The in-situ transition metal complexes of five ligands L1-L5 were reported and examined for their catecholase activities at ambient conditions, we found that reaction rate depends on five parameters: Nature of the ligand; nature of metal salts, concentration of the combination of metal/ligand; nature of solvent and nature of the substrate. The highest rate activity is given by the in-situ complex formed by ligand L1 and metal salt Cu(CH3CO2)2 which is equal to 19.04 μmol.L-1min-1.