Mixed-metal cluster chemistry 25: Mixed ligand derivatives of MoIr3(μ-CO)3(CO)8(η-C5R5) (R=H, Me) and Mo2Ir2(μ-CO)3(CO)7(η-C5H5)2; X-ray crystal structures of MoIr3(μ-CO)3(CO)6(PPh3)2(η-C5Me5) and Mo2Ir2(μ4-η2-PhC2Ph)(μ-CO)4(CNBut)(CO)3(η-C5H5)2

Reactions of MoIr3(μ-CO)3(CO)8(η-C5Me5) (1) with stoichiometric amounts of the isocyanide ButNC afford the ligand substituted clusters MoIr3(μ-CO)3(CNBut)n(CO)8−n(η-C5Me5) (n=1 (2), 2 (3), 3 (4)) in fair to good yields (13–58%). In contrast, 1 reacts with PPh3 to afford a single unexpected product, namely MoIr3(μ-CO)3(CO)6(PPh3)2(η-C5Me5) (5). A single-crystal X-ray study of 5 reveals that the phosphines occupy coordination sites adjacent to the plane of bridging carbonyls in a radial–radial–axial conformation previously unobserved in structural studies of molybdenum–tri-iridium or tungsten–tri-iridium clusters. Reactions of Mo2Ir2(μ-CO)3(CO)7(η-C5H5)2 (6) with ButNC or diphenylacetylene proceed cleanly in high yield to afford Mo2Ir2(μ-CO)2(CNBut)2(CO)6(η-C5H5)2 (7) or Mo2Ir2(μ4-η2-PhC2Ph)(μ-CO)4(CO)4(η-C5H5)2 (8), respectively; reacting 7 with diphenylacetylene or 8 with ButNC results in a more complex mixture of products from which Mo2Ir2(μ4-η2-PhC2Ph)(μ-CO)4(CNBut)(CO)3(η-C5H5)2 (9) can be isolated in low yield.