A chromium(III)-superoxo complex in oxygen atom transfer reactions as a chemical model of cysteine dioxygenase.
Metal-superoxo species are believed to play key roles in oxygenation reactions by metalloenzymes. One example is cysteine dioxygenase (CDO) that catalyzes the oxidation of cysteine with O(2), and an iron(III)-superoxo species is proposed as an intermediate that effects the sulfoxidation reaction. We now report the first biomimetic example showing that a chromium(III)-superoxo complex bearing a macrocyclic TMC ligand, [Cr(III)(O(2))(TMC)(Cl)](+), is an active oxidant in oxygen atom transfer (OAT) reactions, such as the oxidation of phosphine and sulfides. The electrophilic character of the Cr(III)-superoxo complex is demonstrated unambiguously in the sulfoxidation of para-substituted thioanisoles. A Cr(IV)-oxo complex, [Cr(IV)(O)(TMC)(Cl)](+), formed in the OAT reactions by the chromium(III)-superoxo complex, is characterized by X-ray crystallography and various spectroscopic methods. The present results support the proposed oxidant and mechanism in CDO, such as an iron(III)-superoxo species is an active oxidant that attacks the sulfur atom of the cysteine ligand by the terminal oxygen atom of the superoxo group, followed by the formation of a sulfoxide and an iron(IV)-oxo species via an O-O bond cleavage.
Department of Bioinspired Science, Ewha Womans University, Seoul 120-750, Korea.
Jaeheung
J
Cho
Jaeyoung
J
Woo
Wonwoo
W
Nam
D040761:Biomimetic Materials / Q000737:chemistry*; D002857:Chromium / Q000737:chemistry*; D018360:Crystallography, X-Ray; D050558:Cysteine Dioxygenase / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry*; D047028:Macrocyclic Compounds / Q000737:chemistry*; D008958:Models, Molecular; D010100:Oxygen / Q000737:chemistry*
D005290:Ferric Compounds; D047028:Macrocyclic Compounds; D002857:Chromium; D050558:Cysteine Dioxygenase; D010100:Oxygen