Kinetic study of the displacement of water in diaquo[N,N′-ethylene-bis(salicylideneiminate)]cobalt(III) monocation by various nucleophiles

The water substitution reactions of the monocation Co(III)(H 2 O) 2 (salen) + [salen = N,N′-ethylene-bis(salicylideneiminate)] were studied in aqueous solution. The nucleophiles used were pyridine, thiourea, morpholine, aniline, imidazole, NCO − , HSO 3 − , S 2 O 3 2− . The kinetics of mono-substitution reactions were found to be very rapid, with second order rate constants nearly independent of the nature of the incoming ligand. A comparison is made with the corresponding reactions of Co(III)hematoporphyrin and some other macrocyclic complexes.