Mono iodosobenzene

A recent summary25 of the activation of O2 by cytochrome P-450 (an iron(III)-heme protein with a axial cysteine thiolate ligand) concludes that the reactive form of this mono-oxygenase also contains an oxene-ferryl group (RS)(por)FeV=O. The mono-oxygenase chemistry of cytochrome P-450 has been modeled via the use of (TPP)Fei lCl(TPP=tetraphenylporphyrin) and (OEP)Fe JCl (OEP=octaethylporphyrin) with peracids,26,27 iodosobenzene,26,27... 

V04] (-537 ppm) was left in the NMR spectrum of a solution of V0(MA)2. As the pH was lowered, both bis- and mono-maltolato complexes (-496 and -510 ppm, respectively) appeared and the [V04] (at -538 -560 ppm in various pH) decreased. Similar results were also obtained from the chemical analogue of VO(ma)2, bis(kojato)oxovanadium(IV) (VO(ka)2) [170]. The oxidation of VO(ma)2 can be slowed down dramatically in the presence of good donor ligands such as pyridine (py) via the formation of six coordinate adducts (e.g., VO(ma)2 py), and it could be indefinitely suppressed with 5-10 equiv of ascorbic acid. The oxidation could be speeded up significantly by either iodosobenzene or hydrogen peroxide [169]. 

Summarizing the information disclosed in the section above, one notes that polyoxometalates appear to be versatile oxidation catalysts capable of activating various mono-oxygen donors such as iodosobenzene, periodate, ozone, nitrous oxide, and sulfoxides. Some of these reactions are completely new from both a synthetic and mechanistic point of view. The various reaction pathways expressed are also rather unusual and point to the many options and reaction pathways available for oxidation catalyzed by polyoxometalates. 

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