DFT investigation on dihydrogen-bonded amine-borane complexes

Abstract

The DFT method has been employed in the exploration on dihydrogen-bonded amine-borane complexes, with a special emphasis on the dimerization and substituent group effect. Stable dihydrogen bonded complexes can be generated from these amine-borane monomers with the appearance of NH(δ+)…H(δ-)B interactions. The binding energy decreases gradually with the increase of the steric effect of the substituents. The substituent group number mainly varies the C-N bond length. The dimerization generates close H…H and influences predominantly the N-B distance. The effect of dimerization on IR and vibrational circular dichroism (VCD) spectra is stronger than that of the number of substituent groups, which leads to distinct NBO charge variation on α-C. Both the substituent group number and dimerization enhance the chemical shift difference between hydrogen atoms covalently bonded to N and B, Δδ H-H, which can be hired as an index for structural determination. It is proposed that amine-borane complexes with more substituent groups in higher degree of polymerization are potentially interesting materials for hydrogen storage. Graphical Abstract Both the number of substituent group and dimerization enhance the chemical shift difference of hydrogen atoms covalently bonded on N and B, Δδ H-H, which can be employed as an index for the structural determination.

High‐Level Electron Correlation of the Indirect Nuclear Spin‐Spin Coupling Constants in Some Small Diboranes and Lithium‐Doped Diboranes

“…[14][15][16] In addition to the non-conventional hydrogen bonds boron can exhibit, the fundamental role for supramolecular synthesis that boron plays continuously reinforces its study. [17][18][19] For example, diborane(4) or B 2 H 4 has been investigated linked to some proton donors, [20] and was found that there is a region with a high concentration of electron density located near and along the BÀ B bond, on the opposite side of this bond relative to the bridging H atoms. Thus, the site serves as an electron-donor to electrophiles, resulting in hydrogenbonded complexes of between 2 to 27 kJ/mol for the few studied complexes.…”