Synthesis and catalytic activity of camphor titanium complexes

Abstract

Three new camphor–titanium complexes [TiClCp2L] (L=1L, (1); 2L, (2) and 3LH (3)) were obtained through replacement of one chloride by a camphor-type ligand (1LH, 2LH, 3LH2 (3)) at the coordination sphere of [TiCl2Cp2]. Complexes 1 and 2 were structurally characterized by X-ray diffraction analysis showing that coordination occurs through the oxygen atom of the hydroxo group (1) with cooperative coordination of the nitrogen atom of the oxime complex in 2. Upon activation with MAO complexes 1 and 2 promote ethylene polymerization and ethylene/norbornene co-polymerization while compound 3 displays no catalytic activity for either one or the other process. At 50°C the catalytic activity complex of 2 (852kgPEmol−1h−1) for ethylene polymerization is higher than that of compound 1 (668kgPEmol−1h−1) which is similar to that of [TiCl2Cp2] (670kgPEmol−1h−1). The catalytic activity of complex 1 displays a higher dependence on the temperature than that of compound 2 which is attributed to the strength of the Ti–O bond that renders generation of the active site more difficult in 1. Compounds 1 and 2 are also active catalysts for co-polymerization of ethylene with norbornene affording copolymers with approximately 15mol% of norbornene content.The microstructures of the polyethylenes and ethylene norbornene co-polymers were checked by NMR and their melting points were measured by DSC.