Widening the Landscape of Small Molecule Activation with Gold-Aluminyl Complexes: A Systematic Study of E−H (E=O, N) Bonds, SO2 and N2O Activation

Abstract

The electronic features of gold-aluminyl complexes have been thoroughly explored. Their similarity with Group 14 dimetallenes and other metal-aluminyl complexes suggests that their reactivity with small molecules beyond carbon dioxide could be accessed. In this work, the reactivity of the [tBu3PAuAl(NON)] (NON=4,5-bis(2,6 diisopropylanilido)-2,7-ditert-butyl-9,9-dimethylxanthene) complex towards water, ammonia, sulfur dioxide and nitrous oxide is computationally explored. The reaction mechanisms computed for each substrate strongly suggest that all activation processes are in principle experimentally feasible. Electronic structure analysis highlights that, in all cases, the reactivity is driven by the presence of the poorly polarized electron-sharing gold-aluminyl bond, which induces a radical-like reactivity of the complex towards all the substrates. A flat topology of the potential energy surface (PES) has been found for the reaction with N2O, where two almost isoenergetic transition states can be located along the same reaction coordinate with different geometries, suggesting that the N2O binding mode may not be a good indicator of the nature of N2O activation in a cooperative bimetallic reactivity. In addition, the catalytic potentialities of these complexes have been explored in the framework of nitrous oxide reduction. The study reveals that the [tBu3PAuAl(NON)] complex might be an efficient catalyst towards oxidation of phosphines (and boranes) via N2O reduction. These findings underline recurring trends in the novel chemistry of gold-aluminyl complexes and call for experimental feedbacks.