Synthesis and structural characterization of the phosphido cluster [Ir4H(CO)10(µ-PPh2)] and its facile carbonyl substitution reactions with a series of phosphines and phosphites
Abstract
The tetranuclear cluster [Ir4H(CO)10(µ-PPh2)]1 is formed from [Ir4(CO)11(PPh2)]2 by deprotonation, which yields [Ir4(CO)10(µ-PPh2)]–3, followed by protonation of the anion. It has been fully characterized by an X-ray analysis, and exhibits a tetrahedral arrangement of metal atoms with the three basal edges bridged by a phosphido, a hydrido and a carbonyl ligand. Both 1 and 3 undergo facile carbonyl substitution reactions with phosphites and phosphines L [PPh3, PPhMe2, P(OPh)3 or P(C6H4X-4)3(X = F, Cl, Me, 4-Ome or 2-OMe)] to give [Ir4H(CO)9L(µ-PPh2)]4a–4h and [Ir4(CO)9L(µ-PPh2)]–5a–5h respectively, the latter being converted into the corresponding hydride derivatives by protonation. Further substitution of a CO in 4a–4h affords [Ir4H(CO)8L2(µ-PPh2)]6a–6h. An X-Ray analysis of [Ir4H(CO)9(PPh3)(µ-PPh2)]4a shows that carbonyl substitution has occurred at a basal Ir atom which is not bridged by the phosphido ligand.