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Enantioselective hydrosilylation by chiral Pd based homogeneous catalysts with first-principles and combined QM/MM molecular dynamics simulations

A review of the enantioselective hydrosilylation of styrene catalyzed by Pd0 species generated in situ from dichloro{1-{(R)-1-[(S)2(diphenylphosphino kP)ferrocenyl]ethyl}-3-trimethylphenyl-5-1H-pyrazole-kN}palladium, 1, was studied in detail by ab initio mol. dynamics and combined quantum mechanics and mol. mechanics (QM/MM) simulations. The nature of the unique structural features obsd. in the pre-catalyst, 1, and its bis(trichlorosilyl) derivs. were explored. Using the combined QM/MM method the authors were able to pinpoint the steric and electronic influence of specific ligands on these geometric distortions. The whole catalytic cycle of the enantioselective styrene hydrosilylation was examd. in detail with mixed QM/MM Car-Parrinello mol. dynamics simulations. The simulations show that the reaction proceeds through the classical Chalk-Harrod mechanism of hydrosilylation. The rate-detg. step is the migration of the silyl ligand to the a-C of the substrate. The nature of the regiospecificity and enantioselectivity of the catalysis was established. In both cases the formation of a h3-benzyllic intermediate plays a crucial role. The mechanistic detail afforded by the computational study provides a framework for rational ligand design that would improve the enantioselectivity of the catalysis. [on SciFinder (R)]

    Reference

    • LCBC-CHAPTER-2002-010

    Record created on 2006-02-27, modified on 2016-08-08

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