An Organoborate Monoxide Radical

The boron monoxide radical has emerged as a fascinating molecule and a short-lived intermediate, previously observed only under matrix isolation conditions. In this study, we report the successful synthesis and characterization of a stable organic boron monoxide radical, achieved through the reaction of a diboron (6) dianion with nitric oxide (NO). This oxygen-centered radical is uniquely functionalized and stabilized by a triaryl-substituted boryl group. Comprehensive characterization was performed using various spectroscopic and structural techniques, including electron paramagnetic resonance (EPR) spectroscopy and single-crystal X-ray diffraction analysis. Remarkably, this oxygen-centered radical is stabilized by the K cation and exhibits significant stability under argon at room temperature, showing no self-dimerization even when heated or exposed to UV light. However, it can dimerize to form peroxide species when the K cation is fully encapsulated. Furthermore, it can mimic transition-metal complexes by mediating NO coupling to form a boryl hyponitrite (N₂O₂^2-) derivative. Finally, this boron monoxide radical also shows promising catalytic potential in Sn-Sn coupling reactions.