Sulfur oxygenation in biomimetic non-heme iron-thiolate complexes

• Published in: Dalton transactions : an international journal of inorganic chemistry 2012-08, Vol.41 (36), p.1883-1899
• Main Authors: McQuilken, Alison C, Goldberg, David P
• Format: Article
• Language: English
• Subjects: Biomimetic Materials - chemistry; Biomimetic Materials - metabolism; Catalytic Domain; Coordination Complexes - chemistry; Crystallography, X-Ray; Cysteine; Enzymes; Ferric Compounds - chemistry; Ferrous Compounds - chemistry; Focusing; Heme - chemistry; Hydro-Lyases - metabolism; Iron; Ligands; Molecular Conformation; Oxidoreductases - metabolism; Oxygen - chemistry; Oxygenation; Sulfhydryl Compounds - chemistry; Sulfur; Sulfur - chemistry; Transformations
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c2dt30806a

The S-oxygenation of cysteine with dioxygen to give cysteine sulfinic acid occurs at the non-heme iron active site of cysteine dioxygenase. Similar S-oxygenation events occur in other non-heme iron enzymes, including nitrile hydratase and isopenicillin N synthase, and these enzymes have inspired the development of a class of [N x S y ]-Fe model complexes. Certain members of this class have provided some intriguing examples of S-oxygenation, and this article summarizes these results, focusing on the non-heme iron( ii / iii )-thiolate model complexes that are known to react with O 2 or other O-atom transfer oxidants to yield sulfur oxygenates. Key aspects of the synthesis, structure, and reactivity of these systems are presented, along with any mechanistic information available on the oxygenation reactions. A number of iron( iii )-thiolate complexes react with O 2 to give S-oxygenates, and the degree to which the thiolate sulfur donors are oxidized varies among the different complexes, depending upon the nature of the ligand, metal geometry, and spin state. The first examples of iron( ii )-thiolate complexes that react with O 2 to give selective S-oxygenation are just emerging. Mechanistic information on these transformations is limited, with isotope labeling studies providing much of the current mechanistic data. The many questions that remain unanswered for both models and enzymes provide strong motivation for future work in this area. This Perspective gives an overview of non-heme iron-thiolate model complexes and relevant enzyme active sites that undergo sulfur oxygenation.