Some measures for mediating the strengths of halogen bonds with the B–B bond in diborane(4) as an unconventional halogen acceptor

A series of halogen-bonded complexes with diborane(4) 1 and its derivatives (Li 2, methyl 3, CN 4) as the halogen acceptors as well as with XCN, XCCH, XCF3, XF (X = Cl, Br, I) as the halogen donors have been investigated by means of quantum chemical calculations at the MP2/aug-cc-pVTZ level. The result shows that the BB bond is a good electron donor in halogen bonding, particularly for the halogen donor XF. Interestingly, for the halogen donor XF, the halogen bond becomes stronger in order of IF < BrF < ClF. It is found that the addition of electron-donating substituents greatly strengthens the halogen bonding interaction to the point where it exceeds that of the majority of H-bonds. When the N atom in 2-BrCN is combined with another interaction, its strength has a further increase due to the cooperative effect. This study combines the boron compounds with halogen bonds and would be significant for expanding their applied fields. © 2013 Wiley Periodicals, Inc.