Synthesis and crystal structure of two manganese-based 12-metallacrown-4 complexes: Na ₂(3-chloro-benzoate) ₂[12-MC _{Mn(III)N(shi)}-4](DMF) ₆ and MnNa(3-chloro-benzoate) ₃[12-MC _{Mn(III)N(shi)}-4](DMF)(H ₂ O) ₄·4DMF·0.72H ₂ O

Similar synthetic schemes yield two different metallacrown (MC) complexes: bis-(μ-3-chloro-benzoato)hexa-kis-(di-methyl-formamide)-tetra-kis-(μ₄-N,2-dioxido-benzene-1-carboximidato)tetra-manganese(III)disodium(I), [Mn₄Na₂(C₇H₄ClO₂)₂(C₇H₄NO₃)₄(C₃H₇NO)₆] or Na₂(3-chloro-benzoate)₂[12-MC_{Mn(III)N(shi)}-4](DMF)₆, 1, and tetra-μ-aqua-tris-(μ-3-chloro-benzoato)(di-methyl-formamide)-tetra-kis-(μ₄-N,2-dioxido-benzene-1-carboximidato)penta-manganese(III)sodi-um(I) di-methyl-formamide tetra-solvate 0.72-hydrate, [Mn₅Na(C₇H₄ClO₂)₃(C₇H₄NO₃)₄(C₃H₇NO)(H₂O)₄]·4C₃H₇NO·0.718H₂O or MnNa(3-chloro-benzo-ate)₃[12-MC_{Mn(III)N(shi)}-4](DMF)(H₂O)₄·4DMF·0.72H₂O, 2, where shi^3- is salicyl-hydrox-imate and DMF is N,N-di-methyl-formamide. Both complexes have the same framework consisting of four Mn^III ions in the MC ring and four shi^3- ligands, resulting in an overall square-shaped mol-ecule. The Mn^III ions are either five- or six-coordinate with elongated bond lengths in the apical or axial direction, respectively. The structure of 1 is nearly planar, and the MC binds two Na⁺ ions on opposite faces of the MC central cavity. The 3-chloro-benzoate anions also bind on opposite faces of the MC and form bridges between the central Na⁺ ions and the ring Mn^III ions. For 1 the metallacrown mol-ecule, except for the central Na⁺ ion, exhibits whole mol-ecule disorder over two sets of sites. Both moieties are centrosymmetric and are related to each other by a pseudo-mirror operation with opposite sense of rotation around the Na⋯Na axis. The occupancy ratio of the main disorder of the metallacrown mol-ecules and 3-chloro-benzoate anions refined to 0.9276 (9):0.0724 (9). The structure of 2 is slightly domed, and the MC binds both an Mn^II ion and an Na⁺ ion in the MC central cavity. The Mn^II ion is located on the convex side of the MC, while the Na⁺ ion binds to the concave side. Complex 2 represents the first instance of a [12-MC_{Mn(III)N(shi)}-4] mol-ecule binding both 3d transition metal and alkali metal ions in the central cavity. In addition, three 3-chloro-benzoate anions bind on the convex side of the MC and connect the Mn^II ion to three of the ring Mn^III ions.

Keywords: crystal structure; manganese complex; metallacrown; salicyl­hydroximate.