New carbene and vinylidene chelate complexes of cyclopentadienylcobalt bearing a phosphorus tether

The {eta (5)[2-(di-tert-butylphosphanyl-P)ethyl]cyclopentadienyl} cobalt ch elate was treated with trimethylsilylethyne to give the corresponding alkyn e complex along with the trimethylsilylvinylidene complex. In a similar way , the bis(trimethylsilyl)ethyne complex was obtained. Silyl migration to gi ve the bis(trimethylsilyl)vinylidene complex was observed at elevated tempe rature and represents the first cobalt example of this reaction. As the fir st cobalt vinylidene complex the bis(trimethylsilyl)vinylidene complex was characterized by an X-ray structure analysis. Reaction of the cobalt chelat e with an Arduengo type carbene unexpectedly gave a non-chelated cobalt com plex bearing the carbene ligand and ethene at the same metal atom. This com plex was also structurally characterized. (C) 2001 Elsevier Science B.V. Al l rights reserved.