ETHYLENE POLYMERIZATION WITH HALF-SANDWICH ALLYL IMIDO COMPLEXES OF TANTALUM

The imido-based half-sandwich complex (2,6-diisopropylphenyl))(eta(1)- C3H5)(eta(3)-C3H5) (3) polymerizes ethylene in the presence of [(C6H5) (3)C](+)-[(C6F5)(4)B](-) or B(C6F5)(3), while chloride and alkyl deriv atives are inactive in. the presence of MAO or alkyl abstraction reage nts. In contrast, however, CpTa(=NSi(tert-butyl)(3))Cl-2 (5) polymeri zes ethylene in the presence of MAO while Ta(=NSi(tert-butyl)(3))(eta (1)-C3H5)(eta(3)-C3H5) (6) and CpTa(=NSi(tert-butyl)(3))Me-2 (4) are essentially inactive in the presence of alkyl abstractors.