Stoichiometry controlled syntheses of cyanide-bound iron(II) and iron(III) complexes and their X-ray crystal structures

Two new meridionally positioned tricyanide building blocks consisting of low-spin iron(III), [(NBu4)[Fe(pzcq)(CN)(3)]center dot 1 center dot 5H(2)O (1), and low-spin iron(II), [PPH4](2)[Fe(pzcq)(CN)(3)]center dot 6H(2)O (2) [Hpzcq = 8-(pyrazine-2-carboxamido)quinoline], reported. X-Ray crystal structures reveal that, in both the complexes, Fe center is comprised of three C atoms from CN- ligands and three N atoms from the tridentate pzcq ligand in meridional fashion. It is worth noting that by simple variation of stoichiometric amounts of KCN both of the complexes could be produced from the same starting material. KCN not only binds to the metal center but also able to reduce iron(III) to iron(II) in 2.