Catalysis and Mechanistic Studies of Ru(III), Os(VIII), Pd(II), and Pt(IV) Metal Ions on Oxidative Conversion of Folic Acid

The homogeneous catalysis of Ru(III), Os(VIII), Pd(II), and Pt(IV) in the oxidative conversion of folic acid (FA) to pterin-6-carboxylic acid, p-aminobenzoic acid, and glutamic acid by sodium N-bromo-p-toluene-sulfonamide (bromamine-T; BAT) was studied in alkaline medium. The detailed kinetic and mechanistic investigations of all four catalyzed oxidation reactions were studied at 313 K. The stoichiometries and oxidation products of the four catalyzed reactions were found to be the same, but their kinetic patterns and oxidation mechanisms were different. The reactions were studied at different temperatures, and the activation parameters were evaluated for each catalyzed reaction. Under identical sets of experimental conditions, the kinetics of all four catalyzed reactions were compared with those of uncatalyzed reactions, revealing that the catalyzed reactions are 6-22 times faster. The catalytic efficiency of these catalysts follows the order Os(VIII) > Ru(III) > Pt(IV) > Pd(II). This trend can be attributed to the different d electronic configuration of the catalysts. Based on the observed experimental results, a detailed mechanistic interpretation and the related kinetic model were derived for each catalyst.