Homolytic Cleavage of a B−B Bond by the Cooperative Catalysis of Two Lewis Bases: Computational Design and Experimental Verification

Density functional theory (DFT) investigations revealed that 4‐cyanopyridine was capable of homolytically cleaving the B−B σ bond of diborane via the cooperative coordination to the two boron atoms of the diborane to generate pyridine boryl radicals. Our experimental verification provides supportive evidence for this new B−B activation mode. With this novel activation strategy, we have experimentally realized the catalytic reduction of azo‐compounds to hydrazine derivatives, deoxygenation of sulfoxides to sulfides, and reduction of quinones with B2(pin)2 at mild conditions. Breaking good: The diborane B−B bond can be homolytically cleaved via the cooperative catalysis of two 4‐cyanopyridine molecules. Using this combination of a diborane (B2(pin)2) and 4‐cyanopyridine also allows the catalytic reduction of the N=N double bond of azo‐compounds to hydrazine derivatives, deoxygenation of sulfoxides to sulfides, and reduction of quinones under mild conditions.