Bis(oxonium) tetra­kis(o-toluidinium) cyclo­hexa­phosphate

Houda Marouani; Mohamed Rzaigui; Salem S Al-Deyab

doi:10.1107/S1600536810006537

. 2010 Feb 27;66(Pt 3):o702. doi: 10.1107/S1600536810006537

Bis(oxonium) tetrakis(o-toluidinium) cyclohexaphosphate

Houda Marouani ^a,^*, Mohamed Rzaigui ^a, Salem S Al-Deyab ^b

PMCID: PMC2983635 PMID: 21580440

Abstract

In the title compound, 4C₇H₁₀N⁺·2H₃O⁺·P₆O₁₈ ⁶⁻, the complete cyclohexaphosphate anion is generated by crystallographic inversion symmetry. In the crystal, the H₃O⁺ ions and the [P₆O₁₈]⁶⁻ anions are linked by O—H⋯O hydrogen bonds, generating infinite layers lying parallel to the ab plane at z = 1/2. These layers are interconnected by the organic cations, which establish N—H⋯O hydrogen bonds with the [P₆O₁₈]⁶⁻ anions.

Related literature

For further synthetic details, see: Schülke & Kayser (1985 ▶). For related structures, see: Amri et al. (2008 ▶); Larafa et al. (1997 ▶); Akriche & Rzaigui (2000 ▶); Selmi et al. (2009 ▶); Khemiri et al. (2009 ▶). For a discussion on hydrogen bonding, see: Brown (1976 ▶); Blessing (1986 ▶). For tetrahedral distortions, see: Baur (1974 ▶).

Experimental

Crystal data

4C₇H₁₀N⁺·2H₃O⁺·P₆O₁₈ ⁶⁻
M _r = 944.51
Triclinic,
a = 9.344 (3) Å
b = 10.360 (2) Å
c = 11.537 (2) Å
α = 95.35 (4)°
β = 92.23 (3)°
γ = 116.00 (5)°
V = 995.4 (4) Å³
Z = 1
Mo Kα radiation
μ = 0.36 mm⁻¹
T = 293 K
0.25 × 0.20 × 0.15 mm

Data collection

Enraf–Nonius CAD-4 diffractometer
6038 measured reflections
5773 independent reflections
3061 reflections with I > 2σ(I)
R _int = 0.025
2 standard reflections every 120 min intensity decay: 10%

Refinement

R[F ² > 2σ(F ²)] = 0.052
wR(F ²) = 0.114
S = 1.01
5773 reflections
278 parameters
6 restraints
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.33 e Å⁻³
Δρ_min = −0.38 e Å⁻³

Data collection: CAD-4 EXPRESS (Enraf–Nonius, 1994 ▶); cell refinement: CAD-4 EXPRESS; data reduction: XCAD4 (Harms & Wocadlo, 1996 ▶); program(s) used to solve structure: SHELXS86 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEP-3 (Farrugia, 1997 ▶); software used to prepare material for publication: WinGX (Farrugia, 1999 ▶).

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536810006537/hb5337sup1.cif

e-66-0o702-sup1.cif^{(19.3KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810006537/hb5337Isup2.hkl

e-66-0o702-Isup2.hkl^{(276.9KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O10—H110⋯O9	0.86 (1)	1.62 (1)	2.469 (3)	170 (3)
O10—H210⋯O2ⁱ	0.86 (1)	1.69 (1)	2.550 (3)	177 (3)
O10—H310⋯O6ⁱⁱ	0.86 (1)	1.67 (1)	2.524 (3)	171 (3)
N1—H1A⋯O8ⁱⁱⁱ	0.89	1.86	2.753 (3)	177
N1—H1B⋯O2ⁱ	0.89	1.98	2.853 (3)	168
N1—H1C⋯O5ⁱⁱⁱ	0.89	1.92	2.800 (3)	169
N2—H2A⋯O6^iv	0.89	2.35	3.085 (4)	140
N2—H2B⋯O5ⁱⁱ	0.89	2.02	2.904 (3)	176
N2—H2C⋯O1^v	0.89	1.83	2.710 (3)	170

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) ; (iv) ; (v) .

supplementary crystallographic information

Comment

Many cyclohexaphosphates of organic cations and inorganic cations (mono, bi and trivalent) have been synthesized and structurally characterized. But the association of the oxonium cation to this kind of material is very rare. On the other hand, there is only one cyclohexaphosphate of mixed cation (organic-oxonium) (Amri, et al., 2008). In this work, we report the preparation and the structural investigation of a new organic oxonium cyclohexaphospohate, (o-CH₃C₆H₄NH₃)₄(H₃O)₂P₆O₁₈, (I).

The title compound is built up from P₆O₁₈^6- anion, four organic o-toluidinium and two oxonium cations (Fig. 1). The half of the anion, two organic and one oxonium cations constitute the asymmetric unit of (I). The atomic arrangement of the title compound is characterized by the existence of inorganic layers, built by P₆O₁₈^6- ring anions and oxonium cations. Each cyclohexaphosphate group is connected to its adjacent neighbours by six oxonium ions through strong O—H···O hydrogen bonds (Table 1) (H···O = 1.66 Å) (Blessing, 1986); (Brown, 1976). The same phenomenon has been observed for (C₁₀H₁₃NH₃)₄(H₃O)₂P₆O₁₈.3H₂O (Amri, et al., 2008).

It is worth noting that the H₃O⁺ ions exhibit a pyramidal geometry. These layers formed by P₆O₁₈ groups and oxonium ions cross the unit cell parallel to the (a, b) plane at z = 1/2 (Fig. 2). Between these layers, separated by a distance of 11.537 (2) Å, organic cations establish hydrogen bonds to interconnect the different anions. The N(1)H₃ groups produce the internal P₆O₁₈ ring cohesion through hydrogen bonds involving external oxygen atoms of each PO₄ tetrahedron. The other N(2)H₃ groups, link three different rings and so contribute to the interlayer cohesion of this compound. Inside such a structure, the phosphoric ring has an -1 internal symmetry. It develops around the inversion centre located at (0, 0, 1/2), so it is built up by only three independent tetrahedra. The calculated average values of the distortion indices (Baur, 1974) corresponding to the different angles and distances in the PO₄ tetrahedra [DI (OPO) = 0.038; DI (PO) = 0.039; and DI (OO) = 0.012], show a pronounced distortion of the PO distances and OPO angles if compared to OO distances. So, the PO₄ group can be considered as a rigid regular arrangement of oxygen atoms, with the phosphorus atom slightly displaced from the gravity centre.

In this atomic arrangement exist two independent o-toluidinium cations. Interatomic bond lengths and angles of these groups spread respectively within the ranges [1.367 (5)-1.504 (4) Å] and [115.7 (3)-122.8 (3)°]. The aromatic rings are planar with an average deviation of 0.000189 Å and form a dihedral angle of 28.53°. These values are similar to those obtained for the same organic group in other compounds (Larafa, et al. 1997); (Akriche & Rzaigui, 2000); (Selmi, et al., 2009); (Khemiri et al., 2009).

Experimental

The title compound has been prepared in two steps. In the first one, we prepare Li₆P₆O₁₈.6H₂O according to the process described by Schülke and Kayser (Schülke & Kayser, 1985). From this lithium salt, we prepare an aqueous solution of cyclohexaphosphate acid H₆P₆O₁₈ by passing a solution of Li₆P₆O₁₈.6H₂O (5 g in 100 ml) through an ion- exchange resin in its H-state (Amberlite IR 120). In the second step, at 20 ml of the aqueous solution of H₆P₆O₁₈ freshly prepared, we add drop by drop a solution of o-toluidine (30 mmol in 20 ml of ethanol) under continuous stirring.

In order to avoid the hydrolysis of the ring anion the above reaction is performed at room temperature. The so-obtained solution is then slowly evaporated until1 the formation of pink prisms of (I). The title compound is stable for months under normal conditions of temperature and relative humidity.