Synthesis: Molecular Structure, Thermal-Calorimetric and Computational Analyses, of Three New Amine Borane Adducts

Cyclopropylamine borane C(3)H(5)NH(2)BH(3) (C3AB), 2-ethyl-1-hexylamine borane CH(3)(CH(2))(3)CH(C(2)H(5))CH(2)NH(2)BH(3) (C2C6AB) and didodecylamine borane (C(12)H(25))(2)NHBH(3) ((C12)2AB) are three new amine borane adducts (ABAs). They are synthesized by reaction of the corresponding amines with a borane complex, the reaction being exothermic as shown by Calvet calorimetry. The successful synthesis of each has been demonstrated by FTIR, Raman and NMR. For instance, the (11)B NMR spectra show the presence of signals typical of the NBH(3) environment, thereby implying the formation of B–N bonds. The occurrence of dihydrogen bonds (DHBs) for each of the ABAs has been highlighted by DSC and FTIR, and supported by DFT calculations (via the Mulliken charges for example). When heated, the three ABAs behave differently: C3AB and C2C6AB decompose from 68 to 100 °C whereas (C12)2AB is relatively stable up to 173 °C. That means that these ABAs are not appropriate as hydrogen carriers, but the ‘most’ stable (C12)2AB could open perspectives for the synthesis of advanced materials.