trans-Dichloridotetrakis[(dimethylphosphoryl)methanaminium-κO]cobalt(II) tetrachloridocobaltate(II)

The asymmetric unit of the title structure, [CoCl2(C3H11NOP)4][CoCl4]2, consists of one half of the trans-dichloridotetrakis[(dimethylphosphoryl)methanaminium]cobalt(II) tetracation lying on an inversion center and one tetrachloridocobaltate(II) dianion on a general position. Four O-coordinated cationic (dimethylphosphoryl)methanaminium (dpmaH+) ligands occupy the equatorial coordination sites, whereas the chloride ligands occupy axial positions of the roughly octahedral coordination polyhedron of the cobalt metal center. Intramolecular hydrogen bonds between the aminium groups and the O atom of the phosphoryl groups and additional hydrogen bonds between the aminium groups and the chloride ligands are present. Furthermore, four of the six H atoms not involved in intramolecular bonding of each cobalt(II) tetracation form weak hydrogen bonds to four adjacent tetrachloridocobaltate(II) counter-anions. By these intermolecular hydrogen bonds, one-dimensional polymeric strands are formed along the b-axis direction. The hydrogen bonding is analyzed using the graph-set method and the structural similarity with dpmaHCl is discussed.

The asymmetric unit of the title structure, [CoCl 2 (C 3 H 11 -NOP) 4 ][CoCl 4 ] 2 , consists of one half of the trans-dichlorido tetrakis[(dimethylphosphoryl)methanaminium]cobalt(II) tetracation lying on an inversion center and one tetrachloridocobaltate(II) dianion on a general position. Four Ocoordinated cationic (dimethylphosphoryl)methanaminium (dpmaH + ) ligands occupy the equatorial coordination sites, whereas the chloride ligands occupy axial positions of the roughly octahedral coordination polyhedron of the cobalt metal center. Intramolecular hydrogen bonds between the aminium groups and the O atom of the phosphoryl groups and additional hydrogen bonds between the aminium groups and the chloride ligands are present. Furthermore, four of the six H atoms not involved in intramolecular bonding of each cobalt(II) tetracation form weak hydrogen bonds to four adjacent tetrachloridocobaltate(II) counter-anions. By these intermolecular hydrogen bonds, one-dimensional polymeric strands are formed along the b-axis direction. The hydrogen bonding is analyzed using the graph-set method and the structural similarity with dpmaHCl is discussed.
The asymmetric unit of the title structure consists of one half of a fourfold charged trans-dichloridotetrakis((dimethylphosphoryl)methanaminium)cobalt(II) complex located on a center of inversion and a tetrachloridocobaltate(II) dianion at a general position. In the complex cation the four O-coordinated dpmaH + ligands occupy the equatorial coordination sites, whereas the chlorido ligands occupy axial positions in this roughly octahedral complex cation. The Co-O and Co -Cl distances are in the expected ranges (Girma et al., 2005, Guzei et al., 2010. The same applies to the geometrical parameters of the two crystallographically independent dpmaH ligands which are very similar and are in accord with the dpmaH + cation in dpmaHCl (Reiss & Jörgens, 2012). Each chlorido ligand of the cationic complex accepts two intramolecular hydrogen bonds of two neighbouring aminium groups (N1 and N2). There is at least one more example of the occurrence of such an intramolecular hydrogen bond between a chlorido ligand and the aminium group of a coordinated ligand at the same metal center (Kubíčk et al., 2003). Furthermore, intramolecular hydrogen bonding occurs between two crystallographically dependent aminium groups (N1, N1′) each donating a hydrogen bond to the O-atoms (O2 and O2′) of the two other dpmaH + ligands (Table 1, Fig. 1). Significantly different Co-O bond lengths (Co-O1 = 2.0738 (9) Å and Co-O2 = 2.1673 (9) Å) may be caused by this hydrogen bonding situation. Four of the six hydrogen atoms of aminium groups of each cationic complex, which are not involved in intramolecular hydrogen bonds, form hydrogen bonds to four adjacent tetrachloridocobaltate(II) dianions (Fig. 1). The tetrachloridocobaltate(II) dianion shows a seriously distorted tetrahedral geometry with Co-Cl distances from 2.2487 (4) Å to 2.3024 (4) Å and angles between 104.23 (1)° to 119.35 (1)°. Also for this ion the longest Co-Cl distances are associated with the chlorido ligands involved in hydrogen bonds. Cationic and anionic tectons construct a one-dimensional, hydrogen-bonded polymer along the b direction. The hydrogen bonding motifs can be classified using graph-set descriptors (Etter et al., 1990, Bernstein et al., 1995 as S 2 2 (6) and S 1 1 (7) for the intramolecular rings and as C 3 4 (10) for the backbone connection along the strands (Fig.  2). A third level graph-set is found (R 6 6 (22)) for the rings formed within the strands (Fig. 2). As these graph-sets seem to be unique to this class of compounds they alone are of limited value for a comparison with related structures. A better method to work out the key features of a structure is the use of the so-called constructor-graph representation (Grell et al., 2002). In this case, the complex cation can be reduced to a tecton that is able to donate at least four hydrogen bonds and supplementary materials sup-2 Acta Cryst. (2013). E69, m248-m249 the tetrachloridocobalte to a tecton that accepts at least two hydrogen bonds. Thus, the close relation of the title structure with the structure of dpmaHCl is inevitably clear (Fig. 3).

Experimental
For the synthesis of the title compound, equimolar amounts of dpma and cobalt(II)chloride tetrahydrate were dissolved in concentrated hydrochloric acid. Slow evaporation of this solution at room temperature yielded crystals suitable for a crystallographic structure determination.

Refinement
H atoms at the methyl groups were identified in difference syntheses, idealized and refined using rigid groups allowed to rotate about the P-C bond (AFIX 137 option of the SHELXL program; U iso (H) = 1.5U eq (C)) H-Atom at the methylene group using a riding model (AFIX 23 option of the SHELXL program; U iso (H) = 1.2U eq (C)). The coordinates of hydrogen atoms at the aminium groups were refined unrestrictedly with individual U iso values.

Figure 3
Constructor-graphs of the title structure and of dpmaHCl are shown in the context of their real structures to illustrate the structural similarity.