Hydrogen atom transfer in the oxidation of hydrogen peroxide by bis(bipyridine)oxo(pyridine)ruthenium(2+) and by bis(bipyridine)hydroxo(pyridine)ruthenium(2+)

The oxidations of H/sub 2/O/sub 2/ and of HO/sub 2//sup -/ by ((bpy)/sub 2/(py)Ru/sup III/(OH))/sup 2 +/ have been studied in aqueous solution. Rate constants and activation parameters for the oxidation of H/sub 2/O/sub 2/ by Ru/sup IV/ double bond O/sup 2 +/ are k(25/sup 0/C) = 1.74 +/- 0.18, ..delta..H/sup double dagger/ = 6.0 +/- 0.3 kcal/mol, and ..delta..S/sup double dagger/ = -37 +/- 3 eu and by Ru/sup III/-OH/sup 2 +/ are k(25/sup 0/C) = (8.09 +/- 0.27) x 10/sup -2/, ..delta..H/sup double dagger/ = 12 +/- 2 kcal/mol, and ..delta..S/sup double dagger = -38 +/- 3 eu. H/sub 2/O/D/sup 2/O kinetic isotope ratios are, for Ru/sup IV /double bond O/sup 2 +/, (k/sub H/sub 2/O/ /sup 250/C/k/sub D/sub 2/O /sup 250/C) = 22.0 +/- 1.2 and, for Ru/sup III/double bond OH/sup 2 +/, (k/sub H/sub 2/O /sup 250/C)/k/sub D/sup 2/O/ /sup 250/C) = 16.2 +/- 0.7. From rapid-mixing experiments ((bpy)/sub 2/(py)Ru/sup III/(OH))/sup +/ is the initial product of the oxidation of H/sub 2/O/sub 2/ by Ru/sup IV/ double bond O/sup 2 +/ rather than ((bpy)/sub 2/(py)Ru/sup II/(OH/sub 2/))/sup 2 +/, and it is proposed that oxidation of H/sub 2/O/sub 2/ by both Ru/sup IV/double bond O/sup 2more » +/ and Ru/sup III/ single bond OH/sup 2 +/ occurs by H atom (1e-1 H/sup +/) transfer. 38 references, 5 figures, 4 tables.« less