Theoretical Studies of Structure and Reactions of Transition Metal Atoms, Ions, Complexes and Clusters

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Keiji Morukuma of Emory University is supported by the Theoretical and Computational Chemistry Program to study the structure and reactions of transition metal clusters and complexes using ab initio, density functional, and ONIOM (hybrid molecular orbital plus molecular orbital or molecular mechanics) methods. The ONIOM method, which allows inclusion of complex real ligands into computations, will be developed and calibrated for large transition metal complexes. As well, the ONIOM-PCM (polarized continuum model) method will be tested and employed to study organometallic reactions in solutions. Close contact with experimental chemists will be maintained, while experimentally relevant problems are explored. Gas phase reactions of dihydrogen, alkynes, and alkenes with bare transition metal clusters and C-C, C-H and molecular nitrogen bond activation, along with skeletal rearrangement, on trinuclear ruthenium complexes will be studied, with the goal of examining metal clusters that can catalyze reactions not possible on a single transition metal center. As well, the mechanisms of several important reactions in organometallic chemistry will be elucidated, encompassing a wide variety of reactions of mononuclear transition metal complexes and full homogeneous catalytic cycles including (a) olefin copolymerization, (b) element-element addition to unsaturated hydrocarbons, (c) utilization of metal-ligand multiple bonds, (d) transition metal catalyzed cycloisomerizations, (e) reaction of allylic compounds with formic acid or metal-hydride, and olefin metathesis. The knowledge of structure, spectroscopic properties, and energies of reaction intermediates and transition states that will be gained from this research is expected to promote fundamental understanding as well as aid logical design of new catalysts for better control of complicated chemical reactions. This computational research project complements efforts in experimental chemistry, and is expected to promote the fundamental understanding of complex chemical reactions. Although many industrial catalytic processes have been developed in the past, the chemical industry is trying hard to switch to catalysts using clean homogeneous processes. Designing efficient catalysts is one of the areas where computational chemistry can make a substantial impact in the chemical industry.