4-Aza-1-azoniabi­cyclo­[2.2.2]­octane di­hydrogenphosphite

The title compound, C₆H₁₃N⁺·H₂PO₃⁻, contains monoproton­ated 4-aza-1-azoniabi­cyclo­[2.2.2]­octane (dabconium, C₆H₁₃N⁺) cations and di­hydrogenphosphite (H₂PO₃⁻) anions. The H₂PO₃⁻ units are linked into a polymeric chain by P—O—H...O—P hydrogen bonds in the [100] direction. The dabconium cations are pendant to the di­hydrogenphosphite chains by way of N—H...O hydrogen bonds and possible C—H...O interactions. The chains are crosslinked by means of van der Waals forces.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.004 Å
• R factor = 0.037
• wR factor = 0.098
• Data-to-parameter ratio = 19.4

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT241_ALERT_2_C Check High   U(eq) as Compared to Neighbors ....         C4
PLAT242_ALERT_2_C Check Low    U(eq) as Compared to Neighbors ....         N1
PLAT242_ALERT_2_C Check Low    U(eq) as Compared to Neighbors ....         P1

Alert level G
REFLT03_ALERT_4_G 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.
           From the CIF: _diffrn_reflns_theta_max           27.50
           From the CIF: _reflns_number_total               2139
           Count of symmetry unique reflns         1258
           Completeness (_total/calc)            170.03%
           TEST3: Check Friedels for noncentro structure
           Estimate of Friedel pairs measured       881
           Fraction of Friedel pairs measured     0.700
           Are heavy atom types Z>Si present          yes

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

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   3 ALERT type 2 Indicator that the structure model may be wrong or deficient
   0 ALERT type 3 Indicator that the structure quality may be low
   1 ALERT type 4 Improvement, methodology, query or suggestion

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S1. Comment

The crystal structures of amine (hydrogen) phosphites containing HPO₃²⁻ or H₂PO₃⁻ ions are of interest in terms of the interplay between cation–anion and anion–anion hydrogen bonds and for comparison with their phosphate (HPO₄²⁻ or H₂PO₄⁻) analogues (Averbuch-Pouchot, 1993a,b). Previous reports of phosphite-containing crystal structures have been recently surveyed by Idrissi et al. (2002).

The structure of (I) (Fig. 1) consists of monoprotonated 4-aza-1-azoniabicyclo[2.2.2]octane (dabconium, C₆H₁₃N⁺) cations and dihydrogenphosphite (H₂PO₃⁻) anions. The dabconium cation has typical (Bremner & Harrison, 2003) geometrical parameters [d_av(N—C) = 1.470 (3) Å, d_av(C—C) = 1.528 (3) Å and θ_av(C—N—C) = 109.1 (2)°]. The (HN1)⁺—C—C bond angles [θ_av= 108.2 (2)°] are significantly smaller than the equivalent N2—C—C values [θ_av= 111.1 (2)°]. The dihydrogenphosphite group shows its usual (Idrissi et al., 2002) pseudo-pyramidal geometry [d_av(P—O) = 1.508 (2) Å and θ_av(O—P—O) = 111.9 (2)°]. The protonated P–O1 vertex shows its expected lengthening relative to the other P—O bonds and the unprotonated O2—P1—O3 bond angle (Table 1) is notably larger than the corresponding O—P—OH angles, as seen previously for the same anion in related compounds (Avebuch-Pouchot, 1993a,b; Harrison 2003b).

Apart from electrostatic forces, the component species in (I) interact by means of O—H···O and N—H···O hydrogen bonds (Table 2), and possibly a C—H···O interaction (see below). The H₂PO₃ units are linked into a polymeric chain by P—O—H···O—P hydrogen bonds in the [100] direction (Fig. 2), resulting in a P1···P1ⁱ [symmetry code: (i) 1/2 + x, 3/2 − y, 1 − z] separation of 4.7846 (8) Å. Similar inter-anion linkages have been seen in a number of amine phosphites, for example, isopropylammonium dihydrogenphosphite, (C₃H₁₀N)(H₂PO₃) (Avebuch-Pouchot, 1993a), guanidinium dihydrogenphosphite, (CH₆N₃)(H₂PO₃) (Harrison, 2003a), and triethanolammonium dihydrogenphosphite, (C₆H₁₆NO₃)(H₂PO₃) (Harrison, 2003b). In all these cases, a 2₁ screw axis generates the dihydrogenphosphite chain from a single distinct H₂PO₃⁻ moiety. The organic species are pendant to the chains by way of the N1—H3···O2 hydrogen bonds. A short C2—H6···O2ⁱⁱ [symmetry code: (ii) 1 − x, y, z] interaction was identified in a PLATON (Spek, 2003) analysis of the structure [d(C—H) = 0.97 Å, d(H···O) = 2.53 Å, d(C···O) = 3.450 (3) Å and θ(C—H···O) = 157.8°]. If it is not merely a packing artefact, it may provide some additional coherence betweeen the phosphite backbone and the pendant dabconium cations (Fig. 2). Inter-chain connectivity normal to [110] (Fig. 3) is mediated by van der Waals forces.

S2. Experimental

H₃PO₃ (0.82 g, 1 mmol) and dabco (1,4-dianoniabicyclo[2.2.2]octane, C₈H₁₂N₂; 1.12 g, 1 mmol) were dissolved in 20 ml deionized water, giving a clear solution. Slab- and block-shaped crystals of (I) grew as the water evaporated from the increasingly viscous liquors over the course of several weeks. These colourless transparent crystals were washed with acetone and dried in air. The same phase, adopting a more platy morphology, can also be crystallized from a 1:1 mixture of H₃PO₃ and dabco in methanol.

S3. Refinement

The O—H hydrogen atom was found in a difference map and refined by riding in its as-found position. The N—H hydrogen atom was found in a difference map and refined by riding in an idealized position [d(N—H) = 0.91 Å]. H atoms bonded to C and P atoms were placed in calculated positions [d(C—H) = 0.97 Å and d(P—H) = 1.32 Å] and refined by riding. For all H atoms, the constraint U_iso(H) = 1.2U_eq(parent atom) was applied.

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. View of (I) (30% displacement ellipsoids). H atoms are drawn as small spheres of arbitrary radius and hydrogen bonds are indicated by dashed lines. All C—H H atoms have been omitted for clarity.
	Fig. 2. Detail of a [100] dihydrogen phosphite chain and pendant dabconium cations in (I). Colour key: [H2PO3]^− tetrahedra yellow, O atoms red, C atoms blue, N atoms green, H atoms grey (all radii arbitrary). The H···O portions of the N—H···O hydrogen bonds and C—H···O interactions are highlighted in yellow and light blue, respectively. All C—H H atoms except H5 have been omitted for clarity.
	Fig. 3. [010] projection of (I). Colour key as in Fig. 2. A l l C—H H atoms except H5 have been omitted for clarity.

4-Aza-1-azoniabicyclo[2.2.2]octane dihydrogenphosphite

Crystal data

C6H13N2^+·H2O3P^−	F(000) = 416
Mr = 194.17	Dx = 1.389 Mg m^−3
Orthorhombic, P212121	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ac 2ab	Cell parameters from 3200 reflections
a = 6.6418 (4) Å	θ = 2.5–27.3°
b = 9.9428 (6) Å	µ = 0.27 mm^−1
c = 14.0575 (8) Å	T = 293 K
V = 928.33 (10) Å^3	Slab, colourless
Z = 4	0.45 × 0.15 × 0.07 mm

Data collection

Bruker SMART1000 CCD diffractometer	2139 independent reflections
Radiation source: fine-focus sealed tube	1861 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.028
ω scans	θmax = 27.5°, θmin = 2.5°
Absorption correction: multi-scan (SADABS; Bruker, 1999)	h = −7→8
Tmin = 0.886, Tmax = 0.990	k = −10→12
6962 measured reflections	l = −18→17

Refinement

Refinement on F^2	Hydrogen site location: difmap (O-H, N-H) and geom (C-H, P-H)
Least-squares matrix: full	H-atom parameters constrained
R[F^2 > 2σ(F^2)] = 0.037	w = 1/[σ^2(Fo^2) + (0.0606P)^2 + 0.0257P] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.098	(Δ/σ)max = 0.001
S = 1.04	Δρmax = 0.23 e Å^−3
2139 reflections	Δρmin = −0.26 e Å^−3
110 parameters	Absolute structure: Flack (1983), 881 Friedel pairs
0 restraints	Absolute structure parameter: 0.15 (12)
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	0.72109 (8)	0.62955 (5)	0.58804 (4)	0.04115 (15)
H1	0.6694	0.5401	0.5231	0.049*
O1	0.9539 (2)	0.64524 (19)	0.58243 (12)	0.0655 (5)
H2	1.0090	0.6853	0.5241	0.079*
O2	0.6770 (3)	0.5684 (2)	0.68263 (12)	0.0697 (6)
O3	0.6123 (3)	0.75504 (19)	0.56514 (13)	0.0698 (5)
N1	0.3717 (3)	0.61178 (18)	0.79192 (12)	0.0432 (4)
H3	0.4784	0.6026	0.7518	0.052*
N2	0.0775 (3)	0.63634 (19)	0.90403 (15)	0.0540 (4)
C1	0.2246 (4)	0.5024 (2)	0.77401 (16)	0.0515 (5)
H4	0.2900	0.4156	0.7800	0.062*
H5	0.1708	0.5101	0.7101	0.062*
C2	0.0544 (4)	0.5145 (2)	0.84689 (19)	0.0597 (6)
H6	−0.0740	0.5168	0.8141	0.072*
H7	0.0555	0.4364	0.8882	0.072*
C3	0.4417 (4)	0.6009 (3)	0.89150 (17)	0.0682 (8)
H8	0.5471	0.6663	0.9035	0.082*
H9	0.4959	0.5118	0.9031	0.082*
C4	0.2638 (5)	0.6269 (4)	0.95691 (18)	0.0770 (8)
H10	0.2537	0.5544	1.0029	0.092*
H11	0.2858	0.7100	0.9915	0.092*
C5	0.2721 (5)	0.7432 (2)	0.7746 (2)	0.0652 (7)
H12	0.2341	0.7510	0.7082	0.078*
H13	0.3634	0.8162	0.7899	0.078*
C6	0.0845 (4)	0.7503 (2)	0.8380 (2)	0.0652 (7)
H14	0.0860	0.8337	0.8738	0.078*
H15	−0.0352	0.7498	0.7985	0.078*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
P1	0.0450 (3)	0.0391 (2)	0.0394 (2)	0.0019 (2)	−0.0010 (2)	0.0008 (2)
O1	0.0491 (9)	0.0900 (13)	0.0575 (9)	0.0011 (9)	0.0012 (8)	0.0288 (11)
O2	0.0639 (12)	0.0796 (12)	0.0657 (11)	0.0160 (10)	0.0243 (9)	0.0282 (10)
O3	0.0758 (13)	0.0634 (10)	0.0702 (12)	0.0191 (9)	−0.0149 (9)	0.0115 (9)
N1	0.0410 (8)	0.0435 (9)	0.0450 (8)	0.0003 (7)	0.0036 (7)	0.0014 (8)
N2	0.0542 (10)	0.0473 (10)	0.0607 (10)	0.0074 (9)	0.0144 (9)	0.0016 (11)
C1	0.0593 (14)	0.0393 (10)	0.0558 (12)	−0.0046 (10)	0.0007 (11)	−0.0043 (9)
C2	0.0515 (14)	0.0450 (12)	0.0825 (17)	−0.0061 (10)	0.0080 (13)	0.0028 (12)
C3	0.0520 (14)	0.097 (2)	0.0553 (13)	−0.0019 (13)	−0.0110 (10)	−0.0049 (14)
C4	0.0820 (19)	0.103 (2)	0.0457 (12)	0.0073 (19)	−0.0005 (13)	−0.0099 (15)
C5	0.0828 (19)	0.0349 (10)	0.0778 (16)	0.0053 (12)	0.0222 (15)	0.0121 (11)
C6	0.0681 (16)	0.0369 (12)	0.0908 (19)	0.0101 (11)	0.0117 (15)	0.0019 (13)

Geometric parameters (Å, º)

P1—O3	1.4774 (19)	C1—H5	0.9700
P1—O2	1.4910 (16)	C2—H6	0.9700
P1—O1	1.5561 (18)	C2—H7	0.9700
P1—H1	1.3200	C3—C4	1.519 (4)
O1—H2	0.9825	C3—H8	0.9700
N1—C3	1.479 (3)	C3—H9	0.9700
N1—C1	1.483 (3)	C4—H10	0.9700
N1—C5	1.485 (3)	C4—H11	0.9700
N1—H3	0.9100	C5—C6	1.534 (4)
N2—C4	1.447 (4)	C5—H12	0.9700
N2—C2	1.462 (3)	C5—H13	0.9700
N2—C6	1.465 (3)	C6—H14	0.9700
C1—C2	1.530 (3)	C6—H15	0.9700
C1—H4	0.9700
O3—P1—O2	116.25 (11)	C1—C2—H7	109.5
O3—P1—O1	112.98 (12)	H6—C2—H7	108.1
O2—P1—O1	106.34 (10)	N1—C3—C4	108.4 (2)
O3—P1—H1	106.9	N1—C3—H8	110.0
O2—P1—H1	106.9	C4—C3—H8	110.0
O1—P1—H1	106.9	N1—C3—H9	110.0
P1—O1—H2	117.0	C4—C3—H9	110.0
C3—N1—C1	108.32 (19)	H8—C3—H9	108.4
C3—N1—C5	111.1 (2)	N2—C4—C3	111.43 (19)
C1—N1—C5	108.90 (19)	N2—C4—H10	109.3
C3—N1—H3	109.5	C3—C4—H10	109.3
C1—N1—H3	109.5	N2—C4—H11	109.3
C5—N1—H3	109.5	C3—C4—H11	109.3
C4—N2—C2	108.5 (2)	H10—C4—H11	108.0
C4—N2—C6	110.4 (2)	N1—C5—C6	107.86 (18)
C2—N2—C6	107.24 (19)	N1—C5—H12	110.1
N1—C1—C2	108.39 (17)	C6—C5—H12	110.1
N1—C1—H4	110.0	N1—C5—H13	110.1
C2—C1—H4	110.0	C6—C5—H13	110.1
N1—C1—H5	110.0	H12—C5—H13	108.4
C2—C1—H5	110.0	N2—C6—C5	111.02 (19)
H4—C1—H5	108.4	N2—C6—H14	109.4
N2—C2—C1	110.81 (19)	C5—C6—H14	109.4
N2—C2—H6	109.5	N2—C6—H15	109.4
C1—C2—H6	109.5	C5—C6—H15	109.4
N2—C2—H7	109.5	H14—C6—H15	108.0

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H2···O3^i	0.98	1.55	2.528 (2)	176
N1—H3···O2	0.91	1.67	2.580 (2)	174

Symmetry code: (i) x+1/2, −y+3/2, −z+1.