Modeling TauD- J: A high-spin nonheme oxoiron(IV) complex with high reactivity toward C-H bonds

High-spin oxoiron(IV) species are often implicated in the mechanisms of nonheme iron oxygenases, their C-H bond cleaving properties being attributed to the quintet spin state. However, the few available synthetic S = 2 Fe^IV=O complexes supported by polydentate ligands do not cleave strong C-H bonds. Herein we report the characterization of a highly reactive S = 2 complex, [Fe^IV(O)(TQA)(NCMe)]²⁺ (2) (TQA = tris(2-quinolylmethyl)amine), which oxidizes both C-H and C=C bonds at -40 °C. The oxidation of cyclohexane by 2 occurs at a rate comparable to that of the oxidation of taurine by the TauD-J enzyme intermediate after adjustment for the different temperatures of measurement. Moreover, compared with other S = 2 complexes characterized to date, the spectroscopic properties of 2 most closely resemble those of TauD-J. Together these features make 2 the best electronic and functional model for TauD-J to date.