The reaction of π-cyclopentadienyldicarbonylcobalt with silyl-substituted acetylenes

The reaction of (π-C₅H₅)Co(CO)₂ with PhCCSiMe₂R (R = Me, SiMe₃) gave two isomeric cyclobutadiene complexes, cis- and trans-(π-C₅H₅)CoPh₂C₄(SiMe₂R)₂], in almost quantitative yields. However, the reaction with RMe₂SiCCSiMe₂R (R = Me, Ph) led to the formation of new dinuclear cobalt complexes. For example, with bis(trimethylsilyl)acetylene, (π-C₅H₅)₂Co(CO)(Me₃Si)₂C₂] was obtained quantitatively. The latter was further converted to (π-C₅H₅)Co(Ph₄C₄) and (πC₅H₅)Cocis-Ph₂C₄(Me₃Si)₂] by treatment with PhCCPh. The physical properties and spectroscopic characteristics of these new compounds are described.