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

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)A, 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)A] 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)A]. The gold atom carries a PPh3 ligand [Au–P 2.320(2)A, P–Au–Ir 164.6(1)°], and the iridium is co-ordinated by two such groups [Ir–P 2.293 A(average), P–Ir–P 100.3(1)°] and a hydride ligand transoid to the gold [Ir–H 1.58(9)A, 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.