Urea decomposition facilitated by a urease model complex: a theoretical investigation

Abstract

Density functional theory calculations were used to examine the role of the urease model complex [Ni₂(bdptz)(µ-OH)(µ-H₂O)(H₂O)₂](OTs)₃ (A) (bdptz = 1,4-bis(2,2′-dipyridylmethyl)-phthalazine; OTs = tosylate) in the degradation of urea. An elimination mechanism that converts urea to ammonium cyanate was investigated in detail. The lowest energy pathway involves urea coordination through the oxygen atom to a Ni center followed by protonation of a urea NH₂ group by the bridging water ligand. Subsequent rotation of the protonated urea, followed by deprotonation of the NH₂ by a bridging OH ligand generates the bound, disproportionated urea substrate, HNCONH₃, from which ammonium cyanate was produced.