bond [2.739(1)Å] is spanned by a 7,8-C₂B₉H₈Me₂ group. The open [graphic omitted] pentagonal ring of the cage is attached to the iridium via its three boron atoms, while also being σ bonded to the gold atom through the boron atom in the β site with respect to the two carbons [Au–B 2.200(9)Å]. The gold atom carries a PPh₃ ligand [Au–P 2.320(2)Å, P–Au–Ir 164.6(1)°], and the iridium is co-ordinated by two such groups [Ir–P 2.293 Å(average), P–Ir–P 100.3(1)°] and a hydride ligand transoid to the gold [Ir–H 1.58(9)Å, H–Ir–Au 168(3)°]. The NMR data (¹H, ¹³C-{¹H}, ³¹P-{¹H} and ¹¹B-{¹H}) of the new compounds are reported and discussed in relation to the structures.