Varying the secondary coordination sphere: synthesis of cobalt and iron complexes of a tripodal ligand featuring two hydrogen-bond donors or acceptors

In order to further understand the role of the secondary coordination sphere in biomimetic systems, a series of cobalt(II) and iron(II) complexes bearing the non-heme bis(5-cyclohexyliminopyrrol-2-ylmethyl)-2-pyridylmethylamine (^PyN(pi^Cy)₂) ligand were synthesized. This platform, based on the tris(5-cyclohexylimino-pyrrol-2-ylmethyl)amine (N(pi^Cy)₃) platform, reduces the number of possible hydrogen-bonding interactions from three (in N(pi^Cy)₃) to two, while maintaining the ability of the ligand to datively coordinate to a metal center. The secondary coordination spheres of the family of dative and anionic cobalt(II) and iron(II) complexes were characterized in the solid-state using X-ray crystallography and IR spectroscopy. Moreover, oxidation of an iron(II) complex was explored to compare its reactivity to that of the analogous iron(II) complex of the N(pi^Cy)₃ platform.