Guanidinium di­hydrogen phosphite

The structure of the title compound, CH₆N₃⁺.H₂PO₃⁻, originally determined by Krumbe & Haussuhl [Z. Kristallogr. (1987), 178, 132–134], has been redetermined. The intermolecular packing is controlled by N—H...O and O—H...O hydrogen bonds, resulting in a non-centrosymmetric three-dimensional structure.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](P-O) = 0.001 Å
• R factor = 0.029
• wR factor = 0.076
• Data-to-parameter ratio = 25.2

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


 Alert Level C:



PLAT_420  Alert C D-H Without Acceptor       P(1)   -   H(1)              ?

General Notes



REFLT_03
         From the CIF: _diffrn_reflns_theta_max           32.48
         From the CIF: _reflns_number_total               1836
         Count of symmetry unique reflns         1173
         Completeness (_total/calc)            156.52%
         TEST3: Check Friedels for noncentro structure
         Estimate of Friedel pairs measured       663
         Fraction of Friedel pairs measured     0.565
         Are heavy atom types Z>Si present          yes
          Please check that the estimate of the number of Friedel pairs is
          correct. If it is not, please give the correct count in the
          _publ_section_exptl_refinement section of the submitted CIF.


 0 Alert Level A = Potentially serious problem

 0 Alert Level B = Potential problem

 1 Alert Level C = Please check

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S1. Comment

Amine phosphates have recently been proposed as key intermediates in the synthesis of organically templated open frameworks (Rao et al., 2000). In addition, they show interesting crystal-packing motifs controlled by the interplay of N—H···O and O—H···O hydrogen bonds (Demir et al., 2002). Less is known about the crystal structures of amine–hydrogen phosphite complexes which involve the [HPO₃]²⁻ ion or its protonated derivative, [H₂PO₃]⁻. Here, we report the crystal structure of guanidinium dihydrogen phosphite, CN₃H₆⁺·H₂PO₃⁻, (I) (Fig. 1). This phase was first prepared and characterized by Krumbe & Haussuhl (1987), but a redeterination was considered worthwhile as atomic parameters were not published.

The CN₃H₆⁺ moiety [d_av(C—N) = 1.339 (2) Å; θ_av(N—C—N) = 120.0 (2)°] shows its usual `propeller' shape approximating to D_{3 h} local symmetry (Harrison & Phillips, 1997) indicating that the usual bonding model for this species to result in a C—N bond order of 1.33 is appropriate here. The dihydrogen phosphite anion possesses typical (Doran et al., 2001) geometrical parameters [d_av(P—O) = 1.547 (2) Å; θ_av(O—P—O) = 111.4 (2)°], with the P—O1H vertex significantly lengthened compared with the other P—O bonds.

The unit-cell packing (Fig. 2) involves chains of [H₂PO₃]⁻ groups propagating in the polar [010] direction, linked together via O1—H2···O3 hydrogen bonds. All six of the guanidinium H atoms are involved in N—H···O interactions (Figs. 1 and 2); O1 accepts one, O2 three, and O3 two N—H···O bonds. The resulting O(PH₃) coordinations for O2 and O3 are approximately tetrahedral. As expected (Doran et al., 2001), the P—H vertex is not involved in the hydrogen-bonding scheme.

S2. Experimental

(CN₃H₆)₂(CO₃) (0.91 g, 0.005 mmol) and H₃PO₃ (0.82 g, 0.01 mmol) were dissolved in 20 ml distilled water. Block-shaped crystals of (I) grew over the course of a few days as the solvent evaporated.

S3. Refinement

Atom H2 was located in a difference map and the other H atoms were placed in calculated positions [d(N—H) = 0.86 Å and d(P—H) = 1.32 Å]. The H atoms were included in the refinement in the riding-motion approximation, with U_iso(H) = 1.2U_eq of the carrier atom.

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. Fragment of (I) (50% displacement ellipsoids and arbitrary spheres for the H atoms), showing the atom-labelling scheme and hydrogen-bonding interactions (dashed lines). Symmetry-generated hydrogen phosphite moieties are indicated by unshaded ellipsoids; symmetry codes are as in Table 2. Note how each roughly parallel pair of guanidinium N–H bonds (H3 + H5; H6 + H8; H4 + H7) hydrogen bonds to a different acceptor configuration.

Fig. 2. The crystal packing in (I) viewed approximately down [100], with the dihydrogen phosphite tetrahedra coloured yellow. The coloured spheres, of arbitrary radii, represent O atoms (red), C atoms (blue), N atoms (green), and H atoms (grey). Hydrogen bonds are highlighted in pink.

Guanidinium dihydrogen phosphite

Crystal data

CN3H6^+·H2PO3^−	F(000) = 148
Mr = 141.07	Dx = 1.534 Mg m^−3
Monoclinic, P21	Mo Kα radiation, λ = 0.71073 Å
a = 4.5268 (3) Å	Cell parameters from 2092 reflections
b = 7.4711 (5) Å	θ = 2.3–32.3°
c = 9.1856 (6) Å	µ = 0.38 mm^−1
β = 100.631 (2)°	T = 293 K
V = 305.33 (3) Å^3	Block, colourless
Z = 2	0.32 × 0.21 × 0.16 mm

Data collection

Bruker SMART1000 CCD diffractometer	1836 independent reflections
Radiation source: fine-focus sealed tube	1691 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.015
ω scans	θmax = 32.5°, θmin = 2.3°
Absorption correction: multi-scan (SADABS; Bruker, 1999)	h = −4→6
Tmin = 0.891, Tmax = 0.944	k = −11→10
3144 measured reflections	l = −13→13

Refinement

Refinement on F^2	Hydrogen site location: geom and difmap (O-H species)
Least-squares matrix: full	H-atom parameters constrained
R[F^2 > 2σ(F^2)] = 0.029	w = 1/[σ^2(Fo^2) + (0.0506P)^2] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.076	(Δ/σ)max < 0.001
S = 0.99	Δρmax = 0.28 e Å^−3
1836 reflections	Δρmin = −0.23 e Å^−3
73 parameters	Absolute structure: Flack (1983), 1055 Friedel pairs
1 restraint	Absolute structure parameter: −0.03 (9)
Primary atom site location: structure-invariant direct methods

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
P1	0.05592 (7)	0.82326 (5)	0.67043 (3)	0.03008 (9)
H1	−0.2401	0.8142	0.6492	0.036*
O1	0.1445 (3)	1.02556 (15)	0.65761 (13)	0.0447 (3)
H2	0.0576	1.0775	0.5827	0.054*
O2	0.1744 (3)	0.76649 (18)	0.82545 (12)	0.0456 (3)
O3	0.1579 (3)	0.71352 (15)	0.55118 (12)	0.0401 (3)
C1	0.3189 (4)	0.8857 (2)	0.17856 (16)	0.0346 (3)
N1	0.4001 (4)	0.9221 (2)	0.32228 (14)	0.0434 (3)
H3	0.3291	0.8596	0.3865	0.052*
H4	0.5236	1.0081	0.3509	0.052*
N2	0.4276 (4)	0.9817 (2)	0.07947 (15)	0.0450 (3)
H5	0.3748	0.9581	−0.0133	0.054*
H6	0.5511	1.0677	0.1078	0.054*
N3	0.1295 (4)	0.7541 (2)	0.13305 (16)	0.0471 (4)
H7	0.0782	0.7317	0.0400	0.057*
H8	0.0574	0.6909	0.1965	0.057*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
P1	0.03987 (16)	0.02707 (14)	0.02260 (13)	0.00271 (16)	0.00391 (10)	0.00014 (13)
O1	0.0700 (8)	0.0256 (5)	0.0353 (5)	0.0021 (5)	0.0011 (5)	0.0008 (4)
O2	0.0709 (8)	0.0398 (6)	0.0251 (5)	0.0093 (5)	0.0062 (5)	0.0062 (4)
O3	0.0588 (7)	0.0342 (6)	0.0281 (5)	−0.0011 (5)	0.0099 (5)	−0.0076 (4)
C1	0.0439 (8)	0.0307 (6)	0.0296 (6)	0.0007 (5)	0.0079 (5)	0.0006 (5)
N1	0.0633 (9)	0.0382 (7)	0.0282 (6)	−0.0087 (6)	0.0070 (6)	−0.0010 (5)
N2	0.0636 (9)	0.0415 (7)	0.0317 (6)	−0.0156 (7)	0.0134 (6)	−0.0019 (6)
N3	0.0647 (10)	0.0446 (8)	0.0321 (6)	−0.0179 (7)	0.0093 (7)	0.0000 (5)

Geometric parameters (Å, º)

P1—O2	1.4878 (11)	C1—N1	1.3314 (19)
P1—O3	1.5073 (11)	N1—H3	0.8600
P1—O1	1.5736 (13)	N1—H4	0.8600
P1—H1	1.3200	N2—H5	0.8600
O1—H2	0.8241	N2—H6	0.8600
C1—N3	1.321 (2)	N3—H7	0.8600
C1—N2	1.3227 (19)	N3—H8	0.8600
O2—P1—O3	115.84 (7)	C1—N1—H3	120.0
O2—P1—O1	107.07 (7)	C1—N1—H4	120.0
O3—P1—O1	110.59 (7)	H3—N1—H4	120.0
O2—P1—H1	107.7	C1—N2—H5	120.0
O3—P1—H1	107.7	C1—N2—H6	120.0
O1—P1—H1	107.7	H5—N2—H6	120.0
P1—O1—H2	115.2	C1—N3—H7	120.0
N3—C1—N2	119.20 (14)	C1—N3—H8	120.0
N3—C1—N1	120.67 (15)	H7—N3—H8	120.0
N2—C1—N1	120.13 (15)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H2···O3^i	0.82	1.75	2.5602 (17)	169
N1—H4···O3^ii	0.86	2.18	3.039 (2)	174
N1—H3···O3	0.86	2.12	2.9837 (19)	178
N2—H6···O2^ii	0.86	1.96	2.820 (2)	179
N2—H5···O2^iii	0.86	2.14	2.8907 (19)	146
N3—H8···O1^iv	0.86	2.15	3.005 (2)	176
N3—H7···O2^iii	0.86	2.11	2.8714 (19)	147

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