Mononuclear, dinuclear nickel(II) and heterodinuclear Zn(II)Ni(II) complexes as models for the active site of phosphatase

Mononuclear and dinuclear nickel(II) complexes and heterodinuclear Zn(II)Ni(II) complexes of the ligand 3,4:9, 10-dibenzo-1,12[N,N'bis{4-methyl-1-oxa)-6, 6'-formyl}-2-benzyldiaza]-5,8-dioxacyclotetradecane were prepared. The structure of the complex [NiL1a] was solved by X-ray crystallography. The electrochemical reduction processes of the mononuclear nickel(II) and the heterobinuclear zinc(II)nickel(II) complexes were irreversible and that the binuclear nickel(11) complexes showed quasireversible reduction processes and irreversible oxidation processes. Kinetics of hydrolysis of 4-nitrophenyl phosphate catalyzed by the complexes showed pseudo first order processes with rate constants in the range 2 x 10(-5) s(-1) for the mononuclear nickel(II) complexes and in the range 8 x 10(-4) s(-1) for the homo binuclear nickel(II) and heterobinuclear zinc(II)nickel(II) complexes. (C) 2003 Elsevier B.V. All rights reserved.