COMP 101 |
| The mechanism for the reaction of molecular oxygen with toluene-solvated palladium-hydride complex has been elucidated using quantum mechanics (B3LYP/ LACVP** with PBF polarizable continuum solvent model) for PdII-((-)sparteine)(H)(Cl) in the presence of base, focusing on the pathways proceeding through Pd0 as well as direct insertion of O2 into the Pd-H bond. The lowest barrier Pd0 pathway proceeds through a rate-determining base-assisted deprotonation of the palladium, followed by the association of molecular oxygen and the subsequent loss of chloride, forming the corresponding η2-peroxo-palladium complex, while the lowest insertion pathway proceeds through the abstraction of the hydrogen atom by triplet O2 followed by the formation of a L2XPdIOOH triplet species and eventually the loss of H2O2 and completion of the catalytic cycle upon the addition of HX. Examination of the spin-transitions as well as the completion of the reaction to form PdCl2 and H2O2 are included. These results form the first complete mapping of the possible pathways for reoxidation of palladium hydride with molecular oxygen. For this particular system, we conclude that direct insertion is preferred (ΔΔH‡ = 6.2 kcal/mol, ΔΔG‡ = 7.7 kcal/mol), and trace this preference to the bidentate character of sparteine and the lack of π-accepting ligands. Suggestions are included for how this preference can be switched. |
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Bold Predictions in Theoretical Chemistry: A Poster Session in Honor of One of the Boldest, Bill Goddard, on the Occasion of his 70th Birthday
7:30 PM-9:30 PM, Sunday, August 19, 2007 BCEC -- Exhibit Hall - B2, Poster
Division of Computers in Chemistry |