Piperizinium hydrogen phosphite monohydrate

The title compound, C₆H₁₂N₂²⁺·HPO₃²⁻·H₂O, contains doubly protonated piperizinium cations, hydrogen phosphite anions and water mol­ecules. The component species have normal geometrical parameters and interact by way of N—H⋯O and O—H⋯O hydrogen bonds, resulting in [010] chains of alternating [HPO₃]²⁻ and H₂O species, crosslinked by the organic moieties. A possible C—H⋯O interaction is also present.

Comment

The crystal structures of (protonated) amine hydrogen phosphites containing [HPO₃]²⁻ or [H₂PO₃]⁻ oxo-anions are of crystallochemical interest in terms of the interplay between the hydrogen bonds linking the cations, anions, and, if applicable, water mol­ecules together (Averbuch-Pouchot, 1993a,b; Harrison, 2003a,b).

The asymmetric unit of the title compound, (I), consists of two half-mol­ecule {C₂H₆N} fragments of (C₄H₁₂N₂)²⁺ piperizinium cations, an [HPO₃]²⁻ hydrogen phosphite group and a water mol­ecule. Inversion symmetry (Fig. 1) generates the two complete piperizinium cations, and the water O atom is disordered over two adjacent sites (see Experimental). The ­hydrogen phosphite group shows its usual (Harrison, 2003a) pseudo-pyramidal geometry [mean d(P—O) = 1.521 (2) Å; mean θ(O—P—O) = 112.48 (9)°] and the organic species adopt typical chair conformations.

As well as 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). Infinite chains of alternating [HPO₃]²⁻ and H₂O moieties are formed (Fig. 2) along [010] as a result of the water-to-phosphite O—H⋯O hydrogen bonds, with the repeating units generated by translation symmetry. The resulting P1⋯P1ⁱⁱ (Fig. 2; see Table 2 for symmetry code) separation of 6.5706 (7) Å is naturally much larger than the typical P⋯P separations (4.7–4.9 Å) seen when [H₂PO₃]⁻ di­hydrogen phosphite units link together by way of P—O—H⋯O—P interactions without an intervening water mol­ecule (Averbuch-Pouchot, 1993a, Harrison, 2003a).

The piperizinium cations crosslink the [010] [HPO₃]²⁻–H₂O chains by way of the N—H⋯O hydrogen bonds (Table 2), with all four bonds close to linear [mean θ(N—H⋯O) = 168°]. A short C1—H5⋯O4a^iv (Table 2) interaction was identified in a PLATON (Spek, 2003) analysis of (I). If it is not merely a packing artefact, it may provide some additional coherence between the piperizinium cations and the water component of the [HPO₃]²⁻–H₂O [010] chains, although its role, if any, in the disordering of the water mol­ecule O4 atom is not obvious.

Figure 1 View of (I) (50% displacement ellipsoids; H atoms are drawn as small spheres of arbitrary radius). The disordered O4b species is omitted. Symmetry codes: (i) −x, 1 − y, −z; (ii) 1 − x, 1 − y, −z.

Figure 2 Detail of a [010] hydrogen phosphite–water chain with the H⋯O components of the hydrogen bonds indicated by dashed lines (atom O4b not shown). Symmetry codes: (i) x, y + 1, z; (ii) x, y − 1, z.

Figure 3 Unit-cell packing in (I) projected onto (010). The H⋯O components of the hydrogen bonds are indicated by dashed lines. O4b and all C—H H atoms are omitted for clarity.

Experimental

H₃PO₃ (0.82 g; 1 mmol) and piperizine hexahydrate (1.92 g; 0.01 mmol) were dissolved in 10 ml deionized water, resulting in a clear solution. Block-shaped crystals of (I) grew as the water evaporated over several days.

Crystal data

• C₆H₁₂N₂²⁺·HPO₃²⁻·H₂O

• M_r = 186.15

• Monoclinic, P2₁/c

• a = 12.2476 (8) Å

• b = 6.5706 (4) Å

• c = 10.6592 (8) Å

• β = 92.744 (1)°

• V = 856.8 (1) ų

• Z = 4

• D_x = 1.443 Mg m⁻³

• Mo Kα radiation

• Cell parameters from 2470 reflections

• θ = 3.3–29.8°

• μ = 0.30 mm⁻¹

• T = 293 (2) K

• Block, colourless

• 0.27 × 0.23 × 0.19 mm

Data collection

• Bruker SMART1000 CCD diffractometer

• ω scans

• Absorption correction: multi-scan (SADABS; Bruker, 1999) T_min = 0.925, T_max = 0.949

• 6211 measured reflections

• 2468 independent reflections

• 1930 reflections with I > 2σ(I)

• R_int = 0.022

• θ_max = 30.0°

• h = −17 → 16

• k = −8 → 9

• l = −14 → 12

Refinement

• Refinement on F²

• R[F² > 2σ(F²)] = 0.042

• wR(F²) = 0.131

• S = 1.02

• 2468 reflections

• 100 parameters

• H-atom parameters constrained

• w = 1/[σ²(F_o²) + (0.0845P)²] where P = (F_o² + 2F_c²)/3

• (Δ/σ)_max < 0.001

• Δρ_max = 0.78 e Å⁻³

• Δρ_min = −0.44 e Å⁻³

Table 1
Selected bond lengths (Å) for (I)

P1—O3	1.5151 (13)
P1—O2	1.5230 (12)
P1—O1	1.5234 (14)

Table 2
Hydrogen-bonding geometry (Å, °) for (I)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H2⋯O2^i	0.90	1.84	2.7147 (19)	164
N1—H3⋯O2^ii	0.90	1.81	2.7043 (19)	172
N2—H8⋯O3^ii	0.90	1.77	2.642 (2)	163
N2—H9⋯O1^iii	0.90	1.78	2.676 (2)	171
O4a—H14⋯O1	0.95	1.90	2.840 (4)	167
O4a—H15⋯O3^ii	0.93	1.90	2.811 (4)	168
O4b—H14⋯O1	0.93	1.90	2.752 (4)	151
O4b—H15⋯O3^ii	0.96	1.90	2.765 (4)	149
C1—H5⋯O4a^iv	0.97	2.38	3.300 (5)	159
Symmetry codes: (i) ; (ii) x,1+y,z; (iii) ; (iv) .

The water O atom was modelled as being disordered over two adjacent sites with isotropic displacement factors [d(O4a⋯O4b) = 0.638 (5) Å; fractional site occupancies = 0.563 (14) and 0.437 (14) for O4a and O4b, respectively, with their sum constrained to unity]. The present data did not reveal H-atom sites that could be unambiguously associated with either O4a or O4b; instead, two distinct features in the difference map provided H-atom sites that were reasonable for both O4a and O4b (see Table 2). These O—H H atoms were refined by riding on O4a in their as-found positions. The N—H H atoms were found in difference maps and refined by riding in their idealized positions [d(N—H) = 0.90 Å]. The H atoms bonded to C and P were placed in calculated positions [d(C—H) = 0.97 Å; d(P—H) = 1.32 Å] and refined by riding. For all H atoms, the constraint U_iso(H) = 1.2U_eq(carrier atom) was applied.

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); software used to prepare material for publication: SHELXL97.

Supporting information

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); software used to prepare material for publication: SHELXL97.

(I)

Crystal data

(C6H12N2)^2+·[HPO3]^2^−·H2O	F(000) = 400
Mr = 186.15	Dx = 1.443 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 2470 reflections
a = 12.2476 (8) Å	θ = 3.3–29.8°
b = 6.5706 (4) Å	µ = 0.30 mm^−1
c = 10.6592 (8) Å	T = 293 K
β = 92.744 (1)°	Block, colourless
V = 856.8 (1) Å^3	0.27 × 0.23 × 0.19 mm
Z = 4

Data collection

Bruker SMART1000 CCD diffractometer	2468 independent reflections
Radiation source: normal-focus sealed tube	1930 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.022
ω scans	θmax = 30.0°, θmin = 3.3°
Absorption correction: multi-scan (SADABS; Bruker, 1999)	h = −17→16
Tmin = 0.925, Tmax = 0.949	k = −8→9
6211 measured reflections	l = −14→12

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)] = 0.042	Hydrogen site location: difmap (O-H and N-H) and geom (C-H and P-H)
wR(F^2) = 0.131	H-atom parameters constrained
S = 1.02	w = 1/[σ^2(Fo^2) + (0.0845P)^2] where P = (Fo^2 + 2Fc^2)/3
2468 reflections	(Δ/σ)max < 0.001
100 parameters	Δρmax = 0.78 e Å^−3
0 restraints	Δρmin = −0.44 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	Occ. (<1)
P1	0.23916 (3)	−0.02316 (6)	0.23270 (4)	0.02544 (15)
H1	0.2609	0.0944	0.1366	0.031*
O1	0.27883 (11)	0.0919 (2)	0.35030 (14)	0.0398 (3)
O2	0.11571 (10)	−0.0529 (2)	0.22692 (13)	0.0335 (3)
O3	0.30154 (11)	−0.2194 (2)	0.21505 (14)	0.0420 (4)
N1	0.01729 (11)	0.6267 (2)	0.10922 (13)	0.0272 (3)
H2	−0.0364	0.5840	0.1576	0.033*
H3	0.0549	0.7250	0.1512	0.033*
C1	−0.03148 (15)	0.7113 (3)	−0.01021 (17)	0.0318 (4)
H4	0.0258	0.7674	−0.0596	0.038*
H5	−0.0817	0.8203	0.0082	0.038*
C2	0.09189 (15)	0.4532 (3)	0.08474 (18)	0.0321 (4)
H6	0.1205	0.3975	0.1639	0.039*
H7	0.1530	0.5012	0.0383	0.039*
N2	0.39969 (11)	0.5910 (2)	0.03315 (15)	0.0339 (4)
H8	0.3613	0.6719	0.0831	0.041*
H9	0.3531	0.5391	−0.0264	0.041*
C3	0.48414 (15)	0.7131 (3)	−0.0271 (2)	0.0377 (4)
H10	0.5317	0.7769	0.0368	0.045*
H11	0.4496	0.8195	−0.0780	0.045*
C4	0.44956 (15)	0.4235 (3)	0.10849 (19)	0.0372 (4)
H12	0.3926	0.3446	0.1458	0.045*
H13	0.4964	0.4794	0.1759	0.045*
O4A	0.2172 (5)	0.5036 (5)	0.3865 (3)	0.0557 (14)*	0.563 (14)
H14	0.2488	0.3733	0.3721	0.067*
H15	0.2536	0.5828	0.3296	0.067*
O4B	0.2678 (6)	0.5011 (6)	0.4032 (4)	0.0507 (17)*	0.437 (14)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
P1	0.0236 (2)	0.0260 (2)	0.0267 (2)	0.00143 (15)	0.00188 (16)	0.00038 (16)
O1	0.0408 (7)	0.0355 (7)	0.0416 (8)	0.0016 (6)	−0.0139 (6)	−0.0054 (6)
O2	0.0250 (6)	0.0369 (7)	0.0388 (7)	−0.0022 (5)	0.0023 (5)	−0.0088 (5)
O3	0.0453 (8)	0.0385 (8)	0.0431 (8)	0.0168 (6)	0.0109 (6)	−0.0020 (6)
N1	0.0276 (7)	0.0276 (7)	0.0264 (7)	−0.0051 (5)	0.0022 (5)	−0.0039 (5)
C1	0.0364 (8)	0.0248 (8)	0.0339 (9)	0.0031 (7)	−0.0010 (7)	0.0004 (7)
C2	0.0282 (8)	0.0357 (9)	0.0319 (9)	0.0025 (7)	−0.0033 (7)	−0.0021 (7)
N2	0.0235 (7)	0.0417 (9)	0.0365 (8)	0.0052 (6)	0.0004 (6)	−0.0117 (7)
C3	0.0351 (9)	0.0280 (9)	0.0496 (11)	0.0007 (7)	−0.0025 (8)	−0.0020 (8)
C4	0.0293 (8)	0.0467 (11)	0.0357 (10)	−0.0037 (7)	0.0035 (7)	0.0015 (8)

Geometric parameters (Å, º)

P1—O3	1.5151 (13)	N2—C3	1.479 (2)
P1—O2	1.5230 (12)	N2—H8	0.9000
P1—O1	1.5234 (14)	N2—H9	0.9000
P1—H1	1.3200	C3—C4^ii	1.512 (3)
N1—C1	1.488 (2)	C3—H10	0.9700
N1—C2	1.492 (2)	C3—H11	0.9700
N1—H2	0.9000	C4—C3^ii	1.512 (3)
N1—H3	0.9000	C4—H12	0.9700
C1—C2^i	1.513 (2)	C4—H13	0.9700
C1—H4	0.9700	O4A—O4B	0.638 (5)
C1—H5	0.9700	O4A—H14	0.9549
C2—C1^i	1.513 (2)	O4A—H15	0.9296
C2—H6	0.9700	O4B—H14	0.9285
C2—H7	0.9700	O4B—H15	0.9594
N2—C4	1.477 (3)
O3—P1—O2	113.03 (8)	C4—N2—C3	111.13 (14)
O3—P1—O1	112.44 (8)	C4—N2—H8	109.4
O2—P1—O1	111.96 (8)	C3—N2—H8	109.4
O3—P1—H1	106.3	C4—N2—H9	109.4
O2—P1—H1	106.3	C3—N2—H9	109.4
O1—P1—H1	106.3	H8—N2—H9	108.0
C1—N1—C2	111.10 (13)	N2—C3—C4^ii	109.44 (15)
C1—N1—H2	109.4	N2—C3—H10	109.8
C2—N1—H2	109.4	C4^ii—C3—H10	109.8
C1—N1—H3	109.4	N2—C3—H11	109.8
C2—N1—H3	109.4	C4^ii—C3—H11	109.8
H2—N1—H3	108.0	H10—C3—H11	108.2
N1—C1—C2^i	110.40 (14)	N2—C4—C3^ii	110.48 (16)
N1—C1—H4	109.6	N2—C4—H12	109.6
C2^i—C1—H4	109.6	C3^ii—C4—H12	109.6
N1—C1—H5	109.6	N2—C4—H13	109.6
C2^i—C1—H5	109.6	C3^ii—C4—H13	109.6
H4—C1—H5	108.1	H12—C4—H13	108.1
N1—C2—C1^i	110.45 (14)	O4B—O4A—H14	68.0
N1—C2—H6	109.6	O4B—O4A—H15	72.8
C1^i—C2—H6	109.6	H14—O4A—H15	100.7
N1—C2—H7	109.6	O4A—O4B—H14	72.5
C1^i—C2—H7	109.6	O4A—O4B—H15	67.8
H6—C2—H7	108.1	H14—O4B—H15	100.5

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H2···O2^iii	0.90	1.84	2.7147 (19)	164
N1—H3···O2^iv	0.90	1.81	2.7043 (19)	172
N2—H8···O3^iv	0.90	1.77	2.642 (2)	163
N2—H9···O1^v	0.90	1.78	2.676 (2)	171
O4A—H14···O1	0.95	1.90	2.840 (4)	167
O4A—H15···O3^iv	0.93	1.90	2.811 (4)	168
O4B—H14···O1	0.93	1.90	2.752 (4)	151
O4B—H15···O3^iv	0.96	1.90	2.765 (4)	149
C1—H5···O4A^iii	0.97	2.38	3.300 (5)	159

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