A Biomimetic System for Studying Salicylate Dioxygenase

We report the characterization of [Fe(T1Et4iPrIP)(sal)] (2) (T1Et4iPrIP = tris(1-ethyl-4-isopropyl-imidazolyl)phosphine; sal^2- = salicylate dianion), which serves as a model for substrate-bound salicylate dioxygenase (SDO). Complex 2 crystallizes in the monoclinic space group P2₁/n with a = 10.7853(12) Å, b = 16.5060(19) Å, c = 21.217(2) Å, β = 94.489(2)°, and V = 3765.5(7) ų. The structure consists of Fe^II bonded in distorted square pyramidal geometry (τ = 0.32) with two salicylate oxygens and two T1Et4iPrIP nitrogens serving as the base and the apical position occupied by the other ligand nitrogen. [Fe(T1Et4iPrIP)(OTf)₂] (1), the precursor for 2, catalyzes the cleavage of 1,4-dihydroxy-2-naphthoate in the presence of O₂. Complex 1 is also capable of cleaving the salicylate aromatic ring in the presence of H₂O₂. The progression of this reaction toward product formation involves an Fe^III-phenoxide species.