New O-and N-bonded zirconocene complexes and their catalytic properties in ethylene polymerization. X-ray crystal structure of (C5H5)2Zr[2,6-OC6H3(CH3)2]2, (C5H5)2Zr[2,4,6-OC6H2(CH3)3]2 and (C5H5)2Zr(CH3)[CH(NC6H5)2]

A series of zirconocene complexes of formula Cp2ZrMe2nLn where CpC5H5 , Memethyl, Lpyrazolyl, bis(N,N%- phenylformamidinato), or substituted aryloxide and n1,2, were synthesized by reaction of Cp2ZrCl2 and Cp2ZrMe2 with LiL or HL, respectively. The structures of Cp2Zr(2,6-OC6H3Me2)2, Cp2 Zr(2,4,6-OC6H2Me3)2 and Cp2ZrMe{CH(NC6H5)2} were determined by single crystal X-ray diffraction. The complexes demonstrate appreciable activity for ethylene polymerization when used as cocatalysts with methylaluminoxane and dimethylanilinium tetrafluorophenylborate