Theoretical study of gas-phase acid-base equilibria

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Proton transfer reactions of hydrazine-boranes

International audienceHydrazine-borane and hydrazine-diborane contain respectively 15.4 and 16.9 wt% of hydrogen and are potential materials for hydrogen storage. In this work we present the gas-phase complexation energies, acidities and basicities of hydrazine-borane and hydrazine-bisborane calculated at MP2/6-311+G(d,p) level. We also report the release of dihydrogen from both protonated complexes (Ghydrazine-borane = –20.9 kcal/mol and Ghydrazine-bisborane = –27.2 kcal/mol) which is much more exergonic than from analogues amine-boranes. The addition of the first BH3 to the hydrazine releases 17.1 kcal/mol and the second addition releases 15.8 kcal/mol. The attachment of BH3 also increases the N-H acidity of hydrazine by 46.3 kcal/mol. It was found that the B-H deprotonation leads to intramolecular rearrangement. The basicity values for hydrazine-borane and –bisborane are 180 and 172.8 kcal/mol respectively. For both complexes the protonation centres are located at the boron moiety. The protonated structure of hydrazine-bisborane is cyclic and can be described as H2 captured between a negatively charged B-H hydrogen and positive boron (B-H••H2••B). Atoms in Molecules analysis is used to investigate bond paths in concerning structures

Proton and Lithium Cation Binding to Some β-Dicarbonyl Compounds. A Theoretical Study

DFT B3LYP/6-311+G** calculations were performed to study the proton and lithium cation binding to the acetylacetone, hexafluoroacetylacetone, diacetamide, and hexafluorodiacetamide. It was shown that the most stable Li+ adduct always corresponds to cyclic complex based on the trans, trans-keto form of the base. The product of protonation was found to be similar trans, trans-keto form based cyclic structure in case of diacetamide and hexafluorodiacetamide, while for acetylacetone and hexafluoroacetylacetone the protonation simply involves the addition of proton to (free) carbonyl oxygen in already cyclic enol form of the base with possible rotation of O−H bond