Saafani, Mohammed Ali Yahya Al

English

Open Access Repository of Indian Theses

Abstract of the thesis entitled “Synthesis, characterization and olefin polymerization reactivity of some early and late transition metal complexes” This thesis describes the synthesis and characterization of selected early and late transition metal complexes and their usefulness as catalysts for the polymerization of ethylene.Polymerization of ethylene was studied using copper(II) complexes based on -diimine, bis(oxazoline) and bis(benzimidazole) ligands. (-diimine) copper(II) complexes bearing an acenapthene ligand framework exhibited moderate activity for polymerization of ethylene when activated with MAO at 5 bar ethylene pressure and maximum activity was observed for the complex with ortho-isopropyl substituents.  The complex bearing an aliphatic -diimine ligand framework was inactive for polymerization of ethylene even at 5 bar pressure indicating that nature of the chelating ligand plays an important role in the generation and stabilization of the active species.  Poly(ethylene)s produced by the copper complexes were linear and exhibited high molecular weights and narrow molecular weight distributions which implies the single site nature of the active species. The active species is proposed to be a copper(II) centre with -Cl or -Me bridges.  Bis(oxazoline) and bis(benzimidazole) copper(II) complexes were not active for polymerization even at 5 bar pressure.Group 4 (Ti, Zr, Hf) metal complexes of trans-2-[9-(H) fluorenyl] cyclohexanol were studied for the polymerization of ethylene with MAO as cocatalyst.  They exhibited moderate catalyst activity for polymerization of ethylene and activity decreased in the order Zr>Ti>Hf.  These complexes exhibited activity even at 100C.  The zirconium complex produced poly(ethylene)s with exclusively saturated chain ends when the polymerization was conducted at 25-60C.  The saturated chain ends may result from chain transfer to aluminium.  However, at temperatures above 80C, a mixture of solid polymer and soluble oligomers was obtained.   The solid polymer consisted of long chain branches that are proposed to be formed by -H transfer followed by reincorporation of the resulting macromonomers into the growing polymer chains.  When the polymerization was conducted at 100C, methyl branches were also observed in the polymer in addition to long chain branches.  These methyl branches may result from -H transfer followed by 2,1-insertion of the -olefin into the [Zr-H] species. Both saturated chain ends and vinyl unsaturation were observed in poly(ethylene)s produced at higher temperatures that implies that -H transfer becomes more competitive with chain transfer to aluminium.  The soluble oligomers produced at higher temperatures were found to consist of a mixture of linear -olefins and long chain alkanes.  Half sandwich fluorenyl amido complexes of titanium and zirconium based on ligands bearing aromatic substituents on the amido nitrogen were synthesized and employed as catalysts for the polymerization of ethylene with MAO as the activator.  The complexes exhibited moderate catalyst activity and resulted in linear, high molecular weight poly(ethylene)s.  Catalyst activities of these complexes were lower when compared to similar complexes bearing alkyl substituents on the amido nitrogen. It is speculated that resonance effect of the aromatic substituents may be responsible for the lower catalyst activities.A.Rajesh								Dr.S.Sivaram(Research scholar)							(Research supervisor)Date:

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