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

A new bimetallic platform comprising a six-coordinate Fe(ONO)(2) unit bound to an (ONO)M (M = Fe, Zn) has been discovered ((ONO(cat))H(3) = bis(3,5-di-tert-butyl-2-phenol)amine). Reaction of Fe(ONO)(2) with either (ONO(cat))Fe(py)(3) or with (ONO(q))FeCl(2) under reducing conditions led to the formation of the bimetallic complex Fe(2)(ONO)(3), which includes unique five- and six-coordinate iron centers. Similarly, the reaction of Fe(ONO)(2) with the new synthon (ONO(sq)˙)Zn(py)(2) led to the formation of the heterobimetallic complex FeZn(ONO)(3), 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)(3) are consistent with a ground state S = 3/2 spin system, generated from a high-spin iron(ii) center that is antiferromagnetically coupled to a single (ONO(sq)˙)(2–) radical ligand. In the case of Fe(2)(ONO)(3), the magnetic data revealed a ground state S = 7/2 spin system arising from the interactions of one high-spin iron(ii) center, one high-spin iron(iii) center, and two (ONO(sq)˙)(2–) radical ligands.