Dehydropolymerisation of Methylamine Borane and an N-Substituted Primary Amine Borane Using a PNP Fe Catalyst.

Dehydropolymerisation of methylamine borane (H B⋅NMeH ) using the well-known iron amido complex [(PNP)Fe(H)(CO)] (PNP=N(CH CH PiPr ) ) (1) gives poly(aminoborane)s by a chain-growth mechanism. In toluene, rapid dehydrogenation of H B⋅NMeH following first-order behaviour as a limiting case of a more general underlying Michaelis-Menten kinetics is observed, forming aminoborane H B=NMeH, which selectively couples to give high-molecular-weight poly(aminoborane)s (H BNMeH) and only traces of borazine (HBNMe) by depolymerisation after full conversion. Based on a series of comparative experiments using structurally related Fe catalysts and dimethylamine borane (H B⋅NMe H) polymer formation is proposed to occur by nucleophilic chain growth as reported earlier computationally and experimentally.