Simple soluble Bi(III) salts as efficient catalysts for the oxidation of alkanes with H2O2

A simple catalytic system based on a soluble bismuth(III) salt, Bi(NO3)(3)/H2O2/HNO3/CH3CN + H2O, exhibits pronounced activity towards the homogeneous oxidation of inert alkanes with the yield of oxygenate products up to 32% and TON up to 112. The experimental selectivity parameters and kinetic data together with theoretical DFT calculations indicate that the reaction occurs via a free radical mechanism involving the formation of the HO center dot radicals which directly react with alkane molecules. The mechanism of the HO center dot generation (which is the rate limiting step of the whole process) includes the substitution of a water ligand for H2O2 in the initial aqua complex[Bi(H2O)(8)](3+), hydrolysis of the coordinated H2O2, second H2O-for-H2O2 substitution and the homolytic HO-OH bond cleavage in complex[Bi(H2O)(4)(H2O2)(OOH)](2+) (6). The relatively low overall activation energy for this process (ca. 20 kcal mol(-1)) is accounted for by the high lability and acidity of the Bi aqua complexes and tremendous activation of coordinated H2O2 in 6 towards homolysis.