Mixed-metal cluster chemistry VIII¹: Phosphite substitution at [CpWIr₃(CO)₁₁]; X-ray crystal structure of [CpWIr₃(μ-CO)₃(CO)₆{P(OPh)₃} ₂]

Reactions of [CpWIr₃(CO)₁₁] (1) with stoichiometric amounts of phosphites afford the substitution products [CpWIr₃(μ-CO)₃(CO)_8-n(L)_n] [L=P(OMe)₃, n=1 (2), 2 (3), 3 (4); L=P(OPh)₃, n=1 (5), 2 (6), 3 (7)] in fair to excellent yields (29-71%). Clusters 2, 4, 5 and 7 are fluxional in solution, with the interconverting isomers resolvable at low temperatures. A structural study of 6 reveals that the three edges of a WIr₂ face of the tetrahedral core are spanned by bridging carbonyls, and that iridium-bound triphenylphosphites ligate radially and axially and the tungsten-bound cyclopentadienyl coordinates axially with respect to this WIr₂ face. Information from this crystal structure, ³¹P-NMR data, and results with analogous triphenylphosphine-ligated tungsten-triiridium clusters have been employed to suggest coordination geometries for the isomers.