Titanium and zirconium complexes of chelating N-heterocyclic carbenes as polymerization catalysts

Abstract

We report the synthesis of novel titanium and zirconium complexes ligated by bidentate "salicylaldimine-like" Nheterocyclic carbenes (NHC). Double addn. of the NHC chelate to either TiCl_4(thf)_2 or ZrCl_4 forms bis-ligated organometallic fragments 1 and 2 with a distorted octahedral geometry. These complexes are rare examples of group IV transition metal NHC adducts. Preliminary catalytic tests demonstrate that in the presence of methylaluminoxane (MAO). These complexes are useful initiators for the polymn. of ethylene and the copolymn. of ethylene with norbornene and 1-octene. It has been obsd. that the polyethylene produced is linear high d. polyethylene. The Ti complexes were also employed to produce highly syndiotactic polystyrene. Non- Metallocene Ti and Zr Precatalysts.

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