Chloridotetrapyridinecopper(II) dicyanamidate pyridine disolvate

In the crystal structure of the title compound, [CuCl(C5H5N)4][N(CN)2]·2C6H5N, the copper(II) cations are coordinated by one chloride anion and four N-bonded pyridine ligands into discrete complexes. The copper(II) cation shows a square-pyramidal coordination environment, with the chloride anion in the apical position. However, there is one additional chloride anion at 3.0065 (9) Å, leading to a disorted octahedral coordination mode for copper. The copper(II) cation, the chloride ligand and the central N atom of the dicyanamide anion are located on twofold rotation axes. Two pyridine solvent molecules are observed in general positions.

In the crystal structure of the title compound, [CuCl(C 5 H 5 N) 4 ][N(CN) 2 ]Á2C 6 H 5 N, the copper(II) cations are coordinated by one chloride anion and four N-bonded pyridine ligands into discrete complexes. The copper(II) cation shows a square-pyramidal coordination environment, with the chloride anion in the apical position. However, there is one additional chloride anion at 3.0065 (9) Å , leading to a disorted octahedral coordination mode for copper. The copper(II) cation, the chloride ligand and the central N atom of the dicyanamide anion are located on twofold rotation axes. Two pyridine solvent molecules are observed in general positions.

Related literature
For background to this work, see: Wriedt et al. (2009a,b). For structures of transition metal dicyanamides, see: Wriedt & Nä ther (2011) and for a related structure, see: Potočň á k et al. (2006). For a description of the Cambridge Structural Database, see: Allen (2002).

Comment
In our recent work we have shown that thermal decomposition reactions are an elegant route for the discovery and preparation of new ligand-deficient coordination polymers based on transition metal thiocyanates and N-donor ligands (Wriedt et al. 2009a,b). In further investigations we have shown that new transition metal dicyanamides can also be prepared by this route (Wriedt & Näther, 2011). In order to prepare new precursors with pyridine ligands we have reacted copper (II) chloride, sodium dicyanamide and pyridine. In this reaction single crystals of the title compound were obtained by accident, which were characterized by single crystal X-ray diffraction.
In the crystal structure of the title compound each copper (II) cation is coordinated by one chloride anion and by four pyridine ligands into discrete complexes which are located on a 2-fold rotation axis (Fig. 1). The copper(II) cations are in a slightly distorted square pyramidal coordination with two Cu-N distances of 2.0511 (16) Å, two Cu-N distances of 2.0374 (16) Å and one Cu-Cl distance of 2.7344 (9) Å. The angles around the copper(II) cations ranges from 87.76 (6)° to 91.59 (6) ° (Tab. 1). There is one additional chloride anion at 3.0065 (9) Å. If this distance is considered in copper coordination the coordination polyhedron can be described as a slightly disorted octahedron. The discrete complexes are stacked into columns that elongate in the direction of the c-axis (Fig. 2). Between these columns additional pyridine molecules as well as non-coordinated dicyanamide anions are located (Fig. 2). The distances between the discrete complexe cations [CuCl(pyridine)] + and the non-coordinated [N(CN 2 )]anions amounts to 7.469 (3) Å and the shortest Cu···Cu distances amount to 5.7409 (5) Å.

Experimental
Copper (II) chloride dihydrate (CuCl 2 × 2 H 2 O) and sodium dicyanamide (Na(dca)) were obtained from Alfa Aesar and pyridine was obtained from Riedel de Haen. All chemicals were used without further purification. 0.25 mmol (42.62 mg) CuCl 2 × 2 H 2 O and 0.5 mmol (44.51 mg) Na(dca) were reacted in 0.5 ml pyridine. Blue single crystals of the title compound were obtained after one day.

Refinement
H atoms were positioned with idealized geometry and were refined isotropically with U iso (H) = 1.2 U eq (C) and C-H distances of 0.95 Å using a riding model. The absolute structure was determined on the basis of 1740 Friedel pairs but the crystal investigated was racemically twinned. Therefore, a twin refinement was performed (BASF parameter: 0.25 (2).  Fig. 1. : Crystal structure of the title compound with labelling and displacement ellipsoids drawn at the 50% probability level. Symmetry codes: i = -x+1, -y+1, z; ii = -x+2, -y+1, z.

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.
Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.