Investigations of Metal-Element Multiple Bonding and New Methods for Metal-Mediated Bond Activations

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Professor T. Don Tilley, Department of Chemistry, University of California at Berkeley is supported by the Inorganic, Bioinorganic, and Organometallic Chemistry Program of the Chemistry Division to investigate complexes that contain a transition metal-main group element multiple bond and to develop new methods for transition metal mediated bond activations. A primary reaction type by which transition metal centers cleave chemical bonds involves the migration of a group from a donor atom to the metal (alpha - migration). This process produces a metal-element multiple bond, which is a functionality with a rich reaction chemistry and which is important in many metal-mediated transformations. Although alpha-migrations are well established for metal-carbon bonded systems, they are much less developed in M-N, M-O, M-Si, M-P, and other metal heteroatom systems. This proposal aims to assess the generality and synthetic utility of alpha-migration as a route to isolable species containing multiple bonds between various main group and transition metal fragments. In doing so, several fundamental questions will be addressed: (a) Can alpha-migration be used to generate new types of metal-element multiple bonds? (b) How does the electron count at the transition metal center influence alpha-migration chemistry? (c) Does a formally charged metal center promote the alpha-migration process? (d) What substituents in addition to hydrogen participate in alpha-migration chemistry? (e) Can the design and implementation of new ligand sets provide access to new bond activations? (f) Can alpha-migrations be incorporated into new catalytic cycles? To address these questions, specially designed complexes containing metals from throughout the transition series will be prepared. Many of these will feature coordinative unsaturation, and ligands designed to facilitate bond activations.The goal of this work is to provide a basis for the development of new and useful metal-mediated chemical processes. The discovery of new bonding patterns and reactivity modes will be followed by attempts to use this information in the design of new catalytic cycles. Many of these investigations will focus on silylene complexes that have recently been discovered, but as other metal-element multiple bonded compounds are obtained, their reactivities will be explored in the search for useful transformations.