The objective of this project in the Inorganic, Bioinorganic and Organometallic Chemistry Program is to discover new ways to use transition metals as templates for the formation of chemical bonds. Such research is important in the design of catalysts for chemical synthesis and in modelling the action of metalloenzymes. The focus of the project is on reductive coupling, oxidative coupling and enantiospecific C-C bond formation (e.g., catalytic conjugate addition) between closely positioned ligands in transition metal complexes. High coordinate early transition metal complexes with linear ligands (CO, CNR, -CCR, etc.) provide a reaction channel for reductive coupling chemistry. Oxidative coupling will be explored using the polymetallic scaffold provided by fusing two oxo-centered triangular metal aggregates (M3O, M=Fe, Mn, Cr, Ru) or two di(mu2)dioxomanganese units, the latter affording a new approach to modelling the tetramanganese center in the dioxygen evolving complex of photosystem II. New catalytic and stoichiometric C-C bond forming reactions will be carried out between ligands bonded to two identical or disparate metal centers held at the poles of symmetric (containing two pairs of nitrogen donors) or asymmetric (e.g., containing a pair of phosphine donors and a set of three nitrogen donors) binucleating macrocycles. The results of these studies will afford insights into how high coordinate and polymetallic transition metal centers promote bond forming reactions in organometallic and bioinorganic chemistry and should lead to new molecules of fundamental interest as well as synthetic utility.
