Interaction of metal cations with alkylnitriles in the gas phase: solvation of metal ions by the hydrocarbon chain.

Relative affinity measurements of monovalent metal ions (M = Li(+), Na(+), Cu(+)and Ag(+)) toward aliphatic nitriles have been performed using the kinetic method by dissociation of metal bound dimer ions of the type R1C≡N-M(+)-N≡CR(2). It is found, particularly for Cu(+) and Ag(+), that the affinity towards nitriles having long chains (>C(6)) is markedly enhanced. This is attributed to a bidentate interaction of the metal ion with the nitrile moiety and the aliphatic chain. Theoretical calculations on the copper complexes show that these bidentate structures enjoy about 30% greater copper ion affinities compared to their linear counterparts. Such aliphatic interactions also play a major role in the dissociation chemistry of copper bound tetramers of the kind (RC≡N)(4)Cu(2+∙) where the long aliphatic chain R curls around the copper ion to facilitate electron transfer or a redox reaction to produce (RC≡N)(2)Cu(+) + RC≡N(+∙) + RC≡N.