Activation of H2 and Et3SiH by the Borinium Cation [Mes2B]+: Avenues to Cations [MesB(μ-H)2(μ-Mes)BMes]+ and [H2B(μ-H)(μ-Mes)B(μ-Mes)(μ-H)BH2]+

Reaction of dihydrogen and the borinium cation salt [Mes2B]­[B­(C6F5)4] gave an arene-stabilized mesityl-borenium cation, which isotopically scrambles HD. Similarly, reaction with triethylsilane gave the diboranium cation [MesB­(μ-H)2(μ-Mes)­BMes]+ featuring three bridge-bonds between two boron centers. Reaction of same (Mes2BH)2 with Brønsted acid also afforded the same diboranium whereas the corresponding reaction with (MesBH2)2 yielded the triboron cation [H2B­(μ-H)­(μ-Mes)­B­(μ-Mes)­(μ-H)­BH2]+.