Propane-1,2-di­ammonium hydrogenarsenate monohydrate

The title compound, [H₃NCH₂CH(NH₃)CH₃][HAsO₄]·H₂O, contains a network of doubly protonated propane-1,2-di­ammonium cations, hydrogenarsenate anions [d_av(As—O) = 1.682 (1) Å] and water mol­ecules. Crystal symmetry generates a racemic mixture of the two enantiomers of the organic species. The crystal packing is controlled by N—H...O [d_av(H...O) = 1.89 Å, θ_av(N—H...O) = 167° and d_av(N...O) = 2.760 (1) Å] and O—H...O [d_av(H...O) = 1.86 Å, θ_av(O—H...O) = 175° and d_av(O...O) = 2.712 (1) Å] hydrogen bonds. It is isostructural with its hydrogenphosphate congener.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.023
• wR factor = 0.051
• Data-to-parameter ratio = 31.3

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT029_ALERT_3_C _diffrn_measured_fraction_theta_full Low .....       0.99
PLAT125_ALERT_4_C No _symmetry_space_group_name_Hall Given .....          ?
PLAT790_ALERT_4_C Centre of Gravity not Within Unit Cell: Resd.#          3
              H2 O

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   3 ALERT level C = Check and explain
   0 ALERT level G = General alerts; check

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   0 ALERT type 2 Indicator that the structure model may be wrong or deficient
   1 ALERT type 3 Indicator that the structure quality may be low
   2 ALERT type 4 Improvement, methodology, query or suggestion

---

S1. Comment

The title compound, (I) (Fig. 1), complements recently reported (protonated) amine phosphates, such as triethanolammonium dihydrogenphosphate, NH(CH₂CH₂OH)₃·H₂PO₄ (Demir et al., 2003). It is isostructural with its hydrogenphosphate congener, [H₃NCH₂CH(NH₃)CH₃](HPO₄)·H₂O (Baouab & Jouini, 1998). One interesting use of [H₃NCH₂CH(NH₃)CH₃]²⁺ is as a template in the synthesis of new open-framework materials (Natarajan, 1999).

The structure of (I) contains propane-1,2-diammonium cations, hydrogenarsenate (HAsO₄)²⁻ anions and water molecules. Each [H₃NCH₂CH(NH₃)CH₃]²⁺ molecule is chiral (in the asymmetric unit, atom C2 has an R configuration), with crystal symmetry generating a 50:50 mixture of the two enantiomers, which is consistent with the racemic starting material. Its geometrical parameters [d_av(C—N) = 1.495 (2) Å and d_av(C—C) = 1.516 (2) Å] are similar to those of the same cation in [H₃NCH₂CH(NH₃)CH₃](BF₄) (Gerrard & Weller, 2002). The (HAsO₄)²⁻ hydrogenarsenate group shows its standard tetrahedral geometry [d_av(As—O) = 1.682 (1) Å and θ_av(O—As—O) = 109.4 (1)°], with the protonated As–O4 vertex showing its expected lengthening relative to the other As—O bonds.

As well as electrostatic attractions, the component species in (I) interact by means of a network of N—H···O and O—H···O links (Table 2). The (HAsO₄)²⁻ units and the water molecule (atom O5) are linked into a polymeric chain in the [010] direction by hydrogen bonds mediated by the water molecules (Fig. 2); each hydrogenarsenate tetrahedron is associated with three water neighbouring molecules. There are no direct inter-tetrahedral As—OH···O—As bonds, contrary to the commonly seen P—OH···O—P bonds in amine phosphates (Demir et al., 2003).

The organic species crosslink the chains in the [100] and [010] directions by way of N—H···O—As hydrogen bonds (Table 2). All six of the –NH₃⁺ H atoms are involved in these links [d_av(H···O) = 1.89 Å, θ_av(N—H···O) = 166.9° and d_av(N···O) = 2.760 (1) Å]. This results in pseudo (001) layers of alternating hydrogenarsenate/water and organic moieties (Fig. 3).

A short C1—H8···O4ⁱⁱ intermolecular contact [d(C—H) = 0.97 Å, d(H···O) = 2.51 Å, θ(C—H···O) = 138.1° and d(C···O) = 3.2929 (19) Å] was identified in a PLATON (Spek, 2003) analysis of the structure. If it not merely a packing artefact, it may provide some additional coherence betweem the (001) pseudo-layers.

S2. Experimental

Ra cemic propane-1,2-diammonium (1 ml) was added to 8 ml of 0.5 M H₃AsO₄ giving a clear solution. Chunky faceted crystals of (I) grew as the water evaporated over the course of a few days.

S3. Refinement

O–H hydrogen atoms were found in difference maps and were refined by riding in their as-found positions. H atoms bonded to carbon and nitrogen were placed in calculated positions [d(C—H) = 0.96–0.98 Å and d(N—H) = 0.89 Å] and refined as riding [free rotation of the rigid R—NH₃ and R—CH₃ groups about the R—N and R—C bonds, respectively, was allowed by means of SHELXL97 (Sheldrick, 1997) AFIX 137 cards].

Computing details

Data collection: SMART (Bruker, 1999); cell refinement: SAINT (Bruker, 1999); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97; molecular graphics: ORTEP-3 (Farrugia, 1997) and ATOMS (Shape Software, 1999); software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. The asymmetric unit of (I) (50% displacement ellipsoids). H atoms are drawn as small spheres of arbitrary radius and hydrogen bonds are indicated by dashed lines.
	Fig. 2. Detail of a hydrogen-bonded dihydrogenarsenate/water chain in (I) Colour key: [HAsO4]^2− tetrahedra green, O atoms rose and H atoms grey. The H···O portions of the hydrogen bonds are highlighted in yellow. Symmetry codes as in Table 2; additionally (vi) x, 1 − y, z; (vii) −1/2 − x, y − 1/2, 1/2 − z.
	Fig. 3. [010] projection of (I). Colour key as in Fig. 2; additionally C atoms blue, N atoms green. The H···O portions of the hydrogen bonds are highlighted in yellow.

(I)

Crystal data

(C3H12N2)[HAsO4]·H2O	F(000) = 480
Mr = 234.09	Dx = 1.734 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
a = 10.9115 (5) Å	Cell parameters from 3887 reflections
b = 6.1530 (3) Å	θ = 2.4–32.2°
c = 13.3653 (6) Å	µ = 3.78 mm^−1
β = 92.315 (1)°	T = 293 K
V = 896.59 (7) Å^3	Chunk, colourless
Z = 4	0.23 × 0.21 × 0.19 mm

Data collection

Bruker SMART1000 CCD diffractometer	3224 independent reflections
Radiation source: fine-focus sealed tube	2519 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.022
ω scans	θmax = 32.5°, θmin = 2.4°
Absorption correction: multi-scan (SADBAS; Bruker, 1999)	h = −16→15
Tmin = 0.431, Tmax = 0.488	k = −9→5
8758 measured reflections	l = −19→20

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.023	Hydrogen site location: difmap (O-H) and geom (N-H, C-H)
wR(F^2) = 0.051	H-atom parameters constrained
S = 0.92	w = 1/[σ^2(Fo^2) + (0.0251P)^2] where P = (Fo^2 + 2Fc^2)/3
3224 reflections	(Δ/σ)max = 0.001
103 parameters	Δρmax = 0.42 e Å^−3
0 restraints	Δρmin = −0.33 e Å^−3

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
As1	0.001478 (13)	0.13876 (2)	0.203532 (10)	0.02109 (5)
O1	0.12954 (10)	−0.00642 (19)	0.21175 (8)	0.0323 (3)
O2	−0.12469 (10)	−0.01347 (19)	0.19198 (9)	0.0354 (3)
O3	0.00525 (10)	0.32636 (18)	0.11311 (8)	0.0319 (2)
O4	0.00121 (11)	0.2754 (2)	0.31667 (8)	0.0385 (3)
H1	−0.0436	0.3882	0.3140	0.046*
N1	0.20796 (12)	0.6149 (2)	0.13668 (10)	0.0288 (3)
H2	0.1813	0.7433	0.1573	0.035*
H3	0.2650	0.5649	0.1802	0.035*
H4	0.1456	0.5217	0.1323	0.035*
N2	0.14992 (12)	0.3446 (2)	−0.05134 (9)	0.0288 (3)
H5	0.1099	0.4473	−0.0863	0.035*
H6	0.1083	0.3112	0.0025	0.035*
H7	0.1574	0.2268	−0.0893	0.035*
C1	0.26149 (15)	0.6395 (3)	0.03651 (12)	0.0306 (3)
H8	0.3416	0.7069	0.0450	0.037*
H9	0.2098	0.7363	−0.0039	0.037*
C2	0.27488 (14)	0.4264 (3)	−0.01915 (11)	0.0292 (3)
H10	0.3192	0.4572	−0.0799	0.035*
C3	0.34566 (16)	0.2523 (3)	0.03851 (13)	0.0385 (4)
H11	0.3567	0.1286	−0.0040	0.046*
H12	0.3008	0.2094	0.0956	0.046*
H13	0.4243	0.3082	0.0605	0.046*
O5	−0.14005 (11)	0.6264 (2)	0.31626 (11)	0.0449 (3)
H14	−0.2198	0.5925	0.3109	0.054*
H15	−0.1393	0.7316	0.2785	0.054*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
As1	0.02180 (7)	0.01843 (7)	0.02295 (7)	0.00023 (6)	−0.00027 (5)	−0.00066 (6)
O1	0.0286 (6)	0.0297 (6)	0.0381 (6)	0.0103 (5)	−0.0038 (5)	−0.0061 (5)
O2	0.0274 (6)	0.0282 (6)	0.0505 (7)	−0.0070 (5)	0.0020 (5)	−0.0034 (6)
O3	0.0341 (6)	0.0296 (6)	0.0318 (5)	0.0010 (5)	0.0012 (4)	0.0094 (5)
O4	0.0514 (8)	0.0351 (7)	0.0284 (6)	0.0137 (6)	−0.0059 (5)	−0.0092 (5)
N1	0.0292 (6)	0.0239 (7)	0.0328 (6)	0.0012 (5)	−0.0043 (5)	−0.0056 (6)
N2	0.0350 (7)	0.0257 (7)	0.0254 (6)	0.0007 (6)	−0.0010 (5)	−0.0013 (5)
C1	0.0345 (8)	0.0249 (8)	0.0318 (8)	−0.0038 (7)	−0.0035 (6)	0.0018 (7)
C2	0.0296 (8)	0.0299 (8)	0.0284 (7)	−0.0003 (7)	0.0034 (6)	0.0004 (7)
C3	0.0370 (9)	0.0378 (10)	0.0405 (9)	0.0113 (8)	0.0003 (7)	−0.0009 (8)
O5	0.0354 (7)	0.0348 (7)	0.0651 (8)	0.0054 (6)	0.0078 (6)	0.0111 (6)

Geometric parameters (Å, º)

As1—O1	1.6583 (10)	N2—H7	0.8900
As1—O2	1.6671 (11)	C1—C2	1.517 (2)
As1—O3	1.6730 (11)	C1—H8	0.9700
As1—O4	1.7302 (11)	C1—H9	0.9700
O4—H1	0.8489	C2—C3	1.514 (2)
N1—C1	1.490 (2)	C2—H10	0.9800
N1—H2	0.8900	C3—H11	0.9600
N1—H3	0.8900	C3—H12	0.9600
N1—H4	0.8900	C3—H13	0.9600
N2—C2	1.500 (2)	O5—H14	0.8953
N2—H5	0.8900	O5—H15	0.8211
N2—H6	0.8900
O1—As1—O2	113.20 (6)	N1—C1—C2	113.69 (13)
O1—As1—O3	111.98 (6)	N1—C1—H8	108.8
O2—As1—O3	111.41 (6)	C2—C1—H8	108.8
O1—As1—O4	103.59 (5)	N1—C1—H9	108.8
O2—As1—O4	108.87 (6)	C2—C1—H9	108.8
O3—As1—O4	107.28 (6)	H8—C1—H9	107.7
As1—O4—H1	112.5	N2—C2—C3	110.33 (14)
C1—N1—H2	109.5	N2—C2—C1	109.04 (13)
C1—N1—H3	109.5	C3—C2—C1	114.80 (13)
H2—N1—H3	109.5	N2—C2—H10	107.5
C1—N1—H4	109.5	C3—C2—H10	107.5
H2—N1—H4	109.5	C1—C2—H10	107.5
H3—N1—H4	109.5	C2—C3—H11	109.5
C2—N2—H5	109.5	C2—C3—H12	109.5
C2—N2—H6	109.5	H11—C3—H12	109.5
H5—N2—H6	109.5	C2—C3—H13	109.5
C2—N2—H7	109.5	H11—C3—H13	109.5
H5—N2—H7	109.5	H12—C3—H13	109.5
H6—N2—H7	109.5	H14—O5—H15	99.7
N1—C1—C2—C3	−54.09 (18)	N1—C1—C2—N2	70.26 (16)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O4—H1···O5	0.85	1.81	2.6534 (17)	177
N1—H2···O1^i	0.89	1.80	2.6904 (17)	174
N1—H3···O1^ii	0.89	1.86	2.7412 (17)	169
N1—H4···O3	0.89	1.96	2.8436 (18)	176
N2—H5···O3^iii	0.89	1.90	2.7449 (17)	158
N2—H6···O3	0.89	1.90	2.7596 (17)	163
N2—H7···O2^iv	0.89	1.92	2.7782 (17)	161
O5—H14···O2^v	0.90	1.82	2.7056 (17)	172
O5—H15···O2^i	0.82	1.96	2.7782 (17)	176

Symmetry codes: (i) x, y+1, z; (ii) −x+1/2, y+1/2, −z+1/2; (iii) −x, −y+1, −z; (iv) −x, −y, −z; (v) −x−1/2, y+1/2, −z+1/2.