Crystal structure of di-μ-chloroacetato-hexakis(dimethylformamide)tetrakis(μ-N,2-dioxidobenzene-1-carboximidato)tetramanganese(III)disodium dimethylformamide disolvate

The title compound consists of a macrocyclic ring with an MnIII—N—O repeat unit that occurs four times, producing a molecule with an overall square structure. Two Na+ ions are captured above and below the central cavity of the molecule.


Chemical context
Metallacrowns (MCs) are a family of macrocyclic inorganic complexes with structural and functional similarity to crown ethers (Mezei et al., 2007). As crown ethers are composed of a -[C-C-O] n -repeat unit, metallacrowns possess an -[M-N-O] n -repeat unit. While metallacrowns can selectively bind alkali metal ions in the central cavity similar to crown ethers, MCs have also found applications as singlemolecule magnets, antimicrobial agents, and building blocks for one-, two-, and three-dimensional solids (Mezei et al., 2007). The controllable synthesis of macrocyclic inorganic molecules is of importance if the properties of a molecule are to be tailored for a specific application. However, inorganic reactions can be unpredictable due to labile metal-ligand coordination bonds. In addition, the products of many inorganic reactions can be serendipitous in nature (Saalfrank et al., 2008). Thus, the ability to controllably substitute components of a molecular class allow for the fine-tuning of molecular properties.
The 12-MC Mn III N(shi) -4 class of molecules, with Mn III ions as the ring metal and salicylhydroximate (shi 3À ) ligands composing the MC framework, provide a rich opportunity to perform substitution reactions. These metallacrowns can bind a variety of metal ions in the central cavity such as Mn II , Li + , Na + , K + , Ca 2+ , and Ln III ions (Ln is a lanthanide) (Lah & Pecoraro, 1989, 1991Gibney et al., 1996;Kessissoglou et al., ISSN 1600-5368

Structural commentary
The title compound consists of the typical 12-MC Mn III N(shi) -4 framework with four Mn III -N-O repeating units producing an overall square-geometry molecule (Fig. 1). As in other disodium 12-MC Mn III N(shi) -4 complexes (Lah & Pecoraro, 1991;Gibney et al., 1996;Kessissoglou et al., 2002;Azar et al., 2014), an inversion center is located in the central MC cavity produced by the oxime oxygen atoms of the shi 3À ligands. In addition, two Na + ions are captured in the central cavity on opposite faces of the MC (Fig. 2). A chloroacetate anion bridges each Na + ion to a ring manganese ion. The entire molecule (metallacrown, chloroacetate counter-anions, and coordinating DMF molecules) is disordered over two sites with an occupancy ratio of 0.8783 (7):0.1217 (7) (complete refinement details are given below); thus, a description will only be given for the higher occupancy component. The metallacrown is nearly planar, but it can be considered to possess a stepped structure, i.e. the MC is ruffled (Fig. 2). Charge neutrality is maintained for the molecule by the presence of four Mn III and two Na + cations and four shi 3À and two chloroacetate anions. The oxidation state assignment of the ring Mn III ions is supported by the average bond lengths, bond-valence-sum (BVS) calculations, and the presence of elongated axial bond lengths expected for a high-spin d 4 electron configuration (Liu & Thorp, 1993 Molecular structure of Na 2 (O 2 CCH 2 Cl) 2  -4](DMF) 6 Á-2DMF (top view). The displacement ellipsoid plot is at the 50% probability level. Atom labels for all non-H atoms on one asymmetric unit of the 12-MC-4 framework and selected symmetry-equivalent atoms have been provided. For clarity, atom labels for the axial DMF and chloroacetate ligands have been omitted; those labels may be found in Fig. 2. H atoms and the lattice solvent molecules have been omitted for clarity. Color scheme: green Mn III , yellow Na + , purple chlorine, red oxygen, blue nitrogen, and gray carbon. [Symmetry code: (ii) Àx + 1, Ày, Àz + 1.]

Figure 2
Molecular structure of Na 2 (O 2 CCH 2 Cl) 2  -4](DMF) 6 Á-2DMF (side view). The stepped or ruffled character of the structure is emphasised in this view. Atom labels for all non-hydrogen atoms of the axial DMF and chloroacetate ligands on one asymmetric unit have been provided. See Fig. 1 for display details.
valence units (v.u.), and for Mn2 the average bond length is 1.96 Å and the BVS value is 2.98 v.u.
The coordination geometry about Mn1 is best described as a tetragonally distorted octahedron with the equatorial ligands comprised of an oxime nitrogen atom and a phenolate oxygen atom from one shi 3À ligand and an oxime oxygen atom and carbonyl oxygen atom from a second shi 3À ligand. The Jahn-Teller axis is completed by the carbonyl oxygen atoms of two trans DMF molecules (average Mn-O JT = 2.31 Å ). The carbonyl oxygen atom (O10) of one of the DMF molecules also serves as a one-atom bridge to the central Na + ion. For Mn2, the coordination geometry is best described as distorted square-pyramidal with a value of 0.05, where = 0 for ideal square-pyramidal geometry and = 1 for ideal trigonalbipyramidal geometry (Addison et al., 1984). The basal ligands are comprised of an oxime nitrogen atom and a phenolate oxygen atom from one shi 3À ligand and an oxime oxygen atom and a carbonyl oxygen atom from a second shi 3À ligand. The oxygen atom of a chloroacetate anion binds in the elongated apical direction [Mn2-O7: 2.1202 (15) Å ]. The chloroacetate forms a three-atom bridge to the central Na + ion. Each Na + ion is seven coordinate. The four oxime oxygen atoms of the MC cavity form a square face below the Na + ion, and three oxygen atoms form a triangular face above the ion. The three oxygen atoms are from the bridging chloroacetate anion, a carbonyl oxygen atom of the bridging DMF molecule, and a carbonyl oxygen atom of a terminal DMF molecule. Lastly two DMF molecules, which are related by the inversion center at (0.5, 0.0, 0.5), are located in the lattice and are disordered over two sites with different orientations with an occupancy ratio of 0.615 (5):0.385 (5).

Supramolecular features
No strong directional intermolecular interactions are observed between the Na 2 (O 2 CCH 2 Cl) 2  -4](DMF) 6 molecules, but a number of weak intramolecular and intermolecular C-HÁ Á ÁO interactions exist (Table 1). The intramolecular interactions exist between an oxygen atom of the bridging chloroacetate anion and a methyl carbon atom of a coordinating DMF molecule and a carbonyl carbon atom of another coordinating DMF molecule, and between the carbonyl oxygen atom of a shi 3À ligand and the methyl carbon atom of a coordinating DMF molecule (Fig. 3). The intermolecular interactions exist between the carbonyl oxygen atom of a lattice DMF molecule and the methyl carbon atoms of two different coordinating DMF molecules, between an oxygen atom of a chloroacetate and a carbonyl carbon atom of a lattice DMF molecule, between a carbonyl oxygen atom of a Symmetry codes: (i) Àx þ 1 2 ; y þ 1 2 ; Àz þ 1 2 ; (ii) Àx þ 1; Ày; Àz þ 1; (iii) Àx þ 1 2 ; y À 1 2 ; Àz þ 1 2 .

Figure 3
Intra-and intermolecular hydrogen bonding within the metallacrown itself and between the MC and the lattice DMF molecule. For clarity, only the H atoms (white) involved in the hydrogen bonding have been included and only the atoms involved in the hydrogen bonding have been labelled. See Fig. 1 for display details. [Symmetry code: (ii) Àx + 1, Ày, Àz + 1.]

Figure 4
Intermolecular hydrogen bonding between adjacent metallacrowns and between the MC and the lattice DMF molecule. For clarity, only the H atoms (white) involved in the hydrogen bonding have been included and only the atoms involved in the hydrogen bonding have been labelled. See Fig. 1 for display details. [Symmetry codes: (i) Àx + 1 2 , y + 1 2 , Àz + 1 2 ; (iii) Àx + 1 2 , y À 1 2 , Àz + 1 2 .] coordinating DMF molecule and a methyl carbon atom of a coordinating DMF molecule of an adjacent MC, and between a carbonyl oxygen atom of a shi 3À ligand and the methyl carbon atom of a coordinating DMF molecule of a neighboring MC (Figs. 3 and 4). These weak C-HÁ Á ÁO interactions, in addition to pure van der Waals forces, contribute to the overall packing of the molecules.

Synthesis and crystallization
The title compound was synthesized by first dissolving manganese(II) acetate tetrahydrate (2 mmol) in 4 ml of methanol and 4 ml of DMF, which resulted in a dark-orange solution. Then a mixture of salicylhydroxamic acid (2 mmol) and sodium chloroacetate (2 mmol) in 5 ml of methanol and 5 ml of DMF was added to the manganese(II) acetate solution.
The resulting dark-brown solution was stirred overnight and filtered the next day without the recovery of a precipitate. After slow evaporation of the dark-brown filtrate for 7 days, black, block-like crystals suitable for X-ray diffraction were recovered.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. The metallacrown molecule, coordinating DMF molecules, and chloroacetate anion show whole-molecule disorder over two sets of sites. The geometries of the two metallacrowns, coordinating DMF molecules, and the coordinating chloroacetate anions were restrained to be similar to each other (SAME command in SHELXL, s.u. = 0.02 Å ). For the benzene ring carbon atoms (C2-C7, C9-C14 and C2B-C7B, C9B-C14B), oxime oxygen atom (O4 and O4B), and oxime nitrogen atoms (N1, N2 and N1B, N2B) of the salicylhydroximate ligands, equivalent atoms were constrained to have pairwise identical anisotropic displacement parameters (ADPs). The ADPs of the sodium ions (Na1 and Na1B) were also constrained to be identical. For the coordinating DMF molecules, the nitrogen atoms (N3 and N3B, N4 and N4B, and N5 and N5B) have nearly the same atom positions, leading to highly correlated thermal parameters. To avoid correlation of the thermal parameters, the ADPs of equivalent nitrogen atoms in the DMF molecules were constrained to be identical. In addition, carbon, oxygen, and chlorine atoms of the chloroacetate and carbon, oxygen, and nitrogen atoms of the coordinating DMF molecules were restrained to have similar U ij components of the ADPs (s.u. = 0.04 Å 2 ; SIMU restraint in SHELXL). Anisotropic displace-   ment parameters of all atoms in the minor moiety of the coordinating DMF molecule associated with N5B were restrained using an enhanced rigid-bond restraint for the 1,2and 1,3 distances [RIGU command in SHELXL, s.u. = 0.004 Å 2 for both 1,2-and 1,3 distances (Thorn et al., 2012)]. Additionally, the following sodium-oxygen bond lengths were restrained to be similar (s.u. 0.02 Å ): Na1-O1 and Na1B-O1B, Na1-O4 and Na1B-O4B, Na1-O8 and Na1B-O8B, and Na1-O11 and Na1B-O11B. Subject to these conditions, the occupancy ratio of the disordered metallacrown and associated anion and solvent molecules refined to 0.8783 (7):0.1217 (7). A lattice DMF molecule, associated with N6, is disordered over two sets of sites with different orientations. The geometries of the two DMF molecules were restrained to be similar to each other (SAME command in SHELXL, s.u. = 0.02 Å ). The nitrogen atoms (N6 and N6B) have nearly the same atom positions, leading to highly correlated displacement parameters. To avoid correlation of the displacement parameters, the ADPs of equivalent atoms were constrained to be identical. In addition, carbon, oxygen, and nitrogen atoms of the DMF molecule were restrained to have similar U ij components of the ADPs (s.u. = 0.04 Å 2 ; SIMU restraint in SHELXL). Subject to these restraints, the occupancy ratio of the disordered DMF molecule refined to 0.615 (5):0.385 (5).
All hydrogen atoms were placed in calculated positions and refined as riding on their carrier atoms with C-H distances of 0.95 Å for sp 2 carbon atoms and 0.98 Å for methyl carbon atoms. The U iso values for hydrogen atoms were set to a multiple of the value of the carrying carbon atom (1.2 times for sp 2 -hybridized carbon atoms or 1.5 times for methyl carbon atoms and water oxygen atoms). Major disorder component methyl H atoms were allowed to rotate, but not to tip (AFIX 137 command in SHELXL). For the minor disorder component, methyl H atoms, the C-N-C-H torsion angles were constrained, as implemented in the AFIX 33 command in SHELXL.

Di-µ-chloroacetato-hexakis(dimethylformamide)tetrakis(µ-N,2-dioxidobenzene-1carboximidato)tetramanganese(III)disodium dimethylformamide disolvate
where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.85 e Å −3 Δρ min = −0.45 e Å −3 Special details Experimental. The metallacrown molecule, coordinating DMF molecules, and chloroacetate anion show whole molecule disorder over two sites. The geometries of the two metallacrowns, coordinating DMF molecules, and the coordinating chloroacetate anions were restrained to be similar to each other (SAME command in SHELXL, e.s.d. = 0.02 Angstrom). For the benzene ring carbon atoms (C2-C7, C9-C14 and C2B-C7B, C9B-C14B), oxime oxygen atom (O4 and O4b), and oxime nitrogen atoms (N1, N2 and N1B, N2B) of the salicylhydroximate ligands, equivalent atoms were constrained to have pairwise identical anisotropic displacement parameters (ADPs). The ADPs of the sodium ions (Na1 and Na1B) were also constrained to be identical. For the coordinating DMF molecules, the nitrogen atoms (N3 and N3B, N4 and N4B, and N5 and N5B) have nearly the same atom positions leading to highly correlated thermal parameters. To avoid correlation of the thermal parameters, the ADPs of equivalent nitrogen atoms in the DMF molecules were constrained to be identical. In addition, carbon, oxygen, and chlorine atoms of the chloroacetate and carbon, oxygen, and nitrogen atoms of the coordinating DMF molecules were restrained to have similar U ij components of the ADPs (e.s.d. = 0.04 Angstrom squared; SIMU restraint in Shexl). Anisotropic displacement parameters of all atoms in the minor moiety of the coordinating DMF molecule associated with N5B were restrained using an enhanced rigid bond restraint for the 1,2-and 1,3 distances [RIGU command in SHELXL, e.s.d. = 0.004 Angstrom squared for both 1,2-and 1,3 distances [Thorn, Dittrich & Sheldrick, Acta Cryst. A68 (2012) 448-451]. Additionally, the following sodium-oxygen bond distances were restrained to be similar (e.s.d. 0.02 Angstrom): Na1-O1 and Na1B-O1B, Na1-O4 and Na1B-O4B, Na1-O8 and Na1B-O8B, and Na1-O11 and Na1B-O11B. Subject to these conditions, the occupancy ratio of the disordered metallacrown and associated anion and solvent molecules refined to 0.8783 (7) to 0.1217 (7). A lattice DMF molecule, associated with N6, is disordered over two sites with different orientations. The geometries of the two DMF molecules were restrained to be similar to each other (SAME command in SHELXL, e.s.d. = 0.02 Angstrom). The nitrogen atoms (N6 and N6B) have nearly the same atom positions leading to highly correlated thermal parameters. To avoid correlation of the thermal parameters, the ADPs of equivalent atoms were constrained to be identical. In addition, carbon, oxygen, and nitrogen atoms of the DMF molecule were restrained to have similar U ij components of the ADPs (e.s.d. = 0.04 Angstrom squared; SIMU restraint in Shexltl). Subject to these restraints, the occupancy ratio of the disordered DMF molecule refined to 0.615 (5) to 0.385 (5). All hydrogen atoms were placed in calculated positions and refined as riding on their carrier atoms with C-H distances of 0.95 Angstrom for sp 2 carbon atoms and 0.98 Angstrom for methyl carbon atoms. The U iso values for hydrogen atoms were set to a multiple of the value of the carrying carbon atom (1.2 times for sp 2 -hybridized carbon atoms or 1.5 times for methyl carbon atoms and water oxygen atoms). Major moiety methyl H atoms were allowed to rotate, but not to tip (AFIX 137 command in SHELXL). For the minor moiety methyl H atoms the C-N-C-H dihedral angle were constrained as implemented in the AFIX 33 command in SHELXL. Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.