Synthesis and crystal structure of two manganese-based 12-metallacrown-4 complexes: Na₂(3-chlorobenzoate)₂[12-MC_{Mn(III)N(shi)}-4](DMF)₆ and MnNa(3-chlorobenzoate)₃[12-MC_{Mn(III)N(shi)}-4](DMF)(H₂O)₄·4DMF·0.72H₂O

Abstract

Similar synthetic schemes yield two different metallacrown (MC) complexes: bis(μ-3-chlorobenzoato)hexakis(dimethylformamide)tetrakis(μ4-N,2-dioxidobenzene-1-carboximidato)tetramanganese(III)disodium(I), [Mn4Na2(C7H4ClO2)2(C7H4NO3)4(C3H7NO)6] or Na2(3-chlorobenzoate)2[12-MCMn(III)N(shi)-4](DMF)6, 1, and tetra-μ-aqua-tris(μ-3-chlorobenzoato)(dimethylformamide)tetrakis(μ4-N,2-dioxidobenzene-1-carboximidato)pentamanganese(III)sodium(I) dimethylformamide tetrasolvate 0.72-hydrate, [Mn5Na(C7H4ClO2)3(C7H4NO3)4(C3H7NO)(H2O)4]·4C3H7NO·0.718H2O or MnNa(3-chlorobenzoate)3[12-MCMn(III)N(shi)-4](DMF)(H2O)4·4DMF·0.72H2O, 2, where shi3− is salicylhydroximate and DMF is N,N-dimethylformamide. Both complexes have the same framework consisting of four MnIII ions in the MC ring and four shi3− ligands, resulting in an overall square-shaped molecule. The MnIII 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-chlorobenzoate anions also bind on opposite faces of the MC and form bridges between the central Na+ ions and the ring MnIII ions. For 1 the metallacrown molecule, except for the central Na+ ion, exhibits whole molecule 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 molecules and 3-chlorobenzoate anions refined to 0.9276 (9):0.0724 (9). The structure of 2 is slightly domed, and the MC binds both an MnII ion and an Na+ ion in the MC central cavity. The MnII 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-MCMn(III)N(shi)-4] molecule binding both 3d transition metal and alkali metal ions in the central cavity. In addition, three 3-chlorobenzoate anions bind on the convex side of the MC and connect the MnII ion to three of the ring MnIII ions.