Bis(4-aminopyridinium) tetrachloridocobaltate(II)

In the title compound, (C5H7N2)2[CoCl4], the cobalt(II) ion is coordinated by four chloride ions in a slightly distorted tetrahedral geometry. The crystal packing is stabilized by intermolecular N—H⋯Cl hydrogen bonding, forming a three-dimensional network. The crystal was a non-merohedral twin emulating tetragonal symmetry, but being in fact orthorhombic.

In the title compound, (C 5 H 7 N 2 ) 2 [CoCl 4 ], the cobalt(II) ion is coordinated by four chloride ions in a slightly distorted tetrahedral geometry. The crystal packing is stabilized by intermolecular N-HÁ Á ÁCl hydrogen bonding, forming a three-dimensional network. The crystal was a non-merohedral twin emulating tetragonal symmetry, but being in fact orthorhombic.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: BT2925).
As a part of our investigation of the reactions of the 4-aminopyridine with metals, we report here the crystal structure of the title compound (I).
The asymmetric unit of (I), consists of two molecules of 4-aminopyridinium cation and a [CoCl 4 ] 2anion. The bond lengths and bond angles of the 4-aminopyridinium are comparable with the values reported earlier for the 4-aminopyridine in the its uncomplexed form (Anderson et al., 2005;Chao & Schempp, 1977). Protonation of the atoms N4 and N11 of the 4-aminopyridine leads to the widening of C3-N4-C5 and C10-N11-C12 angles in the pyridine ring to 121.3 (7)° and 120.4 (7)°, compared to 115.25 (13)° in 4-aminopyridine (Anderson et al., 2005). The 4-aminopyridine ring is essentially planar with the maximum deviation from planarity of 0.014 (3) Å for the atoms C8 and N11 respectively.
The crystal packing (Fig. 2) is consolidated by intermolecular N-H···Cl hydrogen bonding to form a three dimensional network.
Experimental 4-aminopyridine (0.094 g, 1 mmol) and and CoCl 2 (0.169 g, 1 mmol) in ethanol (10 ml each) and the solution was stirred well for 3 h. Blue crystals of (I) were obtained by slow evaporation of the solution over a period of one month.

Refinement
The crystals of (I) crystallized with nearly tetragonal lattice parameters. It was was not possible to solve and refine the structure in any tetragonal space group but it could be easily solved and refined in orthorhombic space group P2 1 2 1 2 1 .
PLATON and the intensity statistic indicate twinning. Applying the twin instruction TWIN 0 1 0 1 0 0 0 0 -1 with a BASF of 0.340 (1) the R1 value drops to 0.021 (0.095 without TWIN instruction). The nonstandard setting for the orthorhombic cell was kept to simplify the twin matrix.
All the hydrogen atoms were fixed on the calculated positions and allowed to ride on their parent atoms with the C-H = 0.95 Å (aromatic); N-H = 0.84-0.89 Å with U iso (C) in the range of 1.2U eq (C)-1.5U eq (N).