Abstract
The sigma amine-borane complexes [Rh(L1)(η(2) :η(2) -H(3) B⋅NRH(2) )][OTf] (L1=2,6-bis-[1-(2,6-diisopropylphenylimino)ethyl]pyridine, R=Me, Et, (n) Pr) are described, alongside [Rh(L1)(NMeH(2) )][OTf]. Using R=Me as a pre-catalyst (1 mol %) the dehydropolymerization of H(3) B ⋅ NMeH(2) gives [H(2) BNMeH](n) selectively. Added NMeH(2) , or the direct use of [Rh(L1)(NMeH(2) )][OTf], is required for initiation of catalysis, which is suggested to operate through the formation of a neutral hydride complex, Rh(L1)H. The formation of small (1-5 nm) nanoparticles is observed at the end of catalysis, but studies are ambiguous as to whether the catalysis is solely nanoparticle promoted or if there is a molecular homogeneous component. [Rh(L1)(NMeH(2) )][OTf] is shown to operate at 0.025 mol % loadings on a 2 g scale of H(3) B ⋅ NMeH(2) to give polyaminoborane [H(2) BNMeH](n) [M(n) =30,900 g/mol, Ð=1.8] that can be purified to a low residual [Rh] (6 μg/g). Addition of Na[N(SiMe(3) )(2) ] to [H(2) BNMeH](n) results in selective depolymerization to form the eee-isomer of N,N,N-trimethylcyclotriborazane [H(2) BNMeH](3) : the chemical repurposing of a main-group polymer.