Synthesis and X-ray Structural Characterization of Oxygen Bridged Complexes for Olefin Polymerization: A Theoretical Interpretation of Structure and Activity Relationship

Abstract

This PhD thesis describes the synthesis and X-ray structural studies of oxygen bridged heterobi- and trimetallic complexes for olefin polymerization reactions. First part of work describes the preparation and characterization of heterobi- and trimetallic complexes of group 4 metals. These compounds were used as catalysts for the ethylene and styrene polymerization reactions. The compounds exhibit high catalytic activity in the polymerization reactions. The complex Cp*2MeZr(µ-O)TiMe2Cp* produces the linear low density polyethylene (LLDPE). The role of bridged-oxygen in the complexes was studied by the means of DFT calculation studies. The oxygen plays very important role in enhancing the Lewis acidity at the metal centers and consequently decreases consumption of co-catalysts (such as MAO). The second part of this work demonstrates that it is possible to isolate highly unstable and photosensitive mono and biscyclopentadienyl complexes bearing methyl groups as bimetallic complexes using LMeAl(OH). Series of monocyclopentadienyl based heterobimetallic complexes containing Al(µ-O)M (M = Ti, Zr) were prepared and were used as catalysts in the olefin polymerization reactions. The complexes exhibit high activity in the olefin polymerization. The last part of this thesis describes the synthesis of heterotrimetallic complexes containing Al(µ-O)M(µ-O)Al. The complexes exhibit low activity in the polymerization reactions which may be due to formation of less stable cation during the polymerization reactions. The last chapter describes the synthesis and X-ray structural analysis of lithiated salt of Cp2Ti(SH)2.