Against the Norm: Non Irving–Williams Transmetalation in Transition Metal Dimers

We report the synthesis and characterization of three dinuclear 3d3d' complexes, CuCu ([Cu2IIL(NO3)2]), MnMn ([Mn2IIL(MeOH)2(NO3)2]), and CuMn ([Cu^IIMn^IIL(NO₃)₂]), that utilize the ligand, H₂L (6,6'-dimethoxy-2,2'-[(1,3-propylene)dioxybis(nitrilomethylidyne)]diphenol). The relative stabilities of these complexes were investigated using experimental and computational techniques, revealing a non-Irving-Williams transmetalation, whereby a Mn^II ion can displace a Cu^II ion from its binding pocket in CuCu to yield the more stable CuMn complex. Magnetic characterization of the reported complexes revealed an unexpected ferromagnetic coupling between the two Cu^II ions of CuCu with J = +63.0 cm^-1.