The Metal or the Ligand? The Preferred Locus for Redox Changes in Oxygen Atom Transfer Reactions of Rhenium Amidodiphenoxides.

Author(s) Hoffman, J.M.; Oliver, A.G.; Brown, S.N.
Journal J Am Chem Soc
Date Published 2017 Mar 16
Abstract

The rhenium(V) oxo complex oxo(triphenylphosphine) (bis(3,5-di-tert-butyl-2-phenoxo)amido)rhenium(V), (ONO(Cat))ReO(PPh3), reacts with molecular oxygen to give triphenylphosphine oxide and the dimeric rhenium(VII) complex fac,anti-(ONO(Cat))Re(O)(μ-O)2Re(O)(ONO(Cat)). The ONO ligand adopts an unusual fac geometry, presumably to maximize π donation to rhenium; strong π donation is substantiated by the intraligand bond distances (metrical oxidation state = -2.24(9)). Addition of the N-heterocyclic carbene ligand IMes to fac,anti-(ONO(Cat))Re(O)(μ-O)2Re(O)(ONO(Cat)) cleaves the dimer into monomeric C1-symmetric fac-(ONO(Cat))ReO2(IMes). The monorhenium(VII) complex is deoxygenated by PMe2Ph to give the rhenium(V) compound (ONO(Cat))ReO(IMes), which can be independently prepared by ligand substitution of (ONO(Cat))ReO(PPh3). The degree of stereochemical rigidity exhibited by the dioxo compound, as established by dynamic NMR spectroscopy, excludes the intermediacy of mer-(ONO(Q))Re(V)O2(IMes) in this oxygen atom transfer reaction. Thus, oxygen atom transfer takes place preferentially by direct reduction of the oxorhenium(VII) moiety (classical oxygen atom transfer) rather than through initial internal electron transfer and ligand-centered reduction of an oxorhenium(V)-iminoquinone.

DOI 10.1021/jacs.7b00985
ISSN 1520-5126
Citation Hoffman JM, Oliver AG, Brown SN. The Metal or the Ligand? The Preferred Locus for Redox Changes in Oxygen Atom Transfer Reactions of Rhenium Amidodiphenoxides. J Am Chem Soc. 2017.

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