Reactions of a stable dialkylphosphinyl radical, 2,2,5,5-tetrakis(trimethylsilyl)-1-phosphacyclopentane-1-yl (1) with BH3-Lewis base (LB) adducts [BH3(LB)] provided hydrophosphine 3, hydrophosphine-borane complex 4, and mu-phosphinodiborane(6) 5 as detectable products via hydrogen abstraction. Theoretical studies revealed that B-H bonds in BH3 become considerably weaker upon coordination of 1, which reflected in facile hydrogen abstraction from phosphinyl radical-BH3 complex.