(Dimethylphosphoryl)methanaminium nitrate

In the crystal of the title salt, C3H11NOP+·NO3 −, dicationic inversion dimers are head-to-tail connected by a pair of strong N—H⋯O hydrogen bonds. The resulting graph-set descriptor of this ring system is R 2 2(10). The nitrate counter-anions connect the dicationic dimers via N—H⋯O hydrogen bonds, forming two-dimensional networks in the bc plane.

In the crystal of the title salt, C 3 H 11 NOP + ÁNO 3 À , dicationic inversion dimers are head-to-tail connected by a pair of strong N-HÁ Á ÁO hydrogen bonds. The resulting graph-set descriptor of this ring system is R 2 2 (10). The nitrate counter-anions connect the dicationic dimers via N-HÁ Á ÁO hydrogen bonds, forming two-dimensional networks in the bc plane.

Comment
There are several reports which prove the ability of the bidentate dpma ligand (dpma = (dimethylphosphoryl)methanamine) to coordinate a variety of transition metals (Dodoff et al., 1990;Borisov et al., 1994;Trendafilova et al., 1997;Kochel, 2009). Additionally, two metal complexes containing the dpmaH + cation have been structurally characterized so far (Reiss, 2013a,b). For simple dpmaH + salt structures it has been shown that this tecton (Brunet et al., 1997) can be used to construct hydrogen bonded one-dimensional polymers (Reiss & Jörgens, 2012;Lambertz et al., 2013;Buhl et al., 2013;Reiss, 2013c). Only for the double salt (H 3 O)dpmaHBr the ions are connected by hydrogen bonds, forming a two-dimensional network (Reiss, 2013d) The title compound dpmaHNO 3 crystallizes in the monoclinic space group, P2 1 /c, with one dpmaH + cation and one nitrate anion in the asymmetric unit. The angles and bond lengths of both ions are all in the typical ranges. The dpmaH + cation features the hydrogen bond donor group NH 3 + at the one end and the hydrogen bond accepting group -P=O at the other end. Therefore, this tecton in principle is capable to form connections among other dpmaH + cations and to counter anions. In the title structure two dpmaH + cations are connected by two strong, charge supported -NH + ···O=P-hydrogen bonds (N···O = 2.7493 (10) Å) head to tail forming cyclic dimers ( Fig. 1; first level graph-set descriptor: R 2 2 (10); Etter et al.,1990;Grell et al., 2002). Moreover, each dimer is associated by charge supported, strong -NH + ···OÛ N-hydrogen bonds (N···O = 2.8555 (11) Å, 2.8784 (12) Å) to four adjacent nitrate counter anions (Fig. 2). Consequently, each nitrate anion forms two hydrogen bonds to two adjacent dicationic dimers constructing a two-dimensional network in the bc plane. The dimers act as a tetradentate hydrogen bond donor. The nitrate anions act as bidentate hydrogen bond acceptors by two of their oxygen atoms.

Experimental
The title compound was synthesized by dissolving 1.07 g (10.0 mmol) (dimethylphosphoryl)methanamine in dilute nitric acid (2 ml, 12%) while the mixture was heated. After a few days colourless platelets were obtained by slow evaporation of the solvent at room temperature.

Refinement
All H-atoms were identified in difference syntheses. Hydrogen atoms at both methyl groups and at the CH 2 group were idealized and refined using a riding model (AFIX 137 (methyl)  were refined freely with individual U iso values.

Figure 1
A view of the asymmetric unit of the title structure together with a symmetry related cation and their hydrogen bonds (dashed lines) to adjacent ions. Displacement ellipsoids are drawn at the 45% probability level (′ = -x, 1 -y, -z). The green numbers mark the ring size of the first level R 2 2 (10) graph-set descriptor for the cyclic dimer consisting of two