Amplifying Lewis acidity by oxidation: leveraging the redox-activity of bis(3,6-di-tert-butyl-catecholato)silane

Abstract

Bis(catecholato)silanes were showcased as strong Lewis acids, while their inherent redox activity remained unexplored in this context. In the present work, we study the oxidation of monomeric bis(3,6-di-tert-butyl-catecholato)silane (1), leading to the Lewis superacidic radicalic silylium ionradical 1˙⁺ (FIA 784 kJ mol⁻¹). Oxidation of 1 with [N(p-C₆H₄Br)₃][B(C₆F₅)₄] yielded [1][B(C₆F₅)₄], displaying strong catalytic activity in the Friedel–Crafts-dimerization, hydrodeoxygenation and carbonyl-olefin-metathesis. It demonstrates how Lewis acidity can be amplified through oxidation without needing an add-on redox-active substituent. Instead, it synergizes the constraining effect of catecholates with their inherent redox non-innocence to unlock enhanced catalytic performance.