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

We report the synthesis and characterization of three dinuclear 3 d 3 d ' complexes, CuCu ( [ C u 2 I I L ( N O 3 ) 2 ] ), MnMn ( [ M n 2 I I L ( M e O H ) 2 ( N O 3 ) 2 ] ), and CuMn ([Cu II Mn II L (NO 3 ) 2 ]), that utilize the ligand, H 2 L (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 .