Quantum chemical and experimental insights for the ionic liquid facilitated thermal dehydrogenation of ethylene diamine bisborane

Abstract

The current work reports the judicial selection and subsequent dehydrogenation reaction with ionic liquid (IL) facilitated ethylene diamine bisborane (EDAB). Quantum chemical based COSMO-SAC (COnductor like Screening MOdel Segment Activity Coefficient) model was initially used to screen the ILs as available from Sigma Aldrich. LUMO-HOMO calculation was then performed to analyze the stability of EDAB/IL complexes. The molecular modeling studies converged on the two ILs, namely 1-ethyl-3-methyl imidazolium acetate ([EMIM][OAc]) and 1-butyl-3-methyl imidazolium acetate ([BMIM][OAc]), which were subsequently chosen for the dehydrogenation experiments. The thermal dehydrogenation of EDAB was carried out at 95 C and 105 C under vacuum so as to prevent generation of oxygen moieties. A total of 3.96 and 3.52 equivalents of hydrogen were released from the desorption of EDAB/[BMIM][OAc] and EDAB/[EMIM][OAc], respectively, at 105 C. The purity of released gas was confirmed by gas chromatographic analysis, while the catalytic activity of ILs was confirmed by 1 H NMR characterization of pure EDAB, ILs and EDAB/IL complexes both before and after the reaction. 11 B NMR analysis confirms the presence of trigonal boron (sp 2 ) BH 2 group as the only hydrogen containing boron moiety in dehydrogenated EDAB. Further, the two-stage release mechanism of EDAB was also verified by thermogravimetric analysis. High resolution mass spectrometry was able to detect the mass of cyclic repeat units in the polymeric chain containing an sp 2 BH 2 group. † Electronic supplementary information (ESI) available: The COSMO-SAC parameters and the sigma proles of EDAB, imidazolium cations and acetate anions. Further it also depicts the HOMO-LUMO energy gap of EDAB, [EMIM] [OAc] and [BMIM][OAc]. SeeFig. 8 Plot for 11 B NMR. (a) EDAB/[BMIM][OAc] before reaction, (b) EDAB/[BMIM][OAc] after reaction.This journal is

Effect of thiocyanate‐based ionic liquids on the dehydrogenation of amine boranes: Experimental and molecular modeling studies

“…Palladium and ruthenium nanoparticle‐supported hydrophobic IL‐based scaffolds were used for this work. Banerjee et al employed QC‐based screening to screen acetate‐based ILs from a pool of 205 ILs. In a subsequent report, Banerjee et al employed reactive force field simulation to elucidate the EDAB/IL desorption mechanism.…”

“…The dehydrogenation reaction was then performed at 105°C. The reason for selection of this temperature is due to the fact that approximate release of 4 equivalent of hydrogen was obtained from EDAB/IL system at 105°C . Further, Himmelberger et al reported an absence of induction period for dehydrogenation of AB/IL system at 105°C.…”

“…The potential role of ILs as solvent and catalysis can thus be tuned for dehydrogenation of amine boranes. The first reported work of IL‐facilitated dehydrogenation of AB was carried out by Bluhm et al, and the mechanistic investigation was given by Himmelberger et al Dehydrogenation of EDAB and other carbon derivatives of amine boranes using IL has been reported in quite a few of scientific reports . However, most of these works preferred to exploit the amine boranes in imidazolium cation containing ILs, which are acidic in nature.…”

Ionic Liquid Facilitated Dehydrogenation of tert-Butylamine Borane

“…It is evident that imidazolium IL facilitates a faster and higher amount of hydrogen release, in line with the similar trend for IL-assisted dehydrogenation of EDAB. 16,18 Upon heating, the TBAB/[BMIM][OAc] system instantly releases hydrogen. A single equivalent of hydrogen is seen to release within 30 min of dehydrogenation, and after 180 min, the release becomes negligible.…”

“…Sahler et al 15 also reported the use of imidazolium IL, which lowers the activation energy and enhances the yield of hydrogen for the dehydrogenation of ethylene diamine bisborane (EDAB). Banerjee et al 16 recently reported a 3.96 equiv yield of H 2 at 105 °C from EDAB using 1-butyl-3-methylimidazolium acetate ([BMIM]-[OAc]) IL. In combination with basic anions, imidazolium cations exert a strong effect on the yield of hydrogen.…”