A synthetic model of the putative Fe(II)-iminobenzosemiquinonate intermediate in the catalytic cycle of o-aminophenol dioxygenases.

Michael M Bittner, Sergey V Lindeman, Adam T Fiedler

Index: J. Am. Chem. Soc. 134(12) , 5460-3, (2012)

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Abstract

The oxidative ring cleavage of aromatic substrates by nonheme Fe dioxygenases is thought to involve formation of a ferrous-(substrate radical) intermediate. Here we describe the synthesis of the trigonal-bipyramdial complex Fe((Ph2)Tp)(ISQ(tBu)) (2), the first synthetic example of an iron(II) center bound to an iminobenzosemiquinonate (ISQ) radical. The unique electronic structure of this S = 3/2 complex and its one-electron oxidized derivative ([3](+)) have been established on the basis of crystallographic, spectroscopic, and computational analyses. These findings further demonstrate the viability of Fe(2+)-ISQ intermediates in the catalytic cycles of o-aminophenol dioxygenases.