Catalytic Dehydrogenation of Amine-Boranes using Geminal Phosphino-Boranes

The reaction of the intramolecular frustrated Lewis pair (FLP) tBu₂PCH₂BPh₂ with the amine-boranes NH3 center dot BH3 and Me2NH center dot BH3 leads to the formation of the corresponding FLP-H₂ adducts as well as novel five-membered heterocycles that result from capturing the in situ formed amino-borane by a second equivalent of FLP. The sterically more demanding tBu₂PCH₂BMes₂ does not form such a five-membered heterocycle when reacted with Me₂NH•BH₃ and its H₂ adduct liberates dihydrogen at elevated temperatures, promoting the metal-free catalytic dehydrogenation of amine-boranes.