Infrared spectral studies of ion association in nonaqueous solutions of cyanide salts with consequences for their nucleophilic reactivity

An infrared spectrometric study of alkali metal and tetraphenylarsonium cyanide (As⁴CN) solutions in DMSO or DMF shows that even for concentrations of 0.1M a large proportion of the ions are associated. The order of basicity established through methanol (OH) frequency shifts is CN^–>Cl^–>Br^–. Addition of common ions or cyclic polyether to these solutions, as well as correlations between the (CN^–) frequencies and those of the (CN) bands of CH₃CN bonded to the same cations, suggests assignments of the observed bands to solvated contact ion pairs M⁺ CN^–, triple ions M⁺ CN^– M⁺, and aggregates (M⁺ CN)_n^–. The nucleophilic reactivity of these salts is related to the structure of these solutions.This article is taken in part from the thesis of A. Loupy, University Paris-Sud Orsay, April 9, 1975, CNRS thesis order No. AO 10102.