Cyanide binding to iron in a highly distorted porphyrin macrocycle: Synthesis and structure of low-spin Fe(II) dicyano porphyrin

Dark brown crystals of [K(18-crown-6)(H2O)2]2[FeII(tn-OEP)(CN)2] are grown by slow diffusion of cyclohexane into the THF solutions of the molecule generated via auto reduction of [FeIII(tn-OEP)Cl] in the presence of KCN and 18-crown-6 at room temperature in air and structurally characterized. The complex represents the first structurally characterized dicyano Fe(II) porphyrins in a highly distorted and sterically crowded macocyclic environment. The metal iron is on the plane of the four porphyrinic nitrogens which are accompanied by the decrease of the saddle distortion with a clear and significant increase in ruffling.