Zwitterionic 18-electron d(0)-anionic metallocene complexes

Formal [3+2] cycloaddition reactions between the alpha-phosphino zirconaind ene 1 and various cumulenes [CO2, CS2, Cy-N=C=N-Cy (Cy = cyclohexyl), R-N=C =S (R = Me, Ph), R-N= C=O (R = Ph, Bu-t)] afford stable zwitterionic monome ric five-coordinated anionic bis(cyclopentadienyl) zirconium complexes 2-6. Single-crystal X-ray structures of two of these compounds (3, 6b) are repo rted. A related biszwitterionic zirconocene complex 9 is prepared through t he reaction of carbon disulfide with the tricyclic alpha-phospholane zircon aindan 7; in this case cycloaddition reactions take place on the two carbon sulfur double bonds of CS2.