The dinuclear manganese(IV) complex [LMn(O)(3)MnL](PF6)(2) (1, L = 1,4,7-trimethyl-1,4,7-triazacyclononane) catalyzes the extremely efficient oxidation of alcohols with hydrogen peroxide at room temperature. Oxalic acid is an obligatory co-catalyst. The oxidation of isopropanol, for example, yields acetone with turnover numbers up to 40000 after 5-10 h in the absence of a solvent. 2-Cyanoethanol was oxidized by this system with somewhat lower efficiency (conversion 70%). The catalytically active cation from salt 1 was obtained in an insoluble form containing a heteropoly anion [Mn2O3(TMTACN)(2)](2)[SiW12O40]. Oxidation of 2-cyanoethanol using this heterogenizedcatalyst and oxalic acid gave the oxo-products with the 54% total yield.