Tetra(o-tolyl)diborane(4), 1, was synthesized and characterized experimentally as well as theoretically by density functional theory (DFT) calculations. Exposure of 1 to H-2 (1 bar) at room temperature afforded the corresponding di(o-tolyl)hydroborane through cleavage of the H-H and B-B bonds. DFT calculations suggested a diarylboryl anion character for the transition state.