μ‐Nitridodiiron Complexes with Asymmetric [FeIVN‐FeIII]⁴⁺ and Symmetric [FeIVNFeIV]⁵⁺ Structural Elements

Very strong antiferromagnetic coupling exists between the Fe centers in the N-bridged complexes 1 and 2. In 1 (shown on the right), which contains a symmetrical [FeIV = N = FeIV] unit, this results in an S = 0 ground state, while in 2, which has an unsymmetrical FeIII–N = FeIV bridge, it leads to an S = 3/2 ground state. Compound 2 forms in the photolysis of [FeIII(cat)N3] and can be oxidized with Br2 to give 1. L = trimethyltriazacyclononane, cat = tetrachlorocatecholate(2−).