Unveiling the urease like intrinsic catalytic activities of two dinuclear nickel complexes towards the in situ syntheses of aminocyanopyridines

Abstract

Designing metal complexes as functional models for metalloenzymes remains one of the main targets in synthetic bioinorganic chemistry. Furthermore, the utilization of the product(s) derived from the catalytic reaction for subsequent organic transformation that occurs in biological systems is an even more difficult challenge for biochemists. Urease, the most efficient enzyme known, catalyzes the hydrolysis of urea and it contains an essential dinuclear Ni^II cluster in the active site. Inspired by the catalytic properties of urease, two dinickel(II) complexes viz. Ni₂L¹₂(OAc)₂(H₂O) (1) and Ni₂L²₂(OAc)₂(H₂O) (2) [HL1 = 2,4-dimethyl-6-{[(2′-dimethyl aminoethyl)methylamino]methyl}-phenol and HL2 = 2,4-dichloro-6-{[(2′-dimethyl aminoethyl)methylamino]methyl}-phenol] have been synthesized and characterized in this report. Both the complexes have shown the urease kind of activity with the liberation of ammonia from urea in aqueous solution. The plausible mechanistic pathway and kinetics of the reactions have been studied. Besides, the liberated ammonia has been utilized in the one-pot synthesis of biologically active products like 2-amino-3-cyanopyridines and their derivatives in aqueous medium with excellent yields.