Reaction of Polynuclear Acetylide Clusters. Synthesis of PentanuclearHeterometallic Clusters by Addition of [M(CO)₃(C≡CPh)(η-C₅H₅)] to [MOs₃(CO)₁₁(C≡CPh)(η-C₅H₅)] (M = Mo or W). Crystal Structures of [Mo₂Os₃(CO)₁₁(CCPhCCPh)(η-C₅H₅)₂]·2H₂O and [MoWOs₃(CO)₈(µ₄-C)-(µ₃-CPh)(CCPh)(η-C₅H₅)₂]·CH₂Cl₂

Both the cluster acetylide complexes [MOs₃(CO)₁₁(C≡CPh)(η-C₅H ₅)] [M = Mo, (1); or W, (2)] react with [Mo(CO)₃(C≡CPh)(η-C₅H₅)] to give in low yield planar pentanuclear complexes [MMoOs₃(CO)₁₁(CCPhCCPh)(η-C₅H ₅)₂] [M = Mo, (3); or W, (4)] which contain a C₄ hydrocarbon fragment derived from head-to-tail coupling between the two acetylide fragments. The C₄ chain of these complexes also undergoes twisting in solution, indicated by variable-temperature ¹H n.m.r. studies. Reaction of complex (1) with [W(CO)₃(C≡CPh)(η-C₅H₅)] does not produce the coupling product but induces C-C bond scission of [W(CO)₃(C≡CPh)(η-C₅H₅)] giving a novel carbide-alkylidyne complex [MoWOs₃(CO)₈(μ₄-C)(μ₃-CPh)(CCPh)(η-C₅H₅)₂] (5) in low yield. The structures of complexes (3) and (5) have been determined by single-crystal X-ray diffraction studies. Crystal data for (3): space group P2₁/n, a = 9.583(3), b = 25.175(10), c = 16.300(7) Å, β = 91.26(3)°, Z = 4, R = 0.051, and R′ = 0.053. Crystal data for (5): space group P1‾, a = 10.072(6), b = 13.217(3), c = 14.800(3) Å, α = 95.41(2), β = 93.17(4), γ = 109.14(4)°, Z = 2, R = 0.056, and R′= 0.062.