A Nonheme Iron(III) Superoxide Complex Leads to Sulfur Oxygenation.

A new alkylthiolate-ligated nonheme iron complex, Fe II (BNPA Me2 S)Br ( 1 ), is reported. Reaction of 1 with O 2 at -40 °C, or reaction of the ferric form with O 2 •- at -80 °C, gives a rare iron(III)-superoxide intermediate, [Fe III (O 2 )(BNPA Me2 S)] + ( 2 ), characterized by UV-vis, 57 Fe Mössbauer, ATR-FTIR, EPR, and CSIMS. Metastable 2 then converts to an S-oxygenated Fe II (sulfinate) product via a sequential O atom transfer mechanism involving an iron-sulfenate intermediate. These results provide evidence for the feasibility of proposed intermediates in thiol dioxygenases.