Addition of Dioxygen to an N₄S(thiolate) Iron(II) Cysteine Dioxygenase Model Gives a Structurally Characterized Sulfinato–Iron(II) Complex

The non-heme iron enzyme cysteine dioxygenase (CDO) catalyzes the S-oxygenation of cysteine by O2 to give cysteine sulfinic acid. The synthesis of a new structural and functional model of the cysteine-bound CDO active site, [FeII(N3PyS)­(CH3CN)]­BF4 (1) is reported. This complex was prepared with a new facially chelating 4N/1S­(thiolate) pentadentate ligand. The reaction of 1 with O2 resulted in oxygenation of the thiolate donor to afford the doubly oxygenated sulfinate product [FeII(N3PySO2)­(NCS)] (2), which was crystallographically characterized. The thiolate donor provided by the new N3PyS ligand has a dramatic influence on the redox potential and O2 reactivity of this FeII model complex.