Anion–π interaction with alkenes: persistent complexes <i>vs.</i> irreversible reactions of anions with tetracyanoethylene

Anion–π complexes with the electron-deficient alkene, tetracyanoethylene, are similar to that with aromatic and p -benzoquinone π-acceptors, but their persistence is delimited by the 1e-donating strength and nucleophilicity of anions.