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

Dehydropolymerisation of methylamine borane (H(3) B⋠NMeH(2) ) using the well-known iron amido complex [(PNP)Fe(H)(CO)] (PNP=N(CH(2) CH(2) PiPr(2) )(2) ) (1) gives poly(aminoborane)s by a chain-growth mechanism. In toluene, rapid dehydrogenation of H(3) B⋠NMeH(2) following first-order behaviour as a limiting case of a more general underlying Michaelis-Menten kinetics is observed, forming aminoborane H(2) B=NMeH, which selectively couples to give high-molecular-weight poly(aminoborane)s (H(2) BNMeH)(n) and only traces of borazine (HBNMe)(3) by depolymerisation after full conversion. Based on a series of comparative experiments using structurally related Fe catalysts and dimethylamine borane (H(3) B⋠NMe(2) H) polymer formation is proposed to occur by nucleophilic chain growth as reported earlier computationally and experimentally. A silyl functionalised primary borane H(3) B⋠N(CH(2) SiMe(3) )H(2) was studied in homo- and co-dehydropolymerisation reactions to give the first examples for Si containing poly(aminoborane)s.