Cyclopentadienone and Hydroxycyclopentadienyl Cobalt Complexes from the Reaction of an Alkynylphenylsilane with Co2(CO)8

Reaction of dimethyl(pent-1-yn-1-yl)phenylsilane n-PrCCSiMe2Ph (1) with Co2(CO)8 in n-heptane or 1,4-dioxane led to the formation of cobalt complexes with carbon–carbon bond coupling and insertion of a carbonyl ligand ([2 + 2 + 1] cycloaddition). In both solvents, the compounds (n-PrCCSiMe2Ph)·Co2(CO)6 (2), {[n-Pr2(PhMe2Si)2C4CO]Co(CO)2}2 (3), and [n-Pr2(PhMe2Si)2C5OH]Co(CO)2 (4) were obtained. In n-heptane, a fourth cobalt complex (5) was isolated as well but could not be identified, while in 1,4-dioxane, metallic cobalt formed instead. The yields of 3 and 4 in 1,4-dioxane were distinctly higher than those in n-heptane (11 and 21% vs 7.5 and 6%). All compounds were characterized by spectroscopic methods (NMR, IR, UV/vis), and the molecular structures of 3 and 4 were determined.