A MP2(full) and CCSD(T) theoretical investigation on the dihydrogen-bonded interactions between HNa and RBBH (R = F, Cl, H, CN, NC and CO)

As a follow-up to our study on the interaction between HBBH and HM, in this paper, the substituent effect on the dihydrogen-bonded interaction between HNa and RBBH (R = F, Cl, H, NC, CN or CO) is investigated using the MP2(full) and CCSD(T) methods with the 6-311++G(3df,2p) and aug-cc-pVTZ basis sets. The binding energies follow the order of NCBBH⋯HNa > CNBBH⋯HNa > HBBH⋯HNa > ClBBH⋯HNa > FBBH⋯HNa, and correlate with the H⋯H distance, the decrease of the HNa bond length and the charge density at the H⋯H bond critical point except for OCBBH⋯HNa. The analyses of the natural bond orbital (NBO) and atoms in molecules (AIM) show that, the substituent CN or NC increases the positive charge in the B1 atom by means of the π–π conjugative effect, leading to an increase of the acidity of the H3 atom and the strengthened dihydrogen-bonded interaction in comparison with HBBH⋯HNa. However, the substituent effect of F or Cl on the dihydrogen-bonded interaction is not obvious. The analyses of reaction path of the H2 elimination, NBO and AIM confirm that the loss of H2 might occur from the neutral dihydrogen-bonded complex OCBBH⋯HNa.