Bimetallic iron-iron and iron-zinc complexes of the redox-active ONO pincer ligand.

A new bimetallic platform comprising a six-coordinate Fe(ONO) unit bound to an (ONO)M (M = Fe, Zn) has been discovered ((ONO)H = bis(3,5-di--butyl-2-phenol)amine). Reaction of Fe(ONO) with either (ONO)Fe(py) or with (ONO)FeCl under reducing conditions led to the formation of the bimetallic complex Fe(ONO), which includes unique five- and six-coordinate iron centers. Similarly, the reaction of Fe(ONO) with the new synthon (ONO˙)Zn(py) led to the formation of the heterobimetallic complex FeZn(ONO), with a six-coordinate iron center and a five-coordinate zinc center. Both bimetallic complexes were characterized by single-crystal X-ray diffraction studies, solid-state magnetic measurements, and multiple spectroscopic techniques. The magnetic data for FeZn(ONO) are consistent with a ground state = 3/2 spin system, generated from a high-spin iron(ii) center that is antiferromagnetically coupled to a single (ONO˙) radical ligand. In the case of Fe(ONO), the magnetic data revealed a ground state = 7/2 spin system arising from the interactions of one high-spin iron(ii) center, one high-spin iron(iii) center, and two (ONO˙) radical ligands.