Molecular Insights on the Dihydrogen Bond Properties of Metal Borohydride Complexes upon Ammoniation

The dihydrogen bond (DHB) that exists between BH center dot center dot center dot HN containing systems is known for the improved thermodynamic properties of complex hydrides. This study explores the stability and electronic properties of dihydrogen bonds (H delta-center dot center dot center dot H delta+) that exist between the protic hydrogen, H delta+ in NH3 and hydridic hydrogen, H delta- of BH4 in AMgB center dot center dot center dot MB and AMgB center dot center dot center dot AMB complexes (where M = Li, Na, K, Mg and Zn; and A = Amino group) using second order Moller-Plesset perturbation theory (MP2). The effect of metals and ammoniation in varying the nature of the DHB was revealed in quantum theory of atoms in molecule (QTAIM) analysis with the identification of non-covalent interactions. The calculated values of interaction energies were correlated well with the topological results. Furthermore, energy decomposition analysis (EDA), interaction energy and Bader charge analysis were calculated in order to interpret the role of non-bonded interaction on decomposition process. The calculated structural, QTAIM and EDA analysis reveal the presence of non bonded interaction in all the complexes. Overall analysis of the study reported that the process of adding amine group in alkali metal borohydrides increases charge distribution around the dispersion interaction which plays a vital role in hydrogen evolution process.

Automated summary

This study investigated the stability and electronic properties of dihydrogen bonds between Hδ+ in NH3 and Hδ- in BH4 in various metal and ammoniated complexes. Analysis revealed the presence of non-covalent interactions and the role of dispersion interactions in the hydrogen evolution process. Overall, adding amine groups to alkali metal borohydrides increases charge distribution around the dispersion interaction, influencing hydrogen evolution.