Further study of the reaction of Fe2+ with CN-: synthesis and characterization of cis and trans [FeII,III(CN)4L2]n- complexes

The reaction of Fe2+ with CN-, which was first performed in 1704, has been used to synthesize a new series of basic FeII,III(CN)4L2]n- complexes, where L is a monodentate ligand. trans-Na2FeII(CN)4(DMSO)2] and cis-NEt4]2FeII(CN)4(pyridine)2] are synthesized by the direct reaction of FeCl2 with 4 equiv of CN- in DMSO or pyridine. Air oxidation of the latter compound gives cis-NEt4]FeIII(CN)4(pyridine)2]. The non-cyanide ligands in these complexes undergo facile ligand exchange reactions with solvent. Reaction of cis-NEt4]2FeII(CN)4(pyridine)2] with CO at room temperature gives trans-NEt4]2FeII(CN)4(pyridine)(CO)].