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.