Propane-1,2-diammonium chromate(VI)

In the title molecular salt, (C3H12N2)[CrO4], each chromate anion accepts six N—H⋯O and C—H⋯O hydrogen bonds from nearby propane-1,2-diammonium cations. Three of the four O atoms of the chromate anion accept these bonds; the remaining Cr—O bond length is notably shorter than the others. In the crystal, the anions and cations stack in layers lying parallel to (100): the hydrogen-bonding pattern leads to a three-dimensional network.

In the title molecular salt, (C 3 H 12 N 2 )[CrO 4 ], each chromate anion accepts six N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds from nearby propane-1,2-diammonium cations. Three of the four O atoms of the chromate anion accept these bonds; the remaining Cr-O bond length is notably shorter than the others. In the crystal, the anions and cations stack in layers lying parallel to (100): the hydrogen-bonding pattern leads to a three-dimensional network.
The asymmetric unit of (I) consists of one chromate anion and one propane-1,2-ammonium dication ( Figure 1). The structure of the compound consists of discrete chromate ions stacked in layers parallel to the (100) plane, separated by organic cations (Figure 2). The structural cohesion is established by a three-dimensional network of N-H···O and C-H···O hydrogen bonds. Geometrical characteristics of the chromate anion are slightly different (Table 1). The distance Cr -O3 is notably the shortest (1.6182 (13) Å) because O3 is not applied in any hydrogen bond (Table 2) at the same time as Cr-O4 distance is the longest (1.6879 (13) Å) because O4 is applied in three hydrogen bonds. These geometrical features have also been noticed in other crystal structures (Chebbi & Driss, 2002;2004;Srinivasan,et al., 2003).
The 1,2-propanediammonium cation is characterized by N-C-C-N and N-C-C-C torsion angles of 164.88 (14) and -74.50 (19)°, respectively. Each organic entity is bounded to six different chromate anions through eight N-H···O and C-H···O hydrogen bonds forming a three dimensional network. Examination of the 1,2-propanediammonium cation shows that the bond distances and angles show no significant difference from those obtained in other simple salts involving the same organic groups (Pospieszna-Markiewicz,et al., 2011;Gerrard,et al., 2002;Lee, et al., 2003;Todd,et al., 2005).
The established weak H-bonds (Brown, 1976;Blessing, 1986) of types N-H···O and C-H···O involve oxygen atoms of the chromate anions as acceptors, and the protonated nitrogen atoms and carbon atoms of 1,2-diammoniumpropane as donors.

Experimental
CrO 3 (0.10 g, 1 mmol) and 1,2-diaminopropane (0.13 ml, 1 mmol) were dissolved in distilled water (20 ml). The resulting solution was stirred for 30 min. and then evaporated slowly at room temperature. Yellow prisms of the title compound were obtained from the solution after one week.

Refinement
The hydrogen atoms bonded to N1 and N2 were located from a difference map and were allowed to refine. The rest of the H atoms were treated as riding, with C-H = 0.99 Å (methylene) or 0.98 Å (methyl) or 1.00 Å (methine), with U iso (H) = 1.2Ueq(parent C atoms) and 1.5Ueq(parent N or C-methyl atoms).    Projection of (I) along the c axis. The H-atoms not involved in H-bonding are omitted.

Propane-1,2-diammonium chromate(VI)
Crystal data (C 3  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 > σ(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.