Synthesis and reactivity of tantalocene zwitterions stabilized by ground-state alpha-agostic interactions via reaction of B(C6F5)(3) with Cp ' Ta-2(=CH2)(CH3) (Cp ' = C5H5, C5H4Me)

Zwitterionic tantalocene derivatives are formed when the perfluorophenyl-su bstituted borane B(C6F5)(3) is reacted with the tantalocene methyl methylid ene complexes Cp'Ta-2(=CH2)(CH3) (Cp' = C5H5, C5H4Me). The products arise f rom borane attack of the methylidene ligand and are characterized by a stro ng, ground-state alpha-agostic interaction, and insertion. of tert-butyl is ocyanide occurs exclusively into the agostic Ta-C bond, producing iminoacyl zwitterions.