Synthesis of Borocations and their Catalytic Application in Cyanosilylation

Abstract

Boron chemistry has gained enormous traction in the last 50 years on account of the versatility of boron. Cationic boron species known as borocations have been recent favourites in organometallic chemistry due to their high electrophilic character and, thus, greater reactivity. Borocations have, therefore, been explored in organic transformations, including hydrosilylation and hydroboration. In addition, many of these species have been known to show thermochromism and luminescent properties, allowing for their use in photo-physical studies. Among the borocations, the reactivity of boronium ions has been explored to a relatively lesser extent in contrast to boreniums. Herein, we have synthesized two boronium-like cations with varying counter-ions using N,N’-dimesitylethanediamine as the ligand. The influence of the ligand on the steric and electronic properties of the system and, hence, the boron centre has been well studied. Using literature precedence, we have justified the classification of our borocations as boronium-like cations. Furthermore, the molecular structure of the borocation C2 has been successfully established using single crystal X-ray diffraction, and both the cations C2 and C3 have been characterized thoroughly using analytical tools, including NMR, IR, and HRMS. The Lewis acidic nature of both the cations has been tested via the Gutmann-Beckett method, and they have been used as efficient catalysts for the cyanosilylation of various aldehydic substrates.