Transition-Metal-Free Dehydropolymerization of Phosphine-Boranes at Ambient Temperature

Stoichiometric reaction of phosphine-borane adducts RR'PH center dot BH3 (R=Ph, R'=H, Ph, Et, and R=R'=Bu-t) with the strong acid HNTf2 (Tf=SO2CF3) leads to H-2 elimination and the formation of the triflimido derivatives, RR'PH center dot BH2(NTf2). Subsequent deprotonation by using bases, such as diisopropylethylamine or the carbene IPr (IPr=N,N'-bis(2,6-diisopropylphenyl)imidazol-2-ylidene), led to the formation of P-mono- or -disubstituted polyphosphinoboranes [RR'P-BH2](n). Evidence for the intermediacy of transient phosphinoborane monomers, RR'PBH2, was provided by trapping reactions.

Automated summary

Reaction of phosphine-borane adducts with strong acid leads to triflimido derivatives, followed by subsequent reaction with bases forming polyphosphinoboranes. Evidence of transient phosphinoborane monomers as intermediates.