Direct access to a cAAC-supported dihydrodiborene and its dianion

Abstract

The two-fold reduction of (cAAC)BHX₂ (cAAC = 1-(2,6-diisopropylphenyl)-3,3,5,5-tetramethylpyrrolidin-2-ylidene; X = Cl, Br) provides a facile, high-yielding route to the dihydrodiborene (cAAC)₂B₂H₂. The (chloro)hydroboryl anion reduction intermediate was successfully isolated using a crown ether. Overreduction of the diborene to its dianion [(cAAC)₂B₂H₂]²⁻ causes a decrease in the B–B bond order whereas the B–C bond orders increase.