On the Reaction of C(PPh3)2 with [Co2(CO)8]: Formation and Structure of an Unusual Tetranuclear Cluster

The reaction of the carbodiphosphorane C(PPh3)2 (1) with [Co2(CO)8] results in the formation of the salt-like complex (HC{PPh3}2)[Co(CO)4] (2) in high yield if THF is used as the solvent. The proton of the cation stems from THF degradation. When the reaction is carried out in toluene, the tetranuclear cluster [Co4(CO)10(PPh3)(μ4-CCPPh3)] (3) is formed in low yield as the only complex which could be identified by X-ray analysis. The solvate 3 ·C7H8 crystallizes in the triclinic space group P1̄ with a = 1040.8(2), b = 1387.4(2), c = 1923.0(2) pm, α = 71.96(1)◦, β = 88.69(1)◦, γ = 71.46(1)◦, Z = 2. The structure of the cluster with 64 CVE is that of a “spiked triangle” in which the triphenylphosphonioacetylide CCPPh3 acts as a six-electron donor and the bonding mode is that of a μ4-η coordination.