Non-Covalent Interactions in Hydrogen Storage Materials LiN(CH3)2BH3 and KN(CH3)2BH3

In the present work, an in-depth, qualitative and quantitative description of non-covalent interactions in the hydrogen storage materials LiN(CH3)(2)BH3 and KN(CH3)(2)BH3 was performed by means of the charge and energy decomposition method (ETS-NOCV) as well as the Interacting Quantum Atoms (IQA) approach. It was determined that both crystals are stabilized by electrostatically dominated intra- and intermolecular M...H-B interactions (M = Li, K). For LiN(CH3)(2)BH3 the intramolecular charge transfer appeared (B-HLi) to be more pronounced compared with the corresponding intermolecular contribution. We clarified for the first time, based on the ETS-NOCV and IQA methods, that homopolar BH...HB interactions in LiN(CH3)(2)BH3 can be considered as destabilizing (due to the dominance of repulsion caused by negatively charged borane units), despite the fact that some charge delocalization within BH...HB contacts is enforced (which explains H...H bond critical points found from the QTAIM method). Interestingly, quite similar (to BH...HB) intermolecular homopolar dihydrogen bonds CH...HC appared to significantly stabilize both crystalsthe ETS-NOCV scheme allowed us to conclude that CH...HC interactions are dispersion dominated, however, the electrostatic and sigma/sigma*(C-H) charge transfer contributions are also important. These interactions appeared to be more pronounced in KN(CH3)(2)BH3 compared with LiN(CH3)(2)BH3.