Zirconocene complexes of the sterically demanding pentaphenylcyclopentadienyl ligand, Cp-PRO. Synthesis and characterization of (CpZrCl3)-Zr-PRO and (CpCpZrCl2)-Zr-PRO (Cp = eta(5)-C5H5; Cp-PRO = eta(5)-C-5(C6H5)(5))

The synthesis, characterization and X-ray structures of two zirconium compl exes of the bulky pentaphenylcyclopentadienyl ligand, C-P(PRO), are reporte d. The monocyclopentadienyl 12 electron complex, (CPZrCl3)-Zr-PRO (I), has an unusual monomeric structure in the solid state and has short Zr-ligand d istances. The Lewis acidity of this complex is manifested in its ability to catalyze the [4 + 2] cycloadditions of methyl- and ethylmethacrylate to cy clopentadiene. The sandwich complex, (CPCpZrCl2)-Cp-PRO (II), has more typi cal Zr-ligand distances, but has a more parallel arrangement of the two cyc lopentadienyl rings. (C) 1999 Elsevier Science S.A. All rights reserved.