Organometallic Chemistry of Metallo Macrocycles

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The focus of this project are organometallic compounds in which the metals cobalt, rhodium or iridium are bound to macrocyclic ligands, i.e. organic molecules which provide several donor atoms for binding the metal and whose structures contain several rings. Such compounds show considerable promise for use in the reductive coupling of carbon monoxide, a process in which carbon monoxide is converted to more complicated and useful organic molecules. A series of organometallic reactions that achieve measurable equilibria will be used in deriving thermodynamic parameters for subsequent use in estimating M-H and M-C bond energies. Variation of the reaction environment by solvent effects, zeolite encapsulation and addition of Lewis acids and bases will be exploited as a means of altering reaction thermodynamics and kinetics in order to promote new organometallic reactivity. Rhodium and iridium porphyrin species have an extraordinary breadth of organometallic reactivity, which encompasses the areas of C-H bond activation, alkene coordination and oxidation, formation of heterobimetallic complexes, reductive coupling of carbon monoxide, and the formation of species with carbene, formyl or hydroxymethyl species bound to the metal. A major effort will be made to discover non-porphyrinic macrocycles and chelate ligand systems which emulate metalloporphyrin reactivity, but which have improved reaction rate characteristics.