Synthesis and Characterization of (R)-N-1-Cyclohexylethylamine Borane

A new solid amine borane is reported here. The reaction of (R)-(-)-1-cyclohexylethylamine (a liquid at room temperature) with borane dimethylsulfide yields crystals of pure (R)-N-1-cyclohexylethylamine borane C6H11CH(CH3)NH2BH3 (CHEAB). The successful synthesis was confirmed by molecular analyses (FTIR, Raman and NMR). The crystals are in the form of millimeter-sized translucent sticks, which allowed determining that CHEAB crystallizes in the orthorhombic system, the space group being P212121. All of the characterization results, together with DFT calculations, strongly suggest the occurrence of intermolecular dihydrogen bonds between antiparallel NH2BH3 groups that are in a trimeric configuration. (R)-N-1-cyclohexylethylamine borane C6H11CH(CH3)NH2BH3 (CHEAB) is a new solid amine borane that forms as millimeter-sized translucent stick-like crystals (orthorhombic; s.g. P212121) owing to the occurrence of intermolecular dihydrogen bonds between antiparallel NH2BH3 groups. Pure CHEAB decomposes under heating and is not suitable for hydrogen storage, but it may have potential as a precursor of polymers and/or carbon-doped boron nitride.image