An Isolable Potassium Salt of a Borasilene-Chloride Adduct

Among the variety of isolable compounds with multiple bonds involving silicon, examples of compounds that contain silicon-boron double bonds (borasilenes) still remain relatively rare. Herein, we report the synthesis of the potassium salt of a chloride adduct of borasilene 1 ([2]^- ), which was obtained as an orange crystalline solid. Single-crystal X-ray diffraction analysis and reactivity studies on [2]^- confirmed the double-bond character of the Si=B bond as well as the reduced Lewis acidity, which is due to the coordination of Cl^- to the boron center. A thermal reaction of [2]^- afforded a bicyclic product by formal intramolecular C-H insertion across the Si=B bond of 1, which was corroborated by a theoretical study.