Organoboron Derivatives of Group 4 Metals

Regents Of The University Of Michigan - Ann Arbor, Ann Arbor MI

Investigators

Abstract

Dr. Arthur J. Ashe, III, Department of Chemistry, University of Michigan, is supported by the Inorganic, Bioinorganic, and Organometallic Program of the Chemistry Division for the study of heteroaromatic compounds involving group 13 and 15 elements, their use as ligands to form zirconium complexes, and the development of these complexes as olefin polymerization catalysts. Previous research has demonstrated that boratabenzene zirconium complexes can serve as homogeneous catalysts for the polymerization of olefins. Building on this result and by analogy to ansametallocenes that are known to be active catalysts, a series of metal complexes containing heteroaromatic ligands will be designed with the goal of obtaining highly active and stereospecific olefin polymerization catalysts. Specifically, new oxaborolides, thiaborolides and azaborolides will be synthesized. These compounds along with boratabenzenes, which are bridged through boron or carbon-(2), will be used as ligands to form Group 4 metal complexes, which will be evaluated as polymerization catalysts. Additionally, the conversion of aminoboranediyl bridged zirconocenes to highly active and stereoselective Ziegler-Natta catalysts will be studied. Transition metal complexes promote very selective catalytic and stoichiometric transformations of organic compounds. Much of the unique reactivity at the metal center is a reflection of the density of electrons surrounding the metal and this electron density can be controlled by adjusting the groups that are attached to the metal. A very common 'group' contains a ring of carbon-hydrogen units in what is called an 'aromatic' arrangement. In this project a series of metal complexes will be prepared in which an 'aromatic' group composed of carbon-hydrogen and boron species is attached to a metal. This will permit the electron density about the metal to be carefully adjusted in order to promote specific chemical and catalytic behavior and will set the ground work both to understand existing processes and to rationally design new catalysts.