Comparative reactivity of diaqua(tetraamine)cobalt(II) complexes promoted hydrolysis of phosphate diester

Three diaqua(tetraamine)Co(III) complexes, [(N-4)Co(OH2)(2)]-(ClO4)(3).xH(2)O, N-4=(en)(2), (tn)(2), (tme)(2), were synthesized and characterized, and investigated with respect to their effects on the hydrolysis of bis(4-nitrophenyl) phosphate (BNPP) at different pH and at 30 degreesC. The results indicated that the three complexes accelerated the hydrolysis of BNPP, their active species are all aquo-hydroxo forms and the activities of the complexes differ greatly as promoters for the hydrolysis of BNPP; the order follows: [(en)(2)Co(OH2)(2)](3+) < [(tn)(2)CO(OH2)(2)](3+) < [(tme)(2)Co(OH2)(2)](3+). These observations may be due to the differences in the isomeric configurations and the structures of the complexes.