High-valent mononuclear metal-hydroxide species have been widely implicated as intermediates in several enzymatic catalytic cycles, e.g. the Fe(IV)-hydroxo species known as compound II for cytochrome P450.Several biomimetic models of high-valent metal-hydroxide complexes have been synthesized and characterized by employing first-row transition metals such as Mn, Fe, Co and Cu, behaving in most cases as powerful electrophilic oxidants capable of performing hydrogen atom abstraction with O-H or C-H bonds.<br/>Despite the existence of analogous compounds based on third-row transition metal such as Au, their capability to perform O-H and C-H bond activation has not been investigated. Au(III) complexes have been proved to be effective catalysts for many classes of reactions, often postulating the involvement of Au(III)-oxo species as the active oxidants, but never of the corresponding hydroxo-species.<br/>A stable Au(III)-OH complex shown to react readily with either phenolic O-H and weak hydrocarbon C-H bonds at 25°C. The hydrogen atom abstraction step was identified by observing the formation of stable phenoxyl radicals by electronic absorption and electron paramagnetic resonance. The corresponding oxidized products and their kinetics of formation have been investigated by electronic absorption spectroscopy, gas chromatography and <sup>1</sup>H-NMR. These results give insights on the possible role of Au(III)-OH species as key active intermediates in oxidative catalysis.

High-valent gold-hydroxo complex capable of O-H and C-H bond oxidation

2019 Fall National Meeting

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