Complexes of the form (Cp†)TiCl2(NPR3) and the analogous dimethyl derivatives (Cp†)TiMe2(NPR3) have been prepared. These species in the presence of MAO, B(C6F5)3, or [Ph3C][B(C6F5)4] are active catalysts for ethylene polymerization.

The bis(tri-tert-butylphosphinimide) complexes (t-Bu3PN)2TiCl2 (1) and (t-Bu3PN)2TiMe2 (2) were prepared and characterized crystallographically. Stoichiometric reactions of 2 with PhNMe2H[B(C6F5)4] in the presence of PMe3 afforded [(t-Bu3PN)2TiMe(PMe3)][B(C6F5)4] (3), while reaction of 2 with B(C6F5)3 affords (t-Bu3PN)2TiMe(μ-Me)B(C6F5)3 (4). Under laboratory conditions these compounds are effective ethylene polymerization catalysts. Under commercially relevant solution polymerization conditions, these catalysts are exceptionally active. Complex 2, when activated with Ph3C[B(C6F5)4], produces high molecular weight polyethylene with a narrow polydispersity at a rate approximately 4 times faster than the constrained geometry catalyst ((C5Me4SiMe2N-t-Bu)TiX2). As such, these catalysts represent the first non-cyclopentadienyl, single-site catalysts competitive with derivatives of metallocenes under commercially relevant polymerization conditions.

A strategy for polymerization catalyst design has been developed based on the steric and electronic analogy of bulky phosphinimides to cyclopentadienyl ligands. To this end, the family of complexes of the form (Cp†)TiCl2(NPR3) has been prepared and characterized. Alkyl and aryl derivatives of these species have also been synthesized, and a number have been evaluated for use as catalyst precursors in olefin polymerization. The polymerization of ethylene has been examined employing several types of cocatalyst activators. Trends and patterns in the structure−activity relationship are discussed, and the implications for catalyst design are evaluated.

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