Titanium and zirconium complexes that contain a tridentate bis(phenolato) ligand of the [OOO]-type

Abstract

The oxygen-linked bis(phenol) 2-oxapropanediyl-1,3-bis(2- tert-butyl-4-methylphenol), [OOO]H 2, was prepared in good yield by the condensation of 2- tert-butyl-6-hydroxymethyl-4-methylphenol at 155 °C. This bis(phenol) reacted cleanly with titanium tetrachloride to give the orange titanium dichloro complex [OOO]TiCl 2 in virtually quantitative yield. The solubility in pentane indicates a monomeric structure for [OOO]TiCl 2 in solution. The reaction of titanium tetra(isopropoxide) gave the di(isopropoxy) complex [OOO]Ti(O iPr) 2 which also adopts a monomeric structure of C 2 v -symmetry in solution. The reaction of the dichloro complex [OOO]TiCl 2 with benzyl Grignard reagent in diethyl ether gave the highly light- and air-sensitive, orange dibenzyl complex [OOO]Ti(CH 2Ph) 2 in good yield. Single crystal X-ray crystallography revealed a penta-coordinate titanium center coordinated to two monohapto benzyl ligands and the tridentate [OOO] ligand in a meridional fashion. The reaction of zirconium tetrabenzyl with [OOO]H 2 gave the bis(ligand) complex [OOO] 2Zr, regardless of the stoichiometry employed. Crystallographic analysis shows an octahedral coordination geometry with cis-configuration of the two ligands. The compound can be transformed into the dichloro complex [OOO]ZrCl 2 by disproportionation with zirconium tetrachloride. Polymerization tests using [OOO]TiCl 2 under methylaluminoxane activation revealed moderate polymerization activity towards ethylene and styrene.