Synthesis and Characterization of an Iron Complex Bearing a Cyclic Tetra-N-heterocyclic Carbene Ligand: An Artifical Heme Analogue?

An
iron­(II) complex with a cyclic tetradentate ligand containing four
N-heterocyclic carbenes was synthesized and characterized by means
of NMR and IR spectroscopies, as well as by single-crystal X-ray structure
analysis. The iron center exhibits an octahedral coordination geometry
with two acetonitrile ligands in axial positions, showing structural
analogies with porphyrine-ligated iron complexes. The acetonitrile
ligands can readily be substituted by other ligands, for instance,
dimethyl sulfoxide, carbon monoxide, and nitric oxide. Cyclic voltammetry
was used to examine the electronic properties of the synthesized compounds.