MECHANISM OF C-H BOND OXIDATION BY A MONOOXORUTHENIUM(V) COMPLEX

The complex [Ru(v)L(O)]2+ {HL = [2-hydroxy-2-(2-pyridyl)ethyl]bis[2-(2-pyridyl)ethyl]amine} was found to be a very active stoichiometric oxidant towards various hydrocarbons. Oxidation of alcohols was studied either in 0.1 mol dm-3 HClO4 or CH3CN, the observed rate law being rate = k[Ru(v)][alcohol]. The second-order rate constants for various alcohols follow the order benzylic > secondary > primary alcohols. Kinetic isotope effects (k(H)/k(D)) of 5.9 and 5.3 were found for benzyl alcohol and Pr1OH respectively. Similar kinetic studies for the oxidation of tetrahydrofuran gave k(H)/k(D) = 6.8. Stoichiometric oxidation of saturated alkanes in acetonitrile gave tertiary alcohols exclusively or ketones when only methylene groups are present. The measured k(H)/k(D) for the oxidation of cyclohexane determined from competitive oxidation experiments was 5.3. No cyclohexyl chloride was found when the oxidation of cyclohexane was carried out in the presence of CCl4. The mechanism of C-H bond oxidation by Ru(v) = O is discussed.