2-Chloro­benzene-1,4-diaminium bis­(dihydrogenphosphate)

The asymmetric unit of the title salt, C₆H₉ClN₂²⁺·2H₂PO₄⁻, contains two dihydrogenphosphate anions and one 2-chloro­benzene-1,4-diaminium dication. The H₂PO₄⁻ anions are inter­connected through strong O—H...O hydrogen bonds to form two-dimensional infinite layers parallel to (001). The organic entities are anchored to the inorganic layers through N—H...O hydrogen bonds, and through weak C—Cl...O halogen bonds [3.159 (2) Å, 140.48 (7)°]. No π–π stacking inter­actions between neighboring aromatic rings or C—H...π inter­actions towards them are observed. Minor disorder is observed for the Cl atom and one hy­droxy group [minor-component occupancy = 3.29 (9)%].

Key indicators

• Single-crystal X-ray study
• T = 100 K
• Mean [sigma](C-C) = 0.002 Å
• Disorder in main residue
• R factor = 0.025
• wR factor = 0.064
• Data-to-parameter ratio = 22.2

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT790_ALERT_4_C Centre of Gravity not Within Unit Cell: Resd.  #          1
              C6 H9 Cl N2
PLAT910_ALERT_3_C Missing # of FCF Reflections Below Th(Min) .....          1
PLAT911_ALERT_3_C Missing # FCF Refl Between THmin & STh/L=  0.600         20
PLAT913_ALERT_3_C Missing # of Very Strong Reflections in FCF ....         11
PLAT915_ALERT_3_C Low Friedel Pair Coverage ......................         90 Perc.

Alert level G
PLAT005_ALERT_5_G No _iucr_refine_instructions_details  in the CIF          ?
PLAT007_ALERT_5_G Note: Number of Unrefined D-H Atoms ............         11
PLAT033_ALERT_4_G Flack x Value Deviates .gt. 2*sigma from Zero ..      0.110
PLAT301_ALERT_3_G Note: Main Residue  Disorder ...................         11 Perc.
PLAT790_ALERT_4_G Centre of Gravity not Within Unit Cell: Resd.  #          2
              H2 O4 P
PLAT790_ALERT_4_G Centre of Gravity not Within Unit Cell: Resd.  #          3
              H2 O4 P
PLAT912_ALERT_4_G Missing # of FCF Reflections Above STh/L=  0.600         96

   0 ALERT level A = Most likely a serious problem - resolve or explain
   0 ALERT level B = A potentially serious problem, consider carefully
   5 ALERT level C = Check. Ensure it is not caused by an omission or oversight
   7 ALERT level G = General information/check it is not something unexpected

   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
   5 ALERT type 3 Indicator that the structure quality may be low
   5 ALERT type 4 Improvement, methodology, query or suggestion
   2 ALERT type 5 Informative message, check

---

S1. Comment

In organic-cation monophosphates, the phosphate anions generally observed are the partially protonated acidic ones H₂PO₄^- or HPO₄^2-. In the solid state such anions are generally interconnected through strong hydrogen bonds so as to build infinite networks with various geometries (Rayes et al., 2004; Oueslati et al., 2005). If these organic-cation monophosphates hybrid materials crystallize in a noncentrosymmetric setting they are of particular interest as nonlinear optical (NLO) materials (Masse et al., 1993). The present work is devoted to the structure of an organic-cation hydrogenphosphate, C₆H₉ClN₂(H₂PO₄)₂, formed by the reaction of 2-chlorobenzene-1,4-diamine with orthophosphoric acid, which crystallized in a non-centrosymmetric setting.

The title organic-inorganic hybrid material, while made from achiral components, crystallizes in the chiral space group P2₁2₁2₁. The crystal investigated is partially racemically twinned, with a twinning ratio of 0.89 (4) to 0.11 (4). Its structure consists of one 2-chlorobenzene-1,4-diaminium dication and two crystallographically distinct H₂PO₄^- anions (Fig. 1). The chlorine atom is disordered over two chemically equivalent positions with a small but noticable presence of the second moiety (refined value 3.29 (9)%). Associated with this disorder is disorder of one phosphate hydroxyl group of one of the H₂P(2)O₄^- anions, O6. Where not mentioned otherwise, this disorder is ignored in the following more detailed discussion of the structure.

The HPO₄^2- anions show two types of P—O distances depending on whether the oxygen atoms are hydrogen donors or acceptors. As expected, the P—OH distances, varying between 1.54 (3) and 1.581 (1) Å, are significantly longer than the other P—O distances ranging from 1.500 (1) to 1.516 (1) Å. This is in agreement with the literature data (Chtioui & Jouini, 2006; Kaabi et al., 2004). Figure 2 shows that the H₂PO₄^- anions are interconnected through O—H···O hydrogen bonds to form a two dimensional layer spreading parallel to the (0 0 1) plane at z = 0, 1/2 and 1 (Fig. 3). The organic cations, assembled in layers parallel to the H₂PO₄^- anions at z = 1/4 and 3/4, are anchored to the inorganic layers through N—H···O hydrogen bonds whose geometrical characteristics are given in Table 1. The projection of the whole arrangement along the c-axis (Fig. 3) shows the alternating cationic and anionic layers. The structure also features a weak C—Cl···O halogen bond between the chlorine atom and one of the H₂PO₄^- phosphate ions, a type of interaction that has recently attracted high levels of interest due to the observation of such interactions between halogenated compounds and the phosphate moieties in DNA (see e.g. Metrangolo & Resnati, 2008). In the title compound the Cl···O distance between Cl1 and O3ⁱ is 3.159 (2) Å, the C—Cl···O angle 140.48 (7)° (symmetry operator (i) -x + 3, y + 1/2, -z + 3/2), the equivalent values for the interaction of the minor occupied Cl atom Cl1B with O6B are 2.91 (5) Å and 130 (1)°. While the Cl···O distances are shorter than the sum of the van der Waals radii of chlorine and oxygen (ca 3.3 Å, Bondi, 1964), the angles observed are on the small side for C—Cl···O halogen bonds (160–180°, see e.g. Politzer et al., 2007; Metrangolo & Resnati, 2001), indicating that the interactions observed are quite weak and more likely a result of the stronger hydrogen bonding interactions rather than one of the major driving forces determining the outcome of the assembly of the structural components of the title compound. No π-π stacking interactions between neighboring aromatic rings or significant C—H···π interactions towards them are observed.

Related literature

For common applications of organic phosphate complexes, see: Masse et al. (1993). For network geometries, see: Rayes et al. (2004); Oueslati et al. (2005). For reference structural data, see: Kaabi et al. (2004); Chtioui & Jouini (2006). For halogen bonding, see: Metrangolo & Resnati (2001, 2008); Politzer et al. (2007). For van der Waals radii, see: Bondi (1964).

S2. Experimental

Crystals of the title compound were prepared at room temperature by slow addition of a solution of orthophosphoric acid (6 mmol in 20 ml of water) to an alcoholic solution of 2-chlorobenzene-1,4-diamine (3 mmol in 20 ml of ethanol). The acid was added until the alcoholic solution became turbid. After filtration, the solution was allowed to slowly evaporate at room temperature over several days leading to formation of transparent prismatic crystals with suitable dimensions for single-crystal structural analysis (yield 58%). The crystals are stable for months under normal conditions of temperature and humidity.

S3. Refinement

The chlorine atom is disordered over two chemically equivalent positions with a small but noticable presence of the second moiety (refined value 3.29 (9)%). Associated with this disorder is disorder of one of the phosphate hydroxyl groups, O6. The minor moiety chlorine and oxygen atoms were constrained to have the same ADPs as their major moiety counterparts. Due to the low prevalence of the minor moiety no disorder was modeled for the aromatic ring the Cl atom is bonded to, despite of the obviously unrealistic C—C—Cl angles for the minor Cl atom.

All non hydrogen atoms were refined anisotropically. All H atoms were located in difference density Fourier maps, but were then placed in calculated positions riding on their respective carrier atom with C—H distances of 0.95, N—H distances of 0.91 Å, and O—H distances of 0.84 Å. Ammonium and hydroxyl H atoms were allowed to rotate but not to tip to best fit the observed electron density distribution. The position of the hydrogen atom of the minor occupied hydroxyl group was refined with a damping factor (DAMP 2000 in SHELXTL (Sheldrick, 2008)). In the final refinement cycles after removal of the damping factor its position was set to ride on its carrier oxygen atom. U_iso(H) values were constrained to be 1.2 U_eq(C) of the parent atom for C bound H atoms, and 1.5 times U_eq(N/O) for N and O bound H atoms.

The compound was refined as a racemic twin. The twin ratio refined to 0.89 (4) to 0.11 (4).

Computing details

Data collection: APEX2 (Bruker, 2011); cell refinement: SAINT (Bruker, 2011); data reduction: SAINT (Bruker, 2011); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008) and SHELXLE (Hübschle et al., 2011); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and publCIF (Westrip, 2010).

Figures

	Fig. 1. A view of the title compound, showing 50% probability displacement ellipsoids and arbitrary spheres for the H atoms.
	Fig. 2. Projection along the c-axis of an inorganic layer in the structure of the title compound. Hydrogen bonds are denoted as red broken lines.
	Fig. 3. Projection of the structure along the b-axis. Hydrogen bonds are denoted as red broken lines, halogen bonds as black broken lines. For the disordered Cl atom, only the major part is shown.

2-Chlorobenzene-1,4-diaminium bis(dihydrogenphosphate)

Crystal data

C6H9ClN2^2+·2H2PO4^−	F(000) = 696
Mr = 338.57	Dx = 1.752 Mg m^−3
Orthorhombic, P212121	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ac 2ab	Cell parameters from 7956 reflections
a = 7.0084 (8) Å	θ = 2.6–31.8°
b = 7.9404 (9) Å	µ = 0.58 mm^−1
c = 23.064 (3) Å	T = 100 K
V = 1283.5 (3) Å^3	Block, colourless
Z = 4	0.55 × 0.52 × 0.51 mm

Data collection

Bruker SMART APEX CCD diffractometer	4134 independent reflections
Radiation source: fine-focus sealed tube	4060 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.021
ω scans	θmax = 32.0°, θmin = 2.7°
Absorption correction: multi-scan (SADABS; Bruker, 2011)	h = −6→10
Tmin = 0.689, Tmax = 0.746	k = −11→11
11671 measured reflections	l = −33→33

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.025	H-atom parameters constrained
wR(F^2) = 0.064	w = 1/[σ^2(Fo^2) + (0.0328P)^2 + 0.2706P] where P = (Fo^2 + 2Fc^2)/3
S = 1.11	(Δ/σ)max = 0.002
4134 reflections	Δρmax = 0.44 e Å^−3
186 parameters	Δρmin = −0.27 e Å^−3
0 restraints	Absolute structure: Flack (1983), 1694 Friedel pairs
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.11 (4)

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

	x	y	z	Uiso*/Ueq	Occ. (<1)
C1	1.3321 (2)	0.15359 (17)	0.76907 (6)	0.0129 (2)
H1	1.4496	0.1155	0.7849	0.015*	0.0329 (9)
C2	1.18845 (19)	0.20920 (16)	0.80593 (5)	0.0109 (2)
C3	1.0154 (2)	0.26208 (16)	0.78290 (5)	0.0131 (2)
H3	0.9161	0.2984	0.8080	0.016*
C4	0.9869 (2)	0.26197 (17)	0.72312 (5)	0.0133 (2)
H4	0.8686	0.2977	0.7072	0.016*
C5	1.13375 (19)	0.20895 (16)	0.68709 (5)	0.0108 (2)
C6	1.30604 (19)	0.15298 (17)	0.70924 (6)	0.0129 (2)
H6	1.4044	0.1149	0.6841	0.015*	0.9671 (9)
N1	1.21619 (16)	0.20932 (15)	0.86858 (4)	0.01139 (19)
H1A	1.2127	0.1016	0.8820	0.017*
H1B	1.1218	0.2704	0.8857	0.017*
H1C	1.3314	0.2560	0.8771	0.017*
N2	1.10964 (17)	0.21095 (15)	0.62440 (4)	0.01136 (19)
H2A	1.2140	0.2587	0.6076	0.017*
H2B	1.0040	0.2719	0.6151	0.017*
H2C	1.0959	0.1036	0.6112	0.017*
O1	1.22585 (15)	−0.22787 (14)	0.49473 (4)	0.01666 (19)
H1D	1.1180	−0.2666	0.4861	0.025*
O2	1.44777 (14)	−0.15775 (12)	0.57261 (4)	0.01261 (17)
O3	1.20902 (15)	−0.39458 (12)	0.58809 (4)	0.01507 (19)
H3A	1.2990	−0.4584	0.5783	0.023*
O4	1.09007 (14)	−0.10621 (12)	0.58851 (4)	0.01272 (18)
O5	1.66727 (16)	0.25284 (15)	0.50298 (4)	0.0190 (2)
H5	1.7753	0.2093	0.4981	0.029*
O6	1.64342 (16)	0.10590 (12)	0.60055 (5)	0.01469 (19)	0.9671 (9)
H6A	1.5618	0.0408	0.5861	0.022*	0.9671 (9)
O6B	1.690 (5)	0.096 (4)	0.5735 (15)	0.01469 (19)	0.0329 (9)
H6B	1.5907	0.0361	0.5728	0.022*	0.0329 (9)
O7	1.78483 (14)	0.38754 (12)	0.59744 (4)	0.01286 (18)
O8	1.43146 (14)	0.34988 (12)	0.57179 (4)	0.01380 (18)
P1	1.24379 (5)	−0.21374 (4)	0.562311 (13)	0.00959 (7)
P2	1.63262 (5)	0.28287 (4)	0.569303 (13)	0.00987 (7)
Cl1	1.54768 (5)	0.08734 (5)	0.796787 (14)	0.01984 (9)	0.9671 (9)
Cl1B	1.5045 (15)	0.0693 (15)	0.6861 (4)	0.01984 (9)	0.0329 (9)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0096 (5)	0.0148 (5)	0.0141 (5)	0.0021 (5)	−0.0011 (4)	0.0012 (4)
C2	0.0123 (5)	0.0106 (5)	0.0100 (5)	−0.0001 (5)	−0.0002 (4)	0.0011 (4)
C3	0.0119 (6)	0.0155 (5)	0.0119 (5)	0.0031 (5)	0.0008 (4)	0.0000 (4)
C4	0.0108 (6)	0.0171 (6)	0.0120 (5)	0.0040 (5)	0.0002 (4)	0.0008 (4)
C5	0.0133 (6)	0.0101 (5)	0.0091 (4)	−0.0008 (5)	0.0002 (4)	0.0000 (4)
C6	0.0105 (6)	0.0150 (5)	0.0132 (5)	0.0010 (5)	0.0010 (5)	−0.0011 (4)
N1	0.0123 (5)	0.0118 (4)	0.0100 (4)	0.0000 (4)	−0.0011 (4)	0.0004 (3)
N2	0.0123 (5)	0.0127 (4)	0.0091 (4)	−0.0006 (4)	0.0006 (4)	−0.0009 (4)
O1	0.0131 (4)	0.0260 (5)	0.0109 (4)	−0.0043 (4)	0.0005 (3)	−0.0040 (4)
O2	0.0092 (4)	0.0137 (4)	0.0150 (4)	−0.0019 (4)	−0.0006 (4)	0.0000 (3)
O3	0.0132 (5)	0.0101 (4)	0.0220 (4)	−0.0001 (4)	0.0028 (4)	0.0011 (3)
O4	0.0125 (4)	0.0111 (4)	0.0145 (4)	0.0010 (4)	0.0030 (3)	−0.0013 (3)
O5	0.0158 (5)	0.0301 (6)	0.0111 (4)	0.0048 (4)	0.0007 (4)	−0.0045 (3)
O6	0.0168 (5)	0.0097 (4)	0.0176 (5)	−0.0014 (4)	−0.0033 (4)	0.0011 (3)
O6B	0.0168 (5)	0.0097 (4)	0.0176 (5)	−0.0014 (4)	−0.0033 (4)	0.0011 (3)
O7	0.0129 (4)	0.0110 (4)	0.0146 (4)	−0.0013 (4)	−0.0023 (3)	−0.0019 (3)
O8	0.0105 (4)	0.0142 (4)	0.0167 (4)	0.0011 (4)	0.0007 (4)	0.0000 (3)
P1	0.00924 (14)	0.00981 (12)	0.00974 (12)	−0.00071 (12)	0.00054 (11)	−0.00102 (11)
P2	0.00882 (14)	0.00994 (12)	0.01085 (13)	0.00014 (12)	−0.00035 (11)	−0.00110 (11)
Cl1	0.01175 (15)	0.03455 (19)	0.01321 (14)	0.00876 (14)	−0.00169 (12)	0.00062 (13)
Cl1B	0.01175 (15)	0.03455 (19)	0.01321 (14)	0.00876 (14)	−0.00169 (12)	0.00062 (13)

Geometric parameters (Å, º)

C1—C2	1.3898 (18)	N2—H2B	0.9100
C1—C6	1.3921 (17)	N2—H2C	0.9100
C1—Cl1	1.7228 (14)	O1—P1	1.5678 (10)
C1—H1	0.9500	O1—H1D	0.8400
C2—C3	1.3889 (18)	O2—P1	1.5159 (10)
C2—N1	1.4578 (14)	O3—P1	1.5731 (10)
C3—C4	1.3933 (17)	O3—H3A	0.8400
C3—H3	0.9500	O4—P1	1.5016 (10)
C4—C5	1.3879 (18)	O5—P2	1.5670 (10)
C4—H4	0.9500	O5—H5	0.8400
C5—C6	1.3843 (18)	O6—P2	1.5811 (11)
C5—N2	1.4558 (14)	O6—H6A	0.8400
C6—Cl1B	1.631 (10)	O6—H6B	0.9243
C6—H6	0.9500	O6B—P2	1.54 (3)
N1—H1A	0.9100	O6B—H6B	0.8400
N1—H1B	0.9100	O7—P2	1.5000 (10)
N1—H1C	0.9100	O8—P2	1.5080 (10)
N2—H2A	0.9100
C2—C1—C6	120.83 (12)	C5—N2—H2A	109.5
C2—C1—Cl1	120.36 (10)	C5—N2—H2B	109.5
C6—C1—Cl1	118.81 (10)	H2A—N2—H2B	109.5
C2—C1—H1	119.6	C5—N2—H2C	109.5
C6—C1—H1	119.6	H2A—N2—H2C	109.5
C3—C2—C1	119.64 (11)	H2B—N2—H2C	109.5
C3—C2—N1	119.69 (11)	P1—O1—H1D	109.5
C1—C2—N1	120.65 (11)	P1—O3—H3A	109.5
C2—C3—C4	120.22 (12)	P2—O5—H5	109.5
C2—C3—H3	119.9	P2—O6—H6A	109.5
C4—C3—H3	119.9	P2—O6—H6B	101.4
C5—C4—C3	119.11 (12)	P2—O6B—H6B	109.2
C5—C4—H4	120.4	O4—P1—O2	116.53 (6)
C3—C4—H4	120.4	O4—P1—O1	112.54 (6)
C6—C5—C4	121.54 (11)	O2—P1—O1	104.62 (6)
C6—C5—N2	118.11 (11)	O4—P1—O3	104.82 (5)
C4—C5—N2	120.34 (11)	O2—P1—O3	110.77 (6)
C5—C6—C1	118.63 (12)	O1—P1—O3	107.34 (6)
C5—C6—Cl1B	138.9 (4)	O7—P2—O8	116.93 (6)
C1—C6—Cl1B	102.3 (4)	O7—P2—O6B	108.8 (12)
C5—C6—H6	120.7	O8—P2—O6B	125.5 (13)
C1—C6—H6	120.7	O7—P2—O5	113.36 (6)
C2—N1—H1A	109.5	O8—P2—O5	103.63 (6)
C2—N1—H1B	109.5	O6B—P2—O5	82.8 (13)
H1A—N1—H1B	109.5	O7—P2—O6	105.14 (6)
C2—N1—H1C	109.5	O8—P2—O6	109.93 (6)
H1A—N1—H1C	109.5	O5—P2—O6	107.60 (6)
H1B—N1—H1C	109.5

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1A···O7^i	0.91	1.76	2.6726 (15)	175
N1—H1B···O4^ii	0.91	1.88	2.7807 (15)	172
N1—H1C···O2^iii	0.91	2.05	2.9155 (15)	158
N2—H2A···O8	0.91	1.88	2.7886 (15)	178
N2—H2B···O7^iv	0.91	1.84	2.7450 (15)	178
N2—H2C···O4	0.91	1.75	2.6545 (15)	175
O1—H1D···O2^v	0.84	1.90	2.6525 (14)	148
O3—H3A···O8^vi	0.84	1.79	2.5863 (14)	158
O5—H5···O8^vii	0.84	2.00	2.6585 (14)	134
O6—H6A···O2	0.84	1.79	2.5841 (14)	156
O6B—H6B···O2	0.84	1.84	2.63 (3)	157

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