1-Carbamoyl­guanidinium hydrogenselenite

The title compound, C₂H₇N₄O⁺·HSeO₃⁻, contains a network of 1-carbamoyl­guanidinium cations and hydrogenselenite anions. 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, resulting in a layered structure.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](Se-O) = 0.002 Å
• R factor = 0.031
• wR factor = 0.078
• Data-to-parameter ratio = 25.9

checkCIF/PLATON results

No syntax errors found



Alert level A
PLAT029_ALERT_3_A _diffrn_measured_fraction_theta_full Low .....       0.96

Alert level C
PLAT042_ALERT_1_C Calc. and Rep. MoietyFormula Strings Differ ..          ?
PLAT125_ALERT_4_C No _symmetry_space_group_name_Hall Given .....          ?

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

   1 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
   1 ALERT type 4 Improvement, methodology, query or suggestion

---

S1. Comment

The title compound, (C₂H₇N₄O)(HSeO₃), (I) (Fig. 1), contains a hydrogen-bonded network of (C₂H₇N₄O)⁺ (1-carbamoylguanidinium or guanylurea) cations and hydrogenselenite anions. It complements simple salt-like guanylurea compounds, including (C₂H₇N₄O)(ClO₄) (Begley et al., 1985), (C₂H₇N₄O)(H₂PO₄) (Zaman & Darlow, 1986), (C₂H₇N₄O)Cl·0.5H₂O (Scoponi et al., 1991) and (C₂H₇N₄O)(CH₄PO₃)·H₂O (Brauer & Kottsieper, 2003)

In (I), the (C₂H₇N₄O)⁺ cation has normal geometrical parameters (Begley et al., 1985), with d_av(N—C) = 1.343 (3) Å, indicating significant delocalization of electrons over the non-H-atom skeleton (Scopoini et al., 1991) and is almost planar (for the non-H atoms, the root-mean-square deviation from the best least-squares plane = 0.031 Å). A non-linear (θ = 128.8°) intramolecular N3—H5···O4 hydrogen bond is present, which is typical for (C₂H₇N₄O)⁺ (Bremner & Harrison, 2002). The (HSeO₃)⁻ hydrogenselenite group shows its standard (Verma, 1999) pyramidal geometry [d_av(Se—O) = 1.699 (2) Å and θ_av(O—Se—O) = 102.2 (1)°], with the protonated Se–O3 vertex showing its expected lengthening relative to the other Se—O bonds.

The component species in (I) interact by means of a network of N—H···O and O—H···O hydrogen bonds (see Table 2 for symmetry codes). The guanylurea cations form hydrogen-bonded chains (via N4—H7···O4^v bonds) crosslinked by the hydrogenselenite groups to form hydrogen-bonded layers (Fig. 2) in the (011) plane. There are various intermolecular hydrogen-bonding motifs including N—H···O_S, and bifurcated N—H···(O_S,O_S) and N—H···(O_S,O_G) (S = selenite, G = guanylurea) bonds. Based on the H···O separations, these N—H···O bonds vary in strength from fairly strong (1.98 Å) to very weak (2.53 Å). Atoms O1 and O2 accept three hydrogen bonds each, and atoms O3 and O4 accept two each.

The strong, short, inter-selenite O3—H8···O2ⁱ hydrogen bonds help to fuse the layers into double sheets (Fig. 3); when considered in isolation, pairs of (HSeO₃)⁻ units form unusual, inversion-symmetry generated, dimers by way of two such bonds (Fig. 3). Pseudo-π–π-stacking interactions between adjacent guanylurea moieties [d(N2···C4ⁱ) = 3.295 (3) Å and d(N3···N1ⁱ) = 3.437 (3) Å] may also provide some coherence between the layers. The double sheets stack normal to (011), with bonding between the double sheets controlled by van der Waals forces.

S2. Experimental

5 ml of 0.1 M `H₂SeO₃' (dissolved SeO₂) and 5 ml of 0.1 M cyanoguanidine (C₂H₄N₄) were mixed, resulting in a clear solution. Rod- and block-shaped crystals of (I) grew as the water evaporated over the course of a few days. The cyanoguanidine was transformed to guanylurea by slow acid hydrolysis.

S3. Refinement

Atom H8 was found in a difference map and refined by riding in its as-found position. H atoms bonded to nitrogen were placed in calculated positions [d(N—H) = 0.86 Å] and refined by riding. The constraint U_iso(H) = 1.2U_eq(parent atom) was applied in all cases.

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 (011) hydrogen-bonded sheet in (I) with the selenite groups represented by HSeO3E pseudo-tetrahedra (dummy atom E placed 1.0 Å from Se). Colour key: [HSeO3E]^− groups pink, O atoms red, C atoms blue, N atoms green, H atoms grey, E dummy atoms light blue (all radii arbitrary). The H···O portion of the intramolecular hydrogen bond is highlighted in light blue. The H···O portions of the N—H···O hydrogen bonds with 1.90 Å < d(H···O) < 2.30 Å and 2.30 Å < d(H···O) < 2.55 Å are highlighted in yellow and orange, respectively. Symmetry labels as in Table 2.
	Fig. 3. [010] projection of (I) showing the inter-selenite connectivity by way of hydrogen bonds. Colour key as in Fig. 1 and symmetry code as in Table 2. Guanylurea H atoms have been omitted for clarity.

(I)

Crystal data

C2H7N4O^+·HSeO3^−	Z = 2
Mr = 231.08	F(000) = 228
Triclinic, P1	Dx = 2.048 Mg m^−3
a = 6.7643 (4) Å	Mo Kα radiation, λ = 0.71073 Å
b = 7.9045 (5) Å	Cell parameters from 2368 reflections
c = 8.2612 (5) Å	θ = 2.8–32.5°
α = 63.021 (1)°	µ = 4.99 mm^−1
β = 81.414 (1)°	T = 293 K
γ = 72.200 (1)°	Block, colourless
V = 374.77 (4) Å^3	0.45 × 0.35 × 0.30 mm

Data collection

Bruker SMART1000 CCD diffractometer	2591 independent reflections
Radiation source: fine-focus sealed tube	2259 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.016
ω scans	θmax = 32.5°, θmin = 2.8°
Absorption correction: multi-scan (SADABS; Bruker, 1999)	h = −10→10
Tmin = 0.143, Tmax = 0.224	k = −11→7
3843 measured reflections	l = −12→12

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)] = 0.031	Hydrogen site location: geom (O-H) and calc (N-H)
wR(F^2) = 0.078	H-atom parameters constrained
S = 1.01	w = 1/[σ^2(Fo^2) + (0.0491P)^2] where P = (Fo^2 + 2Fc^2)/3
2591 reflections	(Δ/σ)max = 0.001
100 parameters	Δρmax = 1.00 e Å^−3
0 restraints	Δρmin = −0.66 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
Se1	0.46138 (3)	0.22877 (3)	0.59621 (3)	0.02838 (8)
O1	0.5058 (3)	0.3655 (3)	0.3802 (2)	0.0374 (4)
O2	0.2742 (3)	0.1347 (2)	0.5863 (2)	0.0370 (3)
O3	0.6765 (3)	0.0192 (3)	0.6524 (3)	0.0456 (4)
H8	0.6887	−0.0448	0.5726	0.055*
O4	−0.1792 (2)	0.6594 (3)	0.0737 (2)	0.0421 (4)
N1	−0.0675 (3)	0.4162 (3)	0.3471 (3)	0.0375 (4)
H1	−0.1853	0.3888	0.3756	0.045*
H2	0.0334	0.3503	0.4224	0.045*
N2	0.1542 (3)	0.5944 (3)	0.1572 (2)	0.0311 (4)
H3	0.2431	0.5226	0.2430	0.037*
N3	0.0864 (3)	0.8605 (3)	−0.1300 (3)	0.0370 (4)
H4	0.1293	0.9478	−0.2251	0.044*
H5	−0.0406	0.8570	−0.1221	0.044*
N4	0.4101 (3)	0.7369 (3)	−0.0081 (3)	0.0414 (5)
H6	0.4543	0.8237	−0.1026	0.050*
H7	0.4931	0.6526	0.0797	0.050*
C1	0.2143 (3)	0.7331 (3)	0.0024 (3)	0.0282 (4)
C2	−0.0415 (3)	0.5601 (3)	0.1869 (3)	0.0294 (4)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Se1	0.03106 (12)	0.02730 (11)	0.02449 (11)	−0.01114 (8)	−0.00084 (7)	−0.00710 (8)
O1	0.0357 (8)	0.0368 (9)	0.0298 (8)	−0.0181 (7)	−0.0015 (6)	−0.0006 (6)
O2	0.0345 (8)	0.0369 (8)	0.0381 (8)	−0.0193 (7)	0.0035 (6)	−0.0101 (7)
O3	0.0421 (10)	0.0418 (10)	0.0448 (10)	0.0037 (8)	−0.0196 (8)	−0.0158 (8)
O4	0.0246 (7)	0.0523 (11)	0.0352 (8)	−0.0151 (7)	−0.0062 (6)	−0.0024 (8)
N1	0.0312 (9)	0.0384 (10)	0.0322 (9)	−0.0159 (8)	−0.0016 (7)	−0.0019 (8)
N2	0.0226 (8)	0.0364 (10)	0.0249 (8)	−0.0104 (7)	−0.0044 (6)	−0.0025 (7)
N3	0.0285 (9)	0.0403 (10)	0.0299 (9)	−0.0143 (8)	−0.0052 (7)	−0.0002 (8)
N4	0.0257 (9)	0.0519 (12)	0.0376 (10)	−0.0176 (9)	−0.0023 (7)	−0.0066 (9)
C1	0.0247 (9)	0.0321 (10)	0.0257 (9)	−0.0104 (8)	−0.0014 (7)	−0.0086 (8)
C2	0.0253 (9)	0.0320 (10)	0.0272 (9)	−0.0103 (8)	−0.0002 (7)	−0.0081 (8)

Geometric parameters (Å, º)

Se1—O1	1.6523 (15)	N2—C2	1.396 (3)
Se1—O2	1.6807 (16)	N2—H3	0.8600
Se1—O3	1.7626 (17)	N3—C1	1.308 (3)
O3—H8	0.9787	N3—H4	0.8600
O4—C2	1.227 (3)	N3—H5	0.8600
N1—C2	1.328 (3)	N4—C1	1.323 (3)
N1—H1	0.8600	N4—H6	0.8600
N1—H2	0.8600	N4—H7	0.8600
N2—C1	1.359 (3)
O1—Se1—O2	103.10 (8)	C1—N3—H5	120.0
O1—Se1—O3	102.92 (9)	H4—N3—H5	120.0
O2—Se1—O3	100.48 (9)	C1—N4—H6	120.0
Se1—O3—H8	111.7	C1—N4—H7	120.0
C2—N1—H1	120.0	H6—N4—H7	120.0
C2—N1—H2	120.0	N3—C1—N4	120.6 (2)
H1—N1—H2	120.0	N3—C1—N2	122.58 (19)
C1—N2—C2	124.68 (17)	N4—C1—N2	116.81 (19)
C1—N2—H3	117.7	O4—C2—N1	123.2 (2)
C2—N2—H3	117.7	O4—C2—N2	121.83 (19)
C1—N3—H4	120.0	N1—C2—N2	114.98 (18)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O3—H8···O2^i	0.98	1.71	2.685 (3)	173
N1—H1···O1^ii	0.86	2.15	2.990 (3)	167
N1—H2···O2	0.86	2.06	2.903 (3)	165
N2—H3···O1	0.86	1.99	2.824 (2)	163
N3—H4···O2^iii	0.86	1.98	2.826 (2)	169
N3—H5···O4	0.86	2.02	2.646 (3)	129
N3—H5···O3^iv	0.86	2.48	3.132 (2)	133
N4—H6···O3^iii	0.86	2.53	3.372 (3)	165
N4—H7···O4^v	0.86	2.23	2.774 (2)	122
N4—H7···O1	0.86	2.48	3.200 (3)	142

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