Oxygenation of saturated and aromatic hydrocarbons with H2O2 catalysed by the carbonyl thiophenolate iron complex (OC)3Fe(PhS)2Fe(CO)3
•An iron-thiophenolate organometallic complex catalyses efficient oxidations with H2O2.•Alkanes are oxidized to alkyl hydroperoxides and benzene to phenol in mild conditions.•Pyrazinic acid and pyridine are promoters and TONS up to 2300 are achieved.•Kinetics and selectivity studies indicate the participation of hydroxyl radicals.
The compound (OC)3Fe(μ-PhS)2Fe(CO)3 (1) containing a [Fe2S2] diiron moiety catalyses the oxygenation of alkanes and benzene with hydrogen peroxide in air, in acetonitrile solution. Alkyl hydroperoxides are formed as the main reaction products in the alkane oxidation; benzene is transformed into phenol. Addition of pyrazine-2-carboxylic acid (PCA) improves the oxidation. Some lag period can be noticed. If pyridine is simultaneously introduced into this reaction mixture the oxidation rate increases and the duration of the lag period is substantially decreased and in some cases this period can be completely removed. Turnover numbers attain 2300. It is noteworthy that addition of picolinic acid instead of PCA leads to the complete oxidation inhibition. The oxidation proceeds non-stereoselectively and bond selectivity parameters are low, what testifies the participation of hydroxyl radicals in hydrocarbon functionalization. Radical HO attacks the hydrocarbon, RH, to generate alkyl radical, R, which very rapidly reacts with molecular oxygen.
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Journal: Catalysis Today - Volumes 218–219, December 2013, Pages 93–98