Bis(tetrabutylammonium) tetrachloridomanganate(II) dichloromethane disolvate

The ionic title compound consists of a 2:1 ratio of the tetrabutylammonium cation (1+) and the tetrachloridomanganate(II) anion (2–). The structure reported contains two dichloromethane solvent molecules co-crystallized per anion.

The title compound, (C 16 H 36 N) 2 [MnCl 4 ]Á2CH 2 Cl 2 , is an ionic organic-inorganic hybride compound consisting of a tetrabutylammonium cation and a tetrachloridomanganate(II) anion in a 2:1 stoichiometric ratio. The cation contains a central nitrogen atom bonded to four n-butyl groups in a tetrahedral arrangement, while the anion contains a central Mn II atom tetrahedrally coordinated by four chlorido ligands. It co-crystallized with two equivalents of dichloromethane solvent, CH 2 Cl 2 , to give the following empirical formula: [(C 4 H 9 ) 4 N] 2 [MnCl 4 ]Á(CH 2 Cl 2 ) 2 . The crystal structure is mainly stabilized by Coulombic interactions.

Structure description
During our efforts to prepare novel manganese-containing coordination complexes, we synthesized the previously reported non-solvated compound bis(tetrabutylammonium) tetrachloridomanganate(II). In conducting our experiments, we inadvertently obtained the disolvated title compound and determined its crystal structure. After reviewing the literature, we realised that no crystallographic data had yet been reported on either the non-solvated or solvated forms of this substance. The only crystallographic data related to this system was the powder X-ray diffraction data for the non-solvated form at 900 K after it had already undergone thermal decomposition (Styczeń et al., 2009). Herein we present the results of the single-crystal structure analysis of the title compound.
The structural formula shows a ratio of 2:1 for the tetrabutylammonium cation and the tetrachloridomanganate(II) anion, combined with two solvent molecules of dichloromethane (Fig. 1). The above three molecular entities have internal symmetries allowing them to occupy different special positions in the lattice with point group symmetries 4.. (multiplicity 4, Wyckoff letter a) for the anion, and .2. (8 d) both for the cation and the solvent molecule. The root-mean-square deviations from ideal T d symmetry for the data reports anion, S 4 symmetry for the cation and C 2v symmetry for the solvent molecule amount to 0.0123, 0.0501 and 0 Å , respectively, as calculated with PLATON (Spek, 2020), based on the SYMMOL program by Pilati & Forni (1998, 2000. The tetrabutylammonium cation, (C 4 H 9 ) 4 N + , consists of a central nitrogen atom tetrahedrally surrounded by ordered butyl groups, with N-C bond lengths ranging from 1.505 (12) Å to 1.511 (11) Å and C-N-C bond angles in the range of 105.8 (5)-111.7 (11) . The complex anion MnCl 4 2is consistent with the structure previously published for the tetramethylammonium salt (Rodríguez-Lazcano et al., 2009) -the central Mn II atom is bound with four chloride ligands tetrahedrally arranged. The Cl-Mn-Cl bond angles are 108.80 (12)-109.81 (12) . The Mn-Cl bond lengths are all 2.364 (2) Å .
The crystal structure ( Fig. 2) is stabilized primarily by Coulombic forces in the absence of classical hydrogenbonding interactions.

Figure 1
Molecular structures of the entities present in the title compound, with displacement ellipsoids drawn at the 50% probability level.  obtained from a mixture of dichloromethane/ether during a reaction involving the non-solvated form of the title compound as the starting material.

Refinement
Crystal data, data collection and structure refinement details for the reported structure is summarized in Table 1. The crystal diffracted poorly at high resolution. The average intensity drops below the 3 level at 0.9933 Å . Consequently, the reliability factors are comparatively high. As a result of the special symmetry of the dichloromethane solvent molecule, the two H atoms (H9A and H9B) were refined with halfoccupancy.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.