Mixed-metal cluster chemistry. 24. Isocyanide derivatives of [MoIr3(μ-CO)3(CO)8(η-C5H5)] and [Mo2Ir2(μ-CO)3(CO)7(η-C5H5)2];: X-ray crystal structures of [MoIr3(μ-CO)3(CO)7(L)(η-C5H5)] (L=CNBut, CNC6H3Me2-2,6) and [Mo2Ir2(μ-CO)2(CNBut)2(CO)6(η-C5H5)2]

Reactions of MoIr3(μ-CO)3(CO)8(η-C5H5) (1) with stoichiometric amounts of isocyanides afford the ligand-substituted clusters [MoIr3(μ-CO)3(CO)8−n(L)n(η-C5H5)] (L=CNBut, n=1 (3), 2 (4), 3 (5); L=CNC6H3Me2-2,6, n=1 (6), 2 (7), 3 (8)) in moderate to excellent yields (13–75%). Single-crystal X-ray studies of 3 and 6 reveal that the isocyanides occupy coordination sites on an apical cluster core metal atom, a first for ligand-substituted derivatives of 1. In contrast, reaction of Mo2Ir2(μ-CO)3(CO)7(η-C5H5)2 (2) with one or two equivalents of CNBut affords Mo2Ir2(μ-CO)2(CNBut)2(CO)6(η-C5H5)2 (9) as the only major product. A single-crystal X-ray study of 9 reveals an unprecedented carbonyl configuration about the pseudotetrahedral cluster core.