On the possible solvation of tetraalkyl-ammonium cations and tetraphenyl-boron anions by water

Evidence of the extent of hydration of halide ions in aqueous solutions is discussed, and it is concluded that a primary solvation number of ca. 6 is correct. A recent suggestion that two different ways of describing this interaction, namely the "hydration number" ca. 2-3, and the "coordination number" ca. 6, does not seem to be desirable. It is suggested that neither R4N+ nor BPh4- ions are actively solvated in water. Instead, the vibrational spectral changes often associated with these ions are interpreted in terms of changes in the concentration of free O-H groups. These changes are caused by active solvation of the gegen ions.