Evidence for a terminal Pt(iv)-oxo complex exhibiting diverse reactivity

Abstract

Many important biological and chemical processes, including photocatalytic water oxidation to molecular oxygen (of interest as a route to artificial photosynthesis) and the activation of dioxygen on metal surfaces, are thought to involve transition metal terminal oxo complexes. Poverenov et al. now report the synthesis of a platinum based oxidizing reagent with potentially useful characteristics. It's a d6 Pt(IV) terminal oxo complex that is not stabilized by an electron accepting ligand framework, and so exhibits reactivity as both an inter- and intra-molecular oxygen donor and as an electrophile. It also undergoes water activation to produce a terminal dihydroxo complex, which may be of relevance to the mechanism of water oxidation and other catalytic reactions. Terminal oxo complexes of transition metals are important in biological and chemical processes, for example, the catalytic oxidation of organic molecules and the activation of dioxygen on metal surfaces are thought to involve oxo complexes. This paper explored the reactivity of a d6 Pt(IV) complex, a dn (n > 5) terminal oxo complex that is not stabilized by an electron withdrawing ligand framework. The complex exhibits reactivity as an inter- and intra-molecular oxygen donor and as an electrophile. Terminal oxo complexes of transition metals have critical roles in various biological and chemical processes1,2. For example, the catalytic oxidation of organic molecules3,4, some oxidative enzymatic transformations5,6,7, and the activation of dioxygen on metal surfaces8 are all thought to involve oxo complexes. Moreover, they are believed to be key intermediates in the photocatalytic oxidation of water to give molecular oxygen, a topic of intensive global research aimed at artificial photosynthesis and water splitting9,10,11,12,13. The terminal oxo ligand is a strong π-electron donor, so it readily forms stable complexes with high-valent early transition metals. As the d orbitals are filled up with valence electrons, the terminal oxo ligand becomes destabilized2. Here we present evidence for a dn (n > 5) terminal oxo complex that is not stabilized by an electron withdrawing ligand framework. This d6 Pt(iv) complex exhibits reactivity as an inter- and intramolecular oxygen donor and as an electrophile. In addition, it undergoes a water activation process leading to a terminal dihydroxo complex, which may be relevant to the mechanism of catalytic reactions such as water oxidation.