Titanium Complexes Having Chelating Diaryloxo Ligands Bridged by Tellurium and Their Catalytic Behavior in the Polymerization of Ethylene

A series of titanium complexes having tellurium-bridged chelating bis(aryloxo) ligands, [TiX 2 {2,2‘-Te(4-R-6-R‘-C 6 H 2 O) 2 }] 2 ( 5b, X = Cl, R = Me, R‘ = t Bu; 6a, X = O i Pr, R = R‘ = H; 6b, X = O i Pr, R = Me, R‘ = t Bu), were prepared. 5b and 6b were determined by X-ray crystallography to have chloro- and isopropoxo-bridged dimeric structures. The structural data for these complexes indicated that the Ti−Te coordination bonds were stronger than the similar Ti−S coordination bonds in the corresponding sulfur-bridged complexes. The reaction of (C 5 R 5 )TiCl 3 (R = H, Me) with 2,2‘-Te(4-R-6-R‘-C 6 H 2 OLi) 2 gave monocyclopentadienyl derivatives, (C 5 R 5 )TiCl{2,2‘-Te(4-Me-6- t Bu-C 6 H 2 O) 2 } ( 7, R = H; 8, R = Me). The monomeric four-legged piano-stool geometry of 8 was revealed by X-ray analysis. Upon addition of methylaluminoxane (MAO), these complexes catalyzed the polymerization of ethylene. The activities of the tellurium-bridged complexes were found to be significantly higher than those of the corresponding methylene-bridged complex.