Alumina-supported Mn(II) complexes with ligands of acetylacetonato (acac), N.N'-ethylenebis(salicylideneiminato) (salen), ethylenediamine (en) and 2,2'-bipyridine (bpy) catalyze the oxidation of cyclohexene with tert-butylhydroperoxide (TBHP) and hydrogen peroxide. Oxidation of cyclohexene with TBHP gave 2-cyclohexene-1-ol, 2-cyclohexene-1-one and 1-(tert-butylperoxy)-2-cyclohexene whereas, oxidation with H2O2 resulted in the formation of cyclohexeneoxide and cyclohexene-1,2-diol. Mn(IT) catalysts with the nitrogen donor ligands show significantly higher catalytic activity than oxygen donor ligands at the same surface coverage. The mechanism of oxidation has also been discussed. (C) 2002 Published by Elsevier Science B.V.