Solid‐State Structures of Primary Long‐Chain Alkylamine Borane Adducts – Synthesis, Properties and Computational Analysis

Abstract

Two new members of the amine boranes family are hexadecylamine borane C16H33NH2BH3 (C16AB) and octadecylamine borane C18H35NH2BH3 (C18AB). They are easily synthesized by reaction of the corresponding amines with borane dimethyl sulfide. Both are white solids; they are crystalline and isostructural (monoclinic, s.g. P21/a (No. 14)). Their successful synthesis has been verified by molecular (FTIR, Raman, NMR) and structural analyses as well as computational calculations (e. g. Mulliken charges). These analyses have also pointed out the existence of dihydrogen bonds between Hδ+ of NH2 of one molecule and Hδ− of BH3 of another molecule. The thermal stability of C16AB and C18AB was studied. Both solids melts at 70–80 °C; between 100 and ca. 210 °C they dehydrogenate while releasing 1.1‐1.4 wt% of pure H2; and, above 210 °C, they decompose in high extent. All of these findings may open the way to future works on molecular self‐assembly, synthesis of advanced materials and hydrogen storage. This is discussed hereafter.

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

“…In a first stage, we have been synthesizing and acutely characterizing new ABAs. Recently, we released the results concerning eight alkylamine borane adducts C n H 2n+1 NH 2 BH 3 ( n = 4, 6, 8, 10, 12, 14, 16 or 18) [ 31 , 32 ]. All have shown higher melting points (by 20–40 °C) than the parent amine C n H 2n+1 NH 2 , and such a gain of stability has been explained by the existence of DHBs.…”

Nanostructured Carbon-Doped BN for CO2 Capture Applications

“…In order to pursue the structuration studies of AB leading to BN materials, alkyl amine borane adducts (ABAs) were used as soft templating agents. We have previously described the synthesis of primary alkylamine borane adducts, C x H 2x+1 NH 2 BH 3 (CxAB), with butyl, hexyl, octyl, decyl, dodecyl, tetradecyl, hexadecyl and octadecyl chains (x = 4, 6, 8, 10, 12, 14, 16 and 18, respectively) [22,23]. These ABAs were fully characterized, especially from a crystallographic point of view, in order to scrutinize the occurrence of dihydrogen H δ+ •••H δ− bonds for the heads of the solid ABAs.…”