From an Electron-Rich Bis(boraketenimine) to an Electron-Poor Diborene

The reaction of the bisboracumulene (CAAC)(2)B-2 (CAAC=1-(2,6-diisopropylphenyl)-3,3,5,5-tetramethylpyrrolidin-2-ylidene) with excess tert-butylisocyanide resulted in complexation of the isocyanide at boron. Though this compound might be formally drawn with a lone pair on boron, these electrons are highly delocalized throughout a conjugated -network consisting of the -acidic CAAC and isocyanide ligands. Heating this compound to 110 degrees C liberated the organic periphery of both isocyanide ligands, yielding the first example of a dicyanodiborene. Cyclic voltammetry conducted on this diborene indicated the presence of reduction waves, making this compound unique among diborenes, which are otherwise highly reducing.