Redetermination of piperazine di­hydro­chloride monohydrate

In the title compound, C₄H₁₂N₂²⁺·2Cl⁻·H₂O, the piperazinum dication has a center of symmetry, while the water mol­ecule is on the twofold axis. The structure exhibits chains of piperazinum dications linked together by N—H...Cl hydrogen bonds with chloride ions. Between the chains, there are weak hydrogen bonds of the O—H...Cl and C—H...Cl types.

Key indicators

• Single-crystal X-ray study
• T = 297 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.052
• wR factor = 0.149
• Data-to-parameter ratio = 28.5

checkCIF results

No syntax errors found



ADDSYM reports no extra symmetry


 Alert Level C:



REFLT_03
         From the CIF: _diffrn_reflns_theta_max           32.91
         From the CIF: _reflns_number_total               1453
         TEST2: Reflns within _diffrn_reflns_theta_max
         Count of symmetry unique reflns         1569
         Completeness (_total/calc)             92.61%
          Alert C: < 95% complete

PLAT_731  Alert C Bond    Calc     0.86(5), Rep     0.86(2) ....       2.50 s.u-Ratio
                     O1   -H1      1.555   1.555

PLAT_735  Alert C D-H     Calc     0.86(5), Rep     0.86(2) ....       2.50 s.u-Ratio
                     O1   -H1      1.555   1.555


 0 Alert Level A = Potentially serious problem

 0 Alert Level B = Potential problem

 3 Alert Level C = Please check

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S1. Comment

Hydrogen bonding plays an important role in the crystal engineering of organic solids (Desiraju, 1989; Melendez & Hamilton, 1998). There are many examples of one-, two- and three-dimentional objects formed by hydrogen bonds. The crystal structure of the title compound, (I), has already been reported by Rérat (1960), where a photographic method was used for the intensity measurement and an isotropic refinement of non-H atoms was applied. The refinement of low resultion (0.95 Å) and low quality of data resulted in a poor R value of 0.28 and no H atoms were located. We present here a redetermination of this structure using data from a Siemens SMART CCD diffractometer.

The atomic numbering for (I) is presented in Fig. 1. The structure exhibits hydrogen bonds of the type N—H···Cl, forming chains of hydrogen-bonded ions along the [110] and [110] directions (Fig. 2). The water molecules are on twofold axes and are located in the channels formed by crossed chains and they are invloved in weak hydrogen bonds of the O—H···Cl type with the nearest chains (Fig. 3). Thus, the water molecule shows high mobility which is reflected by high anisotropic displacement parameters of the O atom.

S2. Experimental

The title compound was prepared by the reaction of an ethanol solution of piperazine and HCl (37% in water) the the molar ratio 1:2.5 at room temperature. Crystals of (I) were obtained by slow evaporation of the solution.

S3. Refinement

The H atom of the water molecule was located from a difference Fourier map and were refined with a fixed isotropic displacement parameter and a restrained bond distance of 0.85 Å, whereas the other H atoms were constrained to idealized geometries using the approperiate ridding model.

Computing details

Data collection: SMART (Siemens, 1995); cell refinement: SAINT (Siemens, 1995); data reduction: SAINT and SADABS (Sheldrick, 1996); program(s) used to solve structure: SHELXTL (Bruker, 1997); program(s) used to refine structure: SHELXTL; molecular graphics: DIAMOND (Brandenburg, 2000).

Figures

	Fig. 1. The molecular structure of (I). Displacement ellipsoids are shown at the 50% probability level.
	Fig. 2. Representation of a hydrogen-bonded chain in the structure of (I). Each chain is involved in hydrogen bonding with water molecules.
	Fig. 3. A view along the c axis showing how chains are crossed with respect to each other. Water molecules are in the channels and are weakly bonded to the chains.

Piperazine dihydrochloride monohydrate

Crystal data

C4H12N2^2+·2Cl^−·H2O	F(000) = 376
Mr = 177.07	Dx = 1.408 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
a = 10.2233 (3) Å	Cell parameters from 1781 reflections
b = 6.3323 (3) Å	θ = 1–32°
c = 13.5389 (6) Å	µ = 0.71 mm^−1
β = 107.587 (2)°	T = 297 K
V = 835.50 (6) Å^3	Thin plate, colorless
Z = 4	0.40 × 0.20 × 0.04 mm

Data collection

Siemens SMART CCD diffractometer	1453 independent reflections
Radiation source: fine-focus sealed tube	974 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.043
Detector resolution: no pixels mm^-1	θmax = 32.9°, θmin = 3.2°
ω scans	h = −8→15
Absorption correction: multi-scan (Sheldrick, 1996)	k = −8→9
Tmin = 0.764, Tmax = 0.972	l = −20→20
3545 measured reflections

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)] = 0.052	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.149	H atoms treated by a mixture of independent and constrained refinement
S = 1.02	w = 1/[σ^2(Fo^2) + (0.0792P)^2] where P = (Fo^2 + 2Fc^2)/3
1453 reflections	(Δ/σ)max = 0.001
51 parameters	Δρmax = 0.48 e Å^−3
1 restraint	Δρmin = −0.35 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. Data were collected using a Siemens SMART CCD diffractometer at 297 K. A full sphere of reciprocal space was scanned by 0.3° steps in ω with a crystal–to–detector distance of 3.97 cm. Preliminary orientation matrices were obtained from the first 100 frames using SMART (Siemens, 1995). The collected frames were integrated using the preliminary orientation matrix which was updated every 100 frames·Final cell parameters were obtained by refinement on the position of 1781 reflections with I>10σ(I) after integration of all the frames data using SAINT (Siemens, 1995). The data were empirically corrected for absorption and other effects using SADABS (Sheldrick, 1996). 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
Cl1	0.79885 (6)	0.09493 (10)	0.66349 (4)	0.0422 (2)
N1	0.55069 (18)	0.4113 (3)	0.60246 (13)	0.0316 (4)
H1A	0.4929	0.4679	0.6338	0.040 (7)*
H1B	0.6105	0.3283	0.6486	0.055 (8)*
C1	0.4714 (2)	0.2815 (3)	0.51244 (16)	0.0348 (5)
H1C	0.4202	0.1738	0.5360	0.048 (7)*
H1D	0.5344	0.2112	0.4821	0.049 (8)*
O1	0.5000	0.0430 (6)	0.7500	0.0731 (9)
C2	0.6266 (2)	0.5831 (3)	0.56860 (17)	0.0346 (5)
H2A	0.6947	0.5223	0.5402	0.029 (6)*
H2B	0.6741	0.6695	0.6277	0.048 (7)*
H1	0.434 (4)	−0.035 (7)	0.757 (5)	0.150*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cl1	0.0371 (3)	0.0526 (4)	0.0370 (3)	0.0167 (2)	0.0113 (2)	0.0009 (2)
N1	0.0271 (8)	0.0362 (9)	0.0316 (8)	0.0039 (7)	0.0090 (6)	0.0020 (7)
C1	0.0365 (11)	0.0269 (10)	0.0425 (11)	−0.0020 (8)	0.0143 (9)	−0.0024 (8)
O1	0.055 (2)	0.0586 (19)	0.112 (3)	0.000	0.035 (2)	0.000
C2	0.0259 (10)	0.0397 (11)	0.0372 (10)	−0.0046 (8)	0.0078 (8)	−0.0061 (9)

Geometric parameters (Å, º)

N1—C2	1.487 (3)	C1—H1D	0.9700
N1—C1	1.491 (3)	O1—H1	0.86 (2)
N1—H1A	0.9000	C2—C1^i	1.510 (3)
N1—H1B	0.9000	C2—H2A	0.9700
C1—C2^i	1.510 (3)	C2—H2B	0.9700
C1—H1C	0.9700
C2—N1—C1	110.92 (16)	C2^i—C1—H1D	109.4
C2—N1—H1A	109.5	H1C—C1—H1D	108.0
C1—N1—H1A	109.5	N1—C2—C1^i	110.23 (17)
C2—N1—H1B	109.5	N1—C2—H2A	109.6
C1—N1—H1B	109.5	C1^i—C2—H2A	109.6
H1A—N1—H1B	108.0	N1—C2—H2B	109.6
N1—C1—C2^i	111.01 (17)	C1^i—C2—H2B	109.6
N1—C1—H1C	109.4	H2A—C2—H2B	108.1
C2^i—C1—H1C	109.4	H1—O1—H1^ii	109 (7)
N1—C1—H1D	109.4

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1B···Cl1	0.90	2.39	3.1412 (19)	141
N1—H1A···Cl1^iii	0.90	2.29	3.1541 (18)	162
O1—H1···Cl1^iv	0.86 (2)	2.82 (4)	3.492 (3)	137 (5)
C2—H2B···Cl1^v	0.97	2.80	3.475 (2)	128

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