Ambident Reactivity of the Cyanide Ion: A Failure of the HSAB Principle

Diffusion or activation control: Free CN− ions are generally alkylated at carbon (see picture). N‐attack is only observable in diffusion controlled reactions with carbocations. Since isonitrile formation in reactions with [Ag(CN)2]− is due to the change of the nucleophile, the explanation of these regioselectivities by the hard and soft acids and bases principle has to be abandoned.