Remarkably Active Non-Metallocene Ethylene Polymerization Catalysts

Abstract

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.