Dioxygen Binding and Activation Reactive Intermediates

Andrew S. Borovik, PaulJ. Zinn, and Matthew K. Zart 

Oxidation chemistry has attracted the attention, and in many cases the passion, of chemists for well over a century. This interest has been fueled by several competing areas of science, with organic and biochemistry being the most prominent today. A link into these research areas is transition metal ions, which are intimately involved in several oxidative transformations. Understanding the relationships between metal ions and oxidants is necessary in the development of more efficient and clean oxidative processes. 

Activation of Small Molecules. Edited by William B. Tolman Copyright C) 2006 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim ISBN 3-527-31312-5 

In the resting state, the iron center is six-coordinate with an axially bonded water occupying the final coordination site (A). The catalytic cycle starts with binding of the camphor substrate within the active site, which causes dissociation of the water from the Fe(III) complex. Camphor is not directly bonded to the iron, but docks proximal to the metal center through hydrogen bonds. 

The dissociation of water produces a five-coordinate Fe(III) complex (B) that can be reduced to an Fe(II) analog. Ferrous P450cam (C) readily binds dioxygen to form the oxy form of the enzyme. Dioxygen binds in a bent end-on mode (t/ -Oz) with the iron center formally oxidized to Fe(III) and the O2 reduced by one electron to superoxide (D). Addition of a second electron from putidaredox-in follows to further reduce the complex to an Fe(III)-peroxo species (E). Proton transfer is required before the cleavage of the 0-0 bond an Fe(III)-hydroperoxo 

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Borovik, A. S. Zinn, P. J. Zart, M. K. Dioxygen binding and activation reactive intermediates. In Activation of Small Molecules, Tolman, W. B. Wiley-VCH Weinheim, 2006 pp 187-234. 

I 6 Dioxygen Binding and Activation Reactive Intermediates 6.1.2.3 Flow of Electrons and Protons... 

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