Taming the Piers–Rubinsztajn Reaction: Beyond B(C6F5)3

The strong fluoroaryl borane Lewis acid B(C6F5)3 (FAB) is known to catalyze the Piers–Rubinsztajn (PR) reaction (coupling of silyl hydrides with alkoxysilanes), among other related reactions relevant to the formation of commercially useful siloxane intermediates or cured siloxane networks. However, the catalyst induces undesired self-cure of Si–H-containing siloxanes, limiting its industrial applicability in polymer systems. Despite the versatility of this catalyst, there has been relatively little focus on optimizing the performance of the catalyst through structural modifications. In this work, we show that simple changes, either steric or electronic, to the structure of the Lewis acid help modulate the catalytic activity of such Lewis acids, eliminating the undesirable self-cure and improving their usefulness in reactions of industrial interest.