Hydrogen bonding. Part 84. Infrared spectral evidence for three-center NHF bonds in a variety of tertiary amine-hydrogen fluoride compounds

N,N-dimethyl-1-adamantamine-hydrogen fluoride (2MAAHF) was previously shown by infrared spectral comparison to known compounds, ab initio molecular orbital treatment, and FT-NMR studies to contain a covalent three-center NHF bond which does not dissociate in aqueous solution. We have now examined a number of 1:1 hydrogen fluoride compounds of other tertiary amines, including monocyclic, bicyclic, aromatic, and trialkyl examples. All give the distinctive infrared absorptions of NHF bonds similar to those of 2MAAHF. Since these compounds were isolated from—and may well be stable in—aqueous solution, such species could play a role in the interaction of hydrogen fluoride or fluoride ion with biological material. q 2005 Elsevier B.V. All rights reserved.