Polymerization and Isomerization of Olefins using Late-Transition Metal Complexes
Late-transition metal complexes serve as efficient olefin polymerization catalysts. The mechanism of α-diimine-palladium and nickel catalyzed olefin polymerization is well understood. By understanding the fundamental steps of olefin polymerization, catalysts can be rationally designed to achieve a polymer with desired properties. This dissertation focuses on understanding these fundamental steps in order to design complexes that serve as olefin polymerization and isomerization catalysts. Sandwich-diimine palladium catalysts were used to selectively isomerize 1-olefins to 2-olefins. By activating the palladium catalyst with phenylsilane and NaBArF, a broad range of olefins were isomerized at low catalyst loadings and low temperatures. Mechanistic studies show that regioselectivity is determined by selective displacement of bound internal olefin by a terminal olefin from palladium. Phenanthroline based palladium catalysts were shown to catalyzed a chain running isomerization of olefins. By changing the steric properties of the ligand, but using similar reaction conditions, an alternate, thermodynamic regioselectivity was obtained. A wide range of substrates were isomerized to produce synthetically useful products. The reaction is scalable with very low catalyst loadings. A new monodentate phosphine nickel complex was synthesized and shown to be an efficient olefin polymerization catalyst. The catalyst produced ultrahigh-molecular weight polyethylene and had a turnover frequency that is equivalent to the most active late-transition metal olefin polymerization catalysts. However, a short lifetime was observed and polymerization must be performed at room temperature or below.
Organometallic chemistry, Polymer Chemistry, Organic chemistry, Olefin Isomerization, Ultrahigh-molecular weight polyethylene
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