Crystal structure of ammonium bis[(pyridin-2-yl)methyl]ammonium dichloride

In the title molecular salt, C12H14N3 +·NH4 +·2Cl−, the central, secondary-amine, N atom is protonated. The bis[(pyridin-2-yl)methyl]ammonium and ammonium cations both lie across a twofold rotation axis. The dihedral angles between the planes of the pyridine rings is 68.43 (8)°. In the crystal, N—H⋯N and N—H⋯Cl hydrogen bonds link the components of the structure, forming a two-dimensional network parallel to (010). In addition, weak C—H⋯Cl hydrogen bonds exist within the two-dimensional network.


S2. Structural commentary
The molecular structure of the title compound is shown in Fig 1. The bis[(pyridin-2-yl)methyl]ammonium and ammonium cations both lie across a twofold rotation axis. The dihedral angles between the pyridine rings is 68.43 (8)°. This is in contrast to the values of the dihedral anlges in bis(2-pyridylmethyl)ammonium bromide and bis(2-pyridylmethyl)ammonium iodide (Junk et al., 2006) which are 38.47 (13) and 5.17 (9)°, respectively. In the crystal, N-H···N and N-H···Cl hydrogen bonds link the components of the structure forming a two-dimensional network parallel to (010) (Fig. 2). In addition, weak C-H···Cl hydrogen bonds exist within the two-dimensional network.

S3. Synthesis and crystallization
Bis(2-pyridylmethyl)amine salt (BPMA) was synthesized and purified following literature procedures (Carvalho et al., 2006) and the reaction scheme is shown in Fig. 3. A 500 mL round bottom flask was filled with 100 mL of methanol then 2-pyridinecarboxaldehyde (8.90 mL, 94.0 mmol) added. The flask was placed in an ice bath to cool with the solution mixing. After 15 minutes, 2-pyridylmethylamine (9.70 mL, 94.0 mmol) was added to give a dull yellow colored solution.
Flask was removed from ice bath and mixture allowed to react at room temperature for 1 hour to give a red colored solution. The flask was placed back in an ice bath and sodium borohydride (3.500 g, 94.0 mmol) was added in small amounts to prevent foaming. After this addition, the flask was removed from the ice bath and the mixture left to stir overnight. Concentrated hydrochloric acid was added to the mixture drop-wise until a pH of 4 was attained producing an orange mixture. An extraction was performed on the mixture in a separatory funnel with dichloromethane until the supporting information sup-2 Acta Cryst. (2015). E71, o692-o693 organic phase became colorless. The aqueous phase was separated and its pH adjusted to 10 with Na 2 CO 3 . A second extraction was performed with dichloromethane on this mixture and the organic layer isolated and dried using MgSO 4 .
Solvent was removed to produce the desired ligand as a dark-brown colored oil (14.910 g, 80% for X-Ray analysis were obtained from slow cooling of BPMA ligand in the refrigerator.

S4. Refinement
All H atoms, except for those of the ammonium cation, were placed in calculated positions and refined in a riding-model approximation, with C-H = 0.95 -0.99 Å, N-H = 0.91 Å and U iso (H) = 1.2U eq (C,N). The two unique H atoms of the ammonium cation were refined indpendently with isotropic displacement parameters.

Figure 1
The molecular structure, shown with 50% probability ellipsoids for non-H atoms and circles of arbitrary size for H atoms Part of the crystal structure with hydrogen bonds shown as dashed lines.   (6) 0.0194 (6) 0.0008 (5) 0.0020 (5) −0.0002 (5)