An Approach to Catalyst Design:  Cyclopentadienyl-Titanium Phosphinimide Complexes in Ethylene Polymerization

Abstract

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.

An investigation of catalyst/cocatalyst/support interactions in silica-supported olefin polymerization catalysts based on Cp*TiMe3*

“…In both of its methylene bridges between Ti and AlMe 2 , the methylene carbons are five-coordinate. The tris-tert-butylphosphinimide ligand resembles Cp* in its steric size and its electronic interaction with Ti [78]. Like the silica ligand, it can also bridge between Ti and Al.…”

Group 4 metal complexes for homogeneous olefin polymerisation: a short tutorial review

“…These attributes are evidence of a r?2p-bonding mode between ligand and metal just like Cp. The steric influence of the phosphinimides have also been shown to be comparable with Cp, and it is argued that the steric influence of the ligand is the most important factor in determining the polymerisation activity in these particular systems [65,67].…”

Transition Metal Imido Compounds as Ziegler–Natta Olefin Polymerisation Catalysts

“…Paul D. Bolton, Philip Mountford other highly active families, namely the ketimide system 6 [53] and the phosphinimide system 7, [54] both supported by cyclopentadienyl ligands. It is believed that in these systems the activity is enhanced by imido-type resonance contributions that increase the p-donor capability of the ligand.…”