2-Amino­anilinium phosphite

The solid-state structure of the title compound, alternatively called 2-amino­anilinium hydrogen phosphonate, C₆H₉N₂⁺·H₂PO₃^-, shows the monoprotonated di­amine mol­ecule to be multiply hydrogen bonded to HPO₃H^- anions. There is no inter-phosphite hydrogen bonding, contrary to previous solid-state observations of the species.

S1. Comment

Dihydrogen phosphite (HPO₃H₂) has been observed in the solid state both in its monoanionic and dianionic forms. There have been observations of the doubly deprotonated form (HPO₃^-2) with metallic cations: Mg(HPO₃)·6H₂O (Corbridge, 1956), Na₂(HPO₃)·5H₂O (Colton & Henn, 1971), Cu(HPO₃)·2H₂O (Handlovic, 1969); Al₂(HPO₃)₃·Ga₂(HPO₃)₃ (Morris et al., 1994), Ga₂(HPO₃)₃·4H₂O (Morris et al., 1992) are also known. The single known structure of an organic cation and (HPO₃) is (NH₄)₂(HPO₃)·5H₂O (Rafiq et al., 1982). The monoanionic form has been observed in the solid state with metallic cations in Ca(HPO₃H)₂·H₂O (Larbot et al., 1984), Cd(HPO₃H)₂·H₂O (Loub et al., 1978), Nd(HPO₃H)₂·2H₂O (Loukili et al., 1988), Fe(HPO₃H)₃ (Sghyar et al., 1991) and Zn(HPO₃H)₂.0.333H₂O (Durand et al., 1992), and also with organic cations in isopropyl ammonium phosphite (Averbuch-Pouchot, 1993a), anilinium phosphite (Adrissi et al., 2000), as well as in glycinium phosphite and glycylglycinium phosphite (Averbuch-Pouchot, 1993b). The two organic examples of HPO₃H^- show the two different types of hydrogen possible in the solid state. In isopropyl ammonium phosphite (Averbuch-Pouchot, 1993a), glycinium phosphite and glycylglycinium phosphite (Averbuch-Pouchot, 1993b), the monoanions are linked in a polymeric chain by hydrogen bonding. In anilinium phosphite (Adrissi et al., 2000), phosphite groups are hydrogen bonded in pairs which resemble the doubly hydrogen-bonded pairs normally observed in carboxylic acid species. In both arrangements, ammonium groups serve as hydrogen-bond donors in additional hydrogen bonding. We have examined the solid-state structure of the monoanionic form of dihydrogen phosphite, with o-phenylenediamine, (I), and find that contrary to previous observations, there is no hydrogen bonding between phosphite anions. The H atom on the phosphite O1 atom is donated to the amino group, H11···N2. The ammonium group of the 2-aminoanilinium species serves as a donor to the remaining phosphite O atoms, viz. H1a···O3, H1b···O3 and H1c···O2. The two H atoms of the amino group are similarly involved in hydrogen bonding to these O atoms: N2—H2a···O2 and N2—H2b···O3 (Fig. 1). Packing shows an alternation of cationic and anionic species on planes perpendicular to the c direction. Other structural details are normal. However, the average C—C distance in the phenyl ring is 1.36 Å and the C5—C6 distance is 1.346 (5) Å. The reason for these deviations from the expected values of 1.395 Å are unclear. Bond lengths reveal the protonated O1 atom to have a longer P—O bond [1.534 (2) Å] than P1—O2 [1.461 (3) Å] and P1—O3 [1.471 (2) Å], which are of similar length as a result of delocalization of the negative charge between them. The C—NH₃⁺ bond [1.422 (4) Å] is longer than the C—NH₂ bond [1.384 (4) Å], as predicted by charge considerations.

S2. Experimental

A single-crystal of the title salt was prepared by slow evaporation of a 1:1 aqueous solution of phosphorous acid (H₃PO₃) and 1,2-diaminobenzene.

S3. Refinement

H atoms on N, P and O atoms were located from a difference Fourier synthesis and then repositioned using HIMP (SHELXL97; Sheldrick, 1997) at idealized distances, i.e. N—H 0.90, P—H 1.14 and O—H 0.85 Å. H atoms of the aromatic ring were given idealized geometry, with C—H distances of 0.93 Å. The U_iso values were fixed at 0.05 Ų for all H atoms.

Computing details

Data collection: XSCANS (Siemens, 1991); cell refinement: XSCANS; data reduction: XSCANS; program(s) used to solve structure: SHELXS86 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia, 1997).

Figures

	Fig. 1. The hydrogen-bonding in C6H9N2^+·H2PO3^-. Displacement ellipsoids are shown at the 50% probability level.
	Fig. 2. Projection on the plane of the C6H9N2^+·H2PO3^- packing.

2-Aminoanilinium phosphite

Crystal data

C6H9N2^+·H2PO3^−	F(000) = 400
Mr = 190.14	Dx = 1.517 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 11.212 (8) Å	Cell parameters from 25 reflections
b = 5.992 (5) Å	θ = 4.1–9.3°
c = 13.204 (14) Å	µ = 0.30 mm^−1
β = 110.16 (3)°	T = 293 K
V = 832.7 (13) Å^3	Needle, colorless
Z = 4	0.1 × 0.1 × 0.1 mm

Data collection

Siemens P4 four-circle diffractometer	Rint = 0.066
Radiation source: fine-focus sealed tube	θmax = 26.4°, θmin = 1.9°
Highly oriented graphite crystal monochromator	h = −14→1
θ–2θ scans	k = −7→1
2306 measured reflections	l = −15→16
1672 independent reflections	3 standard reflections every 97 reflections
1359 reflections with I > 2σ(I)	intensity decay: none

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)] = 0.059	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.167	H-atom parameters constrained
S = 0.91	w = 1/[σ^2(Fo^2) + (0.1328P)^2 + 0.2326P] where P = (Fo^2 + 2Fc^2)/3
1672 reflections	(Δ/σ)max < 0.001
111 parameters	Δρmax = 0.10 e Å^−3
0 restraints	Δρmin = −0.09 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
P1	0.67177 (7)	0.06825 (11)	0.94968 (5)	0.0286 (3)
H1	0.7698	0.0370	0.9441	0.050*
O1	0.6125 (2)	−0.1656 (3)	0.93233 (15)	0.0412 (6)
H11	0.6178	−0.2240	0.9924	0.050*
O2	0.6888 (2)	0.1537 (3)	1.05738 (16)	0.0414 (6)
O3	0.5969 (2)	0.2060 (4)	0.85740 (16)	0.0396 (6)
N1	0.6391 (2)	0.5146 (4)	0.72571 (18)	0.0308 (5)
H1A	0.6478	0.4141	0.7784	0.050*
H1B	0.5636	0.5767	0.7189	0.050*
H1C	0.6404	0.4548	0.6636	0.050*
N2	0.6415 (2)	0.9039 (4)	0.61449 (19)	0.0329 (6)
H2A	0.6494	1.0469	0.5968	0.050*
H2B	0.5647	0.8894	0.6212	0.050*
C1	0.7447 (3)	0.6618 (5)	0.7634 (2)	0.0293 (6)
C2	0.7437 (3)	0.8527 (5)	0.7061 (2)	0.0316 (6)
C3	0.8496 (3)	0.9842 (5)	0.7394 (3)	0.0411 (7)
H3	0.8514	1.1153	0.7022	0.050*
C4	0.9519 (3)	0.9269 (6)	0.8255 (3)	0.0479 (8)
H4	1.0238	1.0169	0.8458	0.050*
C5	0.9505 (3)	0.7397 (6)	0.8823 (3)	0.0496 (9)
H5	1.0202	0.7030	0.9426	0.050*
C6	0.8473 (3)	0.6070 (5)	0.8507 (2)	0.0400 (7)
H6	0.8463	0.4770	0.8889	0.050*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
P1	0.0320 (4)	0.0198 (4)	0.0303 (4)	0.0012 (3)	0.0061 (3)	0.0014 (3)
O1	0.0592 (14)	0.0223 (11)	0.0342 (10)	−0.0069 (10)	0.0060 (9)	−0.0009 (8)
O2	0.0623 (14)	0.0206 (10)	0.0370 (11)	−0.0002 (10)	0.0116 (10)	−0.0017 (8)
O3	0.0435 (12)	0.0291 (11)	0.0387 (11)	−0.0012 (9)	0.0044 (9)	0.0116 (8)
N1	0.0378 (13)	0.0207 (11)	0.0300 (11)	0.0003 (10)	0.0065 (10)	0.0041 (9)
N2	0.0412 (13)	0.0178 (11)	0.0349 (12)	−0.0007 (9)	0.0070 (10)	0.0028 (9)
C1	0.0336 (14)	0.0204 (13)	0.0327 (13)	−0.0009 (11)	0.0098 (11)	−0.0016 (10)
C2	0.0376 (15)	0.0231 (13)	0.0318 (13)	0.0024 (11)	0.0089 (12)	−0.0019 (11)
C3	0.0442 (17)	0.0287 (15)	0.0500 (17)	−0.0059 (13)	0.0156 (14)	−0.0006 (13)
C4	0.0351 (16)	0.047 (2)	0.055 (2)	−0.0106 (14)	0.0066 (14)	−0.0064 (15)
C5	0.0377 (16)	0.050 (2)	0.0494 (18)	0.0050 (15)	−0.0006 (14)	0.0041 (16)
C6	0.0411 (16)	0.0344 (16)	0.0370 (15)	0.0069 (13)	0.0039 (13)	0.0076 (13)

Geometric parameters (Å, º)

P1—O2	1.461 (3)	N2—H2B	0.90
P1—O3	1.471 (2)	C1—C6	1.359 (4)
P1—O1	1.534 (2)	C1—C2	1.370 (4)
P1—H1	1.1421	C2—C3	1.365 (4)
O1—H11	0.8500	C3—C4	1.352 (5)
N1—C1	1.422 (4)	C3—H3	0.93
N1—H1A	0.90	C4—C5	1.352 (5)
N1—H1B	0.90	C4—H4	0.93
N1—H1C	0.90	C5—C6	1.346 (5)
N2—C2	1.384 (4)	C5—H5	0.93
N2—H2A	0.90	C6—H6	0.93
O2—P1—O3	117.08 (14)	C6—C1—N1	120.4 (3)
O2—P1—O1	111.72 (12)	C2—C1—N1	118.5 (3)
O3—P1—O1	107.12 (13)	C3—C2—C1	117.6 (3)
O2—P1—H1	108.3	C3—C2—N2	121.3 (3)
O3—P1—H1	109.0	C1—C2—N2	121.0 (3)
O1—P1—H1	102.6	C4—C3—C2	121.0 (3)
P1—O1—H11	110.4	C4—C3—H3	119.5
C1—N1—H1A	106.8	C2—C3—H3	119.5
C1—N1—H1B	114.8	C3—C4—C5	120.6 (3)
H1A—N1—H1B	101.6	C3—C4—H4	119.7
C1—N1—H1C	107.0	C5—C4—H4	119.7
H1A—N1—H1C	114.0	C4—C5—C6	119.4 (3)
H1B—N1—H1C	112.6	C4—C5—H5	120.3
C2—N2—H2A	108.1	C6—C5—H5	120.3
C2—N2—H2B	115.1	C1—C6—C5	120.4 (3)
H2A—N2—H2B	107.5	C1—C6—H6	119.8
C6—C1—C2	120.9 (3)	C5—C6—H6	119.8
C6—C1—C2—C3	0.5 (4)	C2—C3—C4—C5	−1.5 (6)
N1—C1—C2—C3	−175.6 (3)	C3—C4—C5—C6	1.7 (6)
C6—C1—C2—N2	177.2 (3)	C2—C1—C6—C5	−0.2 (5)
N1—C1—C2—N2	1.1 (4)	N1—C1—C6—C5	175.8 (3)
C1—C2—C3—C4	0.4 (5)	C4—C5—C6—C1	−0.9 (5)
N2—C2—C3—C4	−176.4 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1A···O3	0.90	1.84	2.690 (3)	157
N1—H1B···O3^i	0.90	1.90	2.741 (4)	155
N1—H1C···O2^ii	0.90	1.79	2.669 (4)	164
N2—H2B···O3^i	0.90	2.22	3.061 (4)	156
N2—H2A···O2^iii	0.90	1.96	2.855 (4)	172
O1—H11···N2^iv	0.85	1.88	2.719 (4)	168

Symmetry codes: (i) −x+1, y+1/2, −z+3/2; (ii) x, −y+1/2, z−1/2; (iii) x, −y+3/2, z−1/2; (iv) x, −y+1/2, z+1/2.