Deformation Densities In Hydrogen Bonds To Aromatic Pi Systems. Cameron, T.S, Kwiatkowski, W., Robertson, K.N., and Knop, O., Department of Chemistry, Dalhousie, University, Halifax, NS, Canada B3H 4J3.

The water-insoluble, crystalline ammonium tetraphenylborate NH₄BPh₄, contains N_H...phenyl interactions which have been described as N_H...pi(phenyl) hydrogen bonds [1,2]. Such bonds have also been found to exist in the overwhelming majority of the over 150 analogous, also water-insoluble organoammonium tetraphenylborates that we have investigated to date [3-6]. This N_H...phenyl interaction has now been examined by high- resolution, low-temperature X-ray diffraction methods and the deformation densities have been determined for the tetraphenylborates of the ammonium, dabco⁺, C(NH₂)₃⁺ (guanidinium), and (NH₂)₂CNC(NH₂)₂⁺ (biguanidinium) cations. Details of this work and examples of the deformation densities will be shown.

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[5] O. Knop, T.S. Cameron, P.K. Bakshi, A. Linden, S.P. Roe, Can. J. Chem., 1994, 72, 1870.

[6] P.K. Bakshi, T.S. Cameron, O. Knop, Can. J. Chem., 1996, 74, 201.