Air-Stable Dinuclear Complexes of Four-Coordinate Zn^II and Ni^II Ions with a Radical Bridge: A Detailed Look at Redox Activity and Antiferromagnetic Coupling

Air-stable dinuclear complexes [(bmsab) Ni-II (tmsab) Ni-II (bmsab)](3-) and [(bmsab) Zn-II (tmsab) Zn-II (bmsab)](3-) (bmsab = bis (methanesulfoneamido) benzene, tmsab = tetra(methanesulfonamido)benzene) were prepared via a synthetic route based on heteroleptic precursor complexes. The new complexes combine a distorted tetrahedral coordination environment with an open-shell bridging ligand. The Zn-II species was subjected to a detailed investigation of the (spectro-)electrochemical processes. The Ni(II )species is a rare example of a complex that combines strong exchange coupling (J > 440 cm(-1)) with pronounced positive zero-field splitting (D = +72 cm(-1)). Combining SQUID magnetometry and (HF)EPR spectroscopy with ab initio calculations allowed for accurate quantification of the exchange interaction.