Piperazinium(2+) hexa­aqua­iron(II) bis(sulfate)

In the crystal structure of the title compound, (C₄H₁₂N₂)[Fe(H₂O)₆](SO₄)₂, hydrogen bonds link the piperazinium cation, the hexa­aquairon(II) cation and the sulfate anions into a three-dimensional network. The [Fe(H₂O)₆]²⁺ and piperazinium cations each lie on a centre of symmetry.

Key indicators

• Single-crystal X-ray study
• T = 273 K
• Mean [sigma](C-C) = 0.004 Å
• R factor = 0.033
• wR factor = 0.085
• Data-to-parameter ratio = 11.4

checkCIF/PLATON results

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Alert level C
PLAT164_ALERT_4_C Nr. of Refined C-H H-Atoms in Heavy-At Struct...          4
PLAT242_ALERT_2_C Check Low       Ueq as Compared to Neighbors for        Fe1
PLAT242_ALERT_2_C Check Low       Ueq as Compared to Neighbors for         S1

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

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   2 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

This report describes a study on the reactions of iron(II) sulfate and piperazine under solvothermal conditions. We have previously described a 4,4-bipyridine salt of hexaquairon(II) sulfate, accompanied by two uncoordinated water molecules (Fu et al., 2005). A similar reaction with N,N-diethylformamide (DMF) as solvent and piperazine as diamine yielded the title compound, (I) (Fig. 1), although DMF was not incorporated into the crystal structure. The compound can be regarded as a double salt of piperazinium sulfate and hexaquairon(II) sulfate.

The [Fe(H₂O)₆]²⁺ and C₄H₁₂N₂²⁺ cations and the sulfate anions interact through hydrogen bonds (Table 2), forming a three-dimensional network. The organic cation and the Fe atom each lie on an inversion center. There are only four examples in the literature of a hexaaquametal sulfate salt having an organic piperazine cation. The structures of piperazinium hexaquacobalt(II) disulfate (Pan et al., 2003) and piperazinium hexaquanickel(II) disulfate (Meng et al., 2004) are similar to that of the title compound, but hemi(piperazinium) hexaquaaluminium(III) bis(sulfate) tetrahydrate (Bataille, 2003) and piperazinium hexaquazinc(II) bis(sulfate) (Rekik et al., 2005) have additional hydrogen-bond interactions with uncoordinated water molecules.

S2. Experimental

Iron(II) sulfate heptahydrate (0.278 g, 1 mmol) was dissolved in DMF (7 ml) under constant stirring. A drop of concentrated sulfuric acid (0.06 ml, 1 mmol) was added, followed by piperazine (0.086 g, 1 mmol). The final mixture was placed in a 15 ml Teflon-lined Parr bomb, which was heated at 383 K for 2 d. The bomb was cooled and opened to reveal pale-green block-shaped crystals in about 40% yield with respect to Fe.

S3. Refinement

H atoms were located in difference Fourier maps and were refined with distance restraints of O—H = N—H = 0.85 (1) Å and C—H =0.95 (1) Å; their displacement parameters were refined freely.

Computing details

Data collection: SMART (Bruker, 2002); cell refinement: SMART; data reduction: SAINT (Bruker, 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPII (Johnson, 1976); software used to prepare material for publication: SHELX97.

Figures

Fig. 1. ORTEPII plot (Johnson, 1976) of (I), showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probablility level.

Piperazinium(2+) hexaaquairon(II) bis(sulfate)

Crystal data

(C4H12N2)[Fe(H2O)6](SO4)2	F(000) = 464
Mr = 444.22	Dx = 1.809 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 25 reflections
a = 7.8345 (6) Å	θ = 2.8–27.0°
b = 9.3814 (8) Å	µ = 1.25 mm^−1
c = 11.0965 (9) Å	T = 273 K
β = 91.284 (1)°	Block, pale green
V = 815.37 (11) Å^3	0.18 × 0.15 × 0.14 mm
Z = 2

Data collection

Bruker SMART CCD area-detector diffractometer	1763 independent reflections
Radiation source: fine-focus sealed tube	1679 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.021
ϕ and ω scans	θmax = 27.0°, θmin = 2.8°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −8→10
Tmin = 0.806, Tmax = 0.844	k = −10→11
4636 measured reflections	l = −10→14

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)] = 0.033	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.085	w = 1/[σ^2(Fo^2) + (0.0439P)^2 + 0.5012P] where P = (Fo^2 + 2Fc^2)/3
S = 1.10	(Δ/σ)max < 0.001
1763 reflections	Δρmax = 0.63 e Å^−3
155 parameters	Δρmin = −0.36 e Å^−3
0 restraints	Extinction correction: SHELXL, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.026 (2)

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
Fe1	0.0000	0.5000	0.5000	0.02379 (16)
S1	0.52503 (6)	0.45971 (6)	0.77949 (5)	0.02620 (17)
O1	0.1949 (2)	0.36551 (19)	0.43356 (17)	0.0362 (4)
O2	0.1901 (2)	0.6046 (2)	0.60118 (19)	0.0436 (5)
O3	0.0411 (3)	0.6370 (2)	0.35063 (17)	0.0417 (4)
O4	0.3852 (2)	0.35897 (18)	0.79981 (17)	0.0406 (4)
O5	0.5180 (2)	0.5102 (2)	0.65443 (16)	0.0423 (5)
O6	0.6905 (2)	0.3888 (2)	0.80446 (17)	0.0466 (5)
C2	0.0810 (3)	0.5914 (3)	0.9133 (2)	0.0354 (5)
O7	0.5067 (3)	0.5777 (2)	0.86399 (19)	0.0534 (5)
N1	0.1743 (3)	0.4728 (3)	0.9743 (2)	0.0375 (5)
C1	−0.0584 (3)	0.6459 (3)	0.9928 (3)	0.0404 (6)
H9	0.157 (4)	0.664 (3)	0.898 (3)	0.046 (8)*
H3	0.174 (4)	0.674 (4)	0.642 (3)	0.050 (9)*
H5	0.023 (4)	0.721 (4)	0.352 (3)	0.047 (9)*
H7	−0.121 (4)	0.717 (4)	0.953 (3)	0.056 (9)*
H2	0.177 (4)	0.293 (4)	0.386 (3)	0.060 (10)*
H1	0.281 (5)	0.397 (4)	0.408 (3)	0.057 (10)*
H4	0.274 (4)	0.578 (3)	0.620 (3)	0.042 (9)*
H11	0.250 (5)	0.433 (4)	0.926 (3)	0.074 (11)*
H8	−0.016 (4)	0.686 (3)	1.073 (3)	0.049 (8)*
H6	0.134 (5)	0.631 (4)	0.312 (3)	0.067 (11)*
H10	0.037 (4)	0.562 (3)	0.836 (3)	0.050 (8)*
H12	0.233 (5)	0.506 (4)	1.037 (4)	0.067 (11)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Fe1	0.0207 (2)	0.0218 (2)	0.0290 (3)	0.00017 (14)	0.00509 (16)	−0.00031 (15)
S1	0.0224 (3)	0.0259 (3)	0.0305 (3)	−0.00013 (18)	0.0054 (2)	0.00480 (19)
O1	0.0287 (8)	0.0283 (9)	0.0521 (10)	−0.0005 (6)	0.0132 (7)	−0.0076 (7)
O2	0.0307 (9)	0.0352 (10)	0.0646 (13)	0.0045 (7)	−0.0107 (9)	−0.0148 (9)
O3	0.0477 (11)	0.0303 (10)	0.0479 (10)	0.0083 (8)	0.0201 (8)	0.0085 (8)
O4	0.0352 (9)	0.0344 (9)	0.0526 (10)	−0.0091 (7)	0.0107 (7)	0.0029 (8)
O5	0.0275 (8)	0.0641 (13)	0.0353 (9)	−0.0002 (7)	0.0034 (7)	0.0169 (8)
O6	0.0293 (9)	0.0603 (12)	0.0505 (11)	0.0129 (8)	0.0087 (7)	0.0195 (9)
C2	0.0324 (11)	0.0418 (13)	0.0325 (12)	−0.0044 (10)	0.0080 (9)	0.0028 (10)
O7	0.0713 (13)	0.0325 (10)	0.0569 (12)	−0.0076 (9)	0.0159 (10)	−0.0056 (8)
N1	0.0223 (9)	0.0501 (13)	0.0406 (12)	0.0029 (8)	0.0095 (9)	0.0005 (9)
C1	0.0385 (13)	0.0330 (13)	0.0502 (15)	0.0059 (10)	0.0107 (11)	0.0019 (11)

Geometric parameters (Å, º)

Fe1—O2	2.0894 (18)	O2—H4	0.73 (3)
Fe1—O2^i	2.0894 (18)	O3—H5	0.80 (3)
Fe1—O1	2.1253 (16)	O3—H6	0.86 (4)
Fe1—O1^i	2.1253 (16)	C2—N1	1.486 (3)
Fe1—O3^i	2.1273 (18)	C2—C1	1.509 (3)
Fe1—O3	2.1273 (18)	C2—H9	0.92 (3)
S1—O7	1.460 (2)	C2—H10	0.96 (3)
S1—O5	1.4663 (18)	N1—C1^ii	1.487 (3)
S1—O4	1.4678 (16)	N1—H11	0.89 (4)
S1—O6	1.4781 (17)	N1—H12	0.88 (5)
O1—H2	0.87 (4)	C1—N1^ii	1.487 (3)
O1—H1	0.79 (4)	C1—H7	0.93 (3)
O2—H3	0.80 (4)	C1—H8	1.01 (3)
O2—Fe1—O2^i	180.0	Fe1—O2—H3	124 (2)
O2—Fe1—O1	87.49 (8)	Fe1—O2—H4	128 (3)
O2^i—Fe1—O1	92.51 (8)	H3—O2—H4	106 (3)
O2—Fe1—O1^i	92.51 (8)	Fe1—O3—H5	123 (2)
O2^i—Fe1—O1^i	87.49 (8)	Fe1—O3—H6	120 (2)
O1—Fe1—O1^i	180.00 (9)	H5—O3—H6	103 (3)
O2—Fe1—O3^i	89.05 (8)	N1—C2—C1	110.0 (2)
O2^i—Fe1—O3^i	90.95 (8)	N1—C2—H9	108.8 (18)
O1—Fe1—O3^i	91.96 (7)	C1—C2—H9	109.3 (18)
O1^i—Fe1—O3^i	88.04 (7)	N1—C2—H10	110.8 (19)
O2—Fe1—O3	90.95 (8)	C1—C2—H10	111.7 (18)
O2^i—Fe1—O3	89.05 (8)	H9—C2—H10	106 (3)
O1—Fe1—O3	88.04 (7)	C2—N1—C1^ii	112.0 (2)
O1^i—Fe1—O3	91.96 (7)	C2—N1—H11	111 (3)
O3^i—Fe1—O3	180.0	C1^ii—N1—H11	105 (3)
O7—S1—O5	111.14 (12)	C2—N1—H12	110 (2)
O7—S1—O4	107.77 (11)	C1^ii—N1—H12	112 (2)
O5—S1—O4	109.95 (11)	H11—N1—H12	106 (3)
O7—S1—O6	108.62 (13)	N1^ii—C1—C2	110.1 (2)
O5—S1—O6	109.70 (10)	N1^ii—C1—H7	110 (2)
O4—S1—O6	109.63 (11)	C2—C1—H7	110.4 (19)
Fe1—O1—H2	124 (2)	N1^ii—C1—H8	104.5 (17)
Fe1—O1—H1	121 (2)	C2—C1—H8	114.3 (17)
H2—O1—H1	102 (3)	H7—C1—H8	108 (3)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H12···O7^iii	0.88 (5)	2.43 (4)	3.080 (3)	131 (3)
N1—H12···O6^iii	0.88 (5)	2.10 (5)	2.953 (3)	165 (3)
O3—H6···O6^iv	0.86 (4)	1.91 (4)	2.757 (2)	167 (3)
N1—H11···O7	0.89 (4)	2.54 (4)	3.065 (3)	119 (3)
O2—H4···O5	0.73 (3)	2.04 (3)	2.768 (3)	174 (3)
O1—H1···O5^iv	0.79 (4)	1.94 (4)	2.733 (2)	175 (3)
O1—H2···O6^v	0.87 (4)	1.94 (4)	2.783 (3)	164 (3)
O3—H5···O7^vi	0.80 (3)	1.90 (4)	2.695 (3)	173 (3)
O2—H3···O4^vii	0.80 (4)	1.91 (4)	2.698 (3)	165 (3)

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