Theory for Control of Selectivities in Reactions and Visualization of Organometallic Reactions

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We have studied the following subjects.1. The high reactivity of silicon compounds has been studied theoretically. The mechanism of ligand substitution reactions of pentacoordinated silicon species with H^- and with F^- has been clarified by means of ab initio MO calculations. The selectivity in the reaction has been discussed by locating hexacoordinated transition states on the potential energy surfaces. The difference in reactivities and chemical bondings between silicon compounds and carbon compounds has been clarified by means of orbital interactions.2. The interaction between transition metals and carbon cluster C_<60> has been investigated by applying paired orbital interaction scheme. The interaction has been shown to be very local, bearing a close resemblance to the transition-metal complexes of alkenes.3. The effect of triethylamine on the telluroxide elimination has been investigated experimentally and its mechanism has been suggested.4. Asymmetric epoxidation by Sharpless reagent has been studied theoretically.5. Theoretical calculations on selenoxide elimination have clarified the origin of selectivities in the reaction.6. A new orbital concept has been derived on the basis of electron delocalization. Multifariousness and likeness of chemical reactions have been shown to be connected with the frontier orbital theory. Novel concepts of local electronegativity and hardness have been proposed.