Hydrogen Bonds with BF(4)(-)Anion as a Proton Acceptor

The BF(4)(-)anion is characterised by weak Lewis base properties; it is usually classified as a non-coordinating anion. The searches through the Cambridge Structural Database (CSD) were performed and it was found that the BF(4)(-)anion often occurs in crystal structures and it is involved in numerous intermolecular interactions; hydrogen bonds are the majority of them. The hydrogen bonds involving the BF(4)(-)anion as a proton acceptor are closer to linearity with the increase of the strength of interaction that is in line with the tendency known for other hydrogen bonds. However, even for short contacts between the proton and the Lewis base centre, slight deviations from linearity occur. The MP2/aug-cc-pVTZ calculations on the BF4- horizontal ellipsis HCN complex and on the BF4- horizontal ellipsis (HCN)(4)cluster were also carried out to characterise corresponding C-H horizontal ellipsis F hydrogen bonds; such interactions often occur in crystal structures.