Syntheses of pentanuclear group 6 iridium clusters by core expansion of tetranuclear clusters with Ir(CO)2(η5-C5Me4R) (R = H, Me).

Metal cluster core expansion at tetrahedral group 6–group 9 mixed-metal clusters MIr3(μ-CO)3(CO)8(η5-L) (M = W, Mo, L = C5H5; M = Mo, L = C5Me5) with the iridium capping reagents Ir(CO)2(η5-L′) (L′ = C5Me5, C5Me4H) in refluxing toluene afforded the trigonal-bipyramidal clusters MIr4(μ-CO)3(CO)7(η5-C5H5)(η5-L′) (M = Mo, L′ = C5Me5, 1a; M = W, L′ = C5Me5, 1b; M = Mo, L′ = C5Me4H, 1c; M = W, L′ = C5Me4H, 1d) and MoIr4(μ3-H)(μ-CO)2(μ-η1:η5-CH2C5Me4)(CO)7(η5-C5Me5) (2). Related reactions with M2Ir2(μ-CO)3(CO)7(η5-L)2 (M = W, Mo, L = C5H5; M = Mo, L = C5Me5) afforded M2Ir3(μ-CO)3(CO)6(η5-C5H5)2(η5-L′) (M = Mo, L′ = C5Me5, 3a; M = W, L′ = C5Me5, 3b; M = Mo, L′ = C5Me4H, 3c; M = W, L′ = C5Me4H, 3d), W2Ir3(μ-CO)4(CO)5(η5-C5H5)2(η5-C5Me4H) (4), and Mo2Ir3(μ-CO)3(CO)6(η5-C5Me5)3 (5). Single-crystal X-ray diffraction studies of 1a–1d, 2, 3a–3d, and 4 confirmed their molecular structures, including the μ-η1:η5-CH2C5Me4 ligand at hydrido cluster 2, derived from a C–H bond activation of one of the methyl groups. Density...