Synthesis and Characterization of Carboxylate-Rich Complexes Having the {Fe₂(μ-OH)₂(μ-O₂CR)}³⁺ and {Fe₂(μ-O)(μ-O₂CR)}³⁺ Cores of O₂-Dependent Diiron Enzymes

The {Fe2(μ-OH)2(μ-O2CR)}3+ and {Fe2(μ-O)(μ-O2CR)}3+ cores of the carboxylate-bridged diiron(III) centers in the enzyme active sites were reproduced by small molecule model complexes that were prepared through direct oxygenation of the mononuclear iron(II) complexes. Upon oxygenation of [Fe(O2CArTol)2(Hdmpz)2], where -O2CArTol is 2,6-di(p-tolyl)benzoate and Hdmpz is 3,5-dimethylpyrazole, [Fe2(μ-OH)2(μ-O2CArTol)(O2CArTol)3(OH2)(Hdmpz)2] was generated and characterized to share close physical properties with sMMOHox, including δ = 0.45 (2) mm/s, ΔEQ = 1.21 (2) mm/s, and J = −7.2 (2) cm-1. The compound [Fe2(μ-O)(μ-O2CAr4-FPh)(O2CAr4-FPh)3(Hdmpz)3], where -O2CAr4-FPh is 2,6-di(4-fluorophenyl)benzoate, with δ = 0.51 (2) mm/s, ΔEQ = 1.26 (2) mm/s, and J = −117.4 (1) cm-1, was isolated as the oxygenation product of [Fe(O2CAr4-FPh)2(Hdmpz)2].