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The asymmetric unit of the title compound, (C4H6N3O)2[SnCl6], contains one cytosinium cation and half a [SnCl6]2− anion, the anion lying on an inversion centre. The structure can be described as alternating layers of cytosinium and hexa­chloro­stannate ions along the c axis. The packing is stabilized by N—H...Cl and N—H...O hydrogen bonding, resulting in the formation of a two-dimensional network.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536805029727/dn6241sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S1600536805029727/dn6241Isup2.hkl
Contains datablock I

CCDC reference: 287548

Key indicators

  • Single-crystal X-ray study
  • T = 295 K
  • Mean [sigma](C-C) = 0.005 Å
  • R factor = 0.041
  • wR factor = 0.098
  • Data-to-parameter ratio = 23.9

checkCIF/PLATON results

No syntax errors found



Alert level C PLAT042_ALERT_1_C Calc. and Rep. MoietyFormula Strings Differ .... ? PLAT094_ALERT_2_C Ratio of Maximum / Minimum Residual Density .... 3.20 PLAT480_ALERT_4_C Long H...A H-Bond Reported H4B .. CL1 .. 2.92 Ang.
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 1 ALERT type 1 CIF construction/syntax error, inconsistent or missing data 1 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

Comment top

Studies of metal ion–nucleid acid interactions are of great current interest, since metal ions play a crucial role in the structure and function of nucleic acid and genetic information transfer (Salam & Aoki, 2000)·The antitumour activity of organotin(IV) complexes is also known (Kabanos et al., 1992).

Cytosine (6-aminopyrimidin-2-one) is one of the pyrimidines found in deoxyribonucleic acids. It has been the subject of several investigations with the aim of studying the electrostatic properties of its monohydrate form (Weber & Craven,1990), the relative stabilities of its tautomeric forms (Kobayashi, 1998) and its hydration effects and hydrogen bonding (Sivanesan et al., 2000). It offers many metal binding modes, namely via atom N3 (Tran Qui & Bagieu, 1990), through atom N4 (Muller et al., 1998), bridging through atoms N3 and N4 (Wienkotter et al., 1995), via atom O2 only (Cervantes et al., 1990), with chelation by atoms N3 and O2 (Aoki & Saenger, 1984), and bridging through atoms N3 and O2 (Lippert et al., 1984) via stronger N3 with additional weaker O2 interactions (Palaniandavar et al., 1996). Only one crystal structure based on Sn and cytosine has been reported to date (Casellato, 1995). Here, we present a new organic–inorganic hybrid compound, (I), based on Sn and cytosine, and examine the hydrogen bonding in the crystal structure.

The title structure, (I), consists of hexachlorostannate(IV) anions arranged around an inversion centre and two protonated cytosine rings (Fig. 1). The anionic sheet is parallel to the (001) plane and the distance between two sheets is c. The cytosine is monoprotonated at atom N3, as previously reported for the tetrachlorodimethylstannate and nitrate compounds (Casellato, 1995; Cherouana et al., 2003). The internal angle at N3 [C2—N3—C4 = 124.85 (10)°] is larger than the value of 119.4° reported in unprotonated cytosine (McClure & Craven, 1973). A similar effect has been observed in the structure of cytosinium dihydrogenmonophosphate (Bagieu-Beucher, 1990). There are two crystallographically equivalent (cytosinium) cations in (I), and these cations form layers parallel to the (011) plane.

The Sn atom is six-coordinated and forms a quasi-regular octahedral arrangement (Bouacida et al., 2005a). This [SnCl6]2− octahedron alternates with the cationic layers along the c axis (Fig. 2). The bond lengths are similar to those found in other octahedral SnIV compounds (Bouacida et al., 2005b).

The crystal packing in (I) is governed by classical hydrogen bonds (Fig.3). Atoms N1, N3, N4 and C5 of the cytosine participate in the formation of strong inter- and intramolecular (N—H···Cl and N—H···O) hydrogen bonds with hexachlorostannate and cytosine (Table 1), resulting in the formation of a two-dimensionnal network.

Experimental top

The title compound was crystallized by slow evaporation of an aqueous solution of cytosine, tin(II) chloride and hydrochloric acid in a molar ratio of 10:5:1. White prismatic crystals of (I) were obtained after two weeks and were manually separated for single-crystal X-ray analysis.

Refinement top

All H atoms were located in difference Fourier maps but were introduced in calculated positions and treated as riding on their parent atoms, with C—H = 0.93 Å and N—H = 0.86 Å, and with Uiso(H) = 1.2Ueq(C,N). [Please check added text] The very large residual electronic density (3.066 e Å−3) observed in the structure has no chemical significance and might be regarded as spurious.

Computing details top

Data collection: KappaCCD Server Software (Nonius, 1998); cell refinement: DENZO and SCALEPAK (Otwinowski & Minor, 1997); data reduction: DENZO and SCALEPAK; program(s) used to solve structure: SIR2002 (Burla et al., 2003); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia, 1997), PLUTON (Spek, 1990) and ATOMS for Windows (Dowty, 1995); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures top
[Figure 1] Fig. 1. A view of the title compound, with the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level. [Symmetry code: (i) 1 − x, 1 − y, 1 − z.]
[Figure 2] Fig. 2. A diagram of the layered packing and octahedra in the title compound, viewed down the a axis.
[Figure 3] Fig. 3. A view of the ionic stacking, showing the hydrogen bonds as dashed lines. H atoms not involved in hydrogen bonding have been omitted for clarity.
Bis(cytosinium) hexachlorostannate(IV) top
Crystal data top
(C4H6N3O)2[SnCl6]Z = 1
Mr = 555.63F(000) = 270
Triclinic, P1Dx = 2.100 Mg m3
Hall symbol: -P 1Mo Kα radiation, λ = 0.71073 Å
a = 6.910 (5) ÅCell parameters from 2533 reflections
b = 7.090 (5) Åθ = 2.3–30.1°
c = 9.270 (5) ŵ = 2.38 mm1
α = 101.86 (5)°T = 295 K
β = 98.36 (5)°Prism, white
γ = 90.51 (5)°0.1 × 0.1 × 0.1 mm
V = 439.4 (5) Å3
Data collection top
Nonius KappaCCD area-detector
diffractometer
2531 independent reflections
Radiation source: fine-focus sealed tube2279 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.052
ϕ scans, and ω scans with κ offsetsθmax = 30.1°, θmin = 2.3°
Absorption correction: multi-scan
(SORTAV; Blessing 1995)
h = 99
Tmin = 0.717, Tmax = 0.792k = 99
2533 measured reflectionsl = 134
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.041Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.098H-atom parameters constrained
S = 1.08 w = 1/[σ2(Fo2) + (0.02P)2]
where P = (Fo2 + 2Fc2)/3
2531 reflections(Δ/σ)max = 0.001
106 parametersΔρmax = 3.07 e Å3
0 restraintsΔρmin = 0.96 e Å3
Crystal data top
(C4H6N3O)2[SnCl6]γ = 90.51 (5)°
Mr = 555.63V = 439.4 (5) Å3
Triclinic, P1Z = 1
a = 6.910 (5) ÅMo Kα radiation
b = 7.090 (5) ŵ = 2.38 mm1
c = 9.270 (5) ÅT = 295 K
α = 101.86 (5)°0.1 × 0.1 × 0.1 mm
β = 98.36 (5)°
Data collection top
Nonius KappaCCD area-detector
diffractometer
2531 independent reflections
Absorption correction: multi-scan
(SORTAV; Blessing 1995)
2279 reflections with I > 2σ(I)
Tmin = 0.717, Tmax = 0.792Rint = 0.052
2533 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0410 restraints
wR(F2) = 0.098H-atom parameters constrained
S = 1.08Δρmax = 3.07 e Å3
2531 reflectionsΔρmin = 0.96 e Å3
106 parameters
Special details top

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 (Å2) top
xyzUiso*/Ueq
Sn0.50000.50000.50000.02302 (11)
Cl10.33727 (13)0.80139 (12)0.56055 (10)0.0371 (2)
Cl20.31063 (12)0.43568 (13)0.25047 (8)0.03329 (19)
Cl30.24638 (14)0.33496 (14)0.58581 (11)0.0418 (2)
O20.6402 (4)0.8662 (4)0.1099 (3)0.0415 (6)
N30.3457 (4)0.9160 (4)0.1916 (3)0.0284 (6)
H30.40180.98860.27330.034*
N10.3670 (4)0.7133 (4)0.0345 (3)0.0327 (6)
H10.43420.65170.09880.039*
N40.0499 (4)0.9823 (5)0.2735 (3)0.0355 (7)
H4A0.11021.05720.35260.043*
H4B0.07540.96700.26110.043*
C20.4639 (5)0.8323 (5)0.0894 (4)0.0294 (6)
C50.0574 (5)0.7710 (5)0.0384 (4)0.0312 (7)
H50.07780.74990.01990.037*
C60.1699 (5)0.6871 (5)0.0612 (4)0.0332 (7)
H60.11100.60950.15050.040*
C40.1488 (4)0.8921 (5)0.1723 (4)0.0257 (6)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Sn0.02457 (16)0.02343 (16)0.01863 (15)0.00029 (10)0.00150 (10)0.00006 (10)
Cl10.0354 (4)0.0300 (4)0.0389 (4)0.0084 (3)0.0021 (3)0.0039 (3)
Cl20.0318 (4)0.0417 (5)0.0211 (4)0.0020 (3)0.0033 (3)0.0006 (3)
Cl30.0411 (5)0.0451 (5)0.0404 (5)0.0110 (4)0.0122 (4)0.0081 (4)
O20.0225 (11)0.0607 (18)0.0384 (14)0.0024 (11)0.0050 (10)0.0035 (13)
N30.0231 (12)0.0325 (14)0.0258 (13)0.0025 (10)0.0007 (10)0.0004 (11)
N10.0297 (14)0.0367 (15)0.0292 (14)0.0029 (12)0.0069 (11)0.0009 (12)
N40.0273 (14)0.0453 (17)0.0311 (15)0.0001 (12)0.0056 (11)0.0009 (13)
C20.0252 (14)0.0349 (16)0.0286 (15)0.0020 (12)0.0051 (12)0.0069 (13)
C50.0232 (14)0.0337 (17)0.0329 (17)0.0008 (12)0.0001 (12)0.0009 (13)
C60.0304 (16)0.0366 (18)0.0274 (16)0.0020 (13)0.0013 (13)0.0014 (13)
C40.0222 (14)0.0282 (15)0.0270 (14)0.0005 (11)0.0029 (11)0.0071 (12)
Geometric parameters (Å, º) top
Sn—Cl32.4134 (17)N1—C61.353 (4)
Sn—Cl3i2.4134 (17)N1—C21.359 (4)
Sn—Cl12.4246 (18)N1—H10.8600
Sn—Cl1i2.4246 (18)N4—C41.305 (4)
Sn—Cl2i2.4385 (18)N4—H4A0.8600
Sn—Cl22.4385 (18)N4—H4B0.8600
O2—C21.219 (4)C5—C61.342 (5)
N3—C41.351 (4)C5—C41.414 (5)
N3—C21.385 (4)C5—H50.9300
N3—H30.8600C6—H60.9300
Cl3—Sn—Cl3i180.00 (4)C6—N1—C2123.1 (3)
Cl3—Sn—Cl190.03 (6)C6—N1—H1118.5
Cl3i—Sn—Cl189.97 (6)C2—N1—H1118.5
Cl3—Sn—Cl1i89.97 (6)C4—N4—H4A120.0
Cl3i—Sn—Cl1i90.03 (6)C4—N4—H4B120.0
Cl1—Sn—Cl1i180.0H4A—N4—H4B120.0
Cl3—Sn—Cl2i90.45 (6)O2—C2—N1123.5 (3)
Cl3i—Sn—Cl2i89.55 (6)O2—C2—N3121.9 (3)
Cl1—Sn—Cl2i90.15 (6)N1—C2—N3114.6 (3)
Cl1i—Sn—Cl2i89.85 (6)C6—C5—C4118.6 (3)
Cl3—Sn—Cl289.55 (6)C6—C5—H5120.7
Cl3i—Sn—Cl290.45 (6)C4—C5—H5120.7
Cl1—Sn—Cl289.85 (6)C5—C6—N1121.4 (3)
Cl1i—Sn—Cl290.15 (6)C5—C6—H6119.3
Cl2i—Sn—Cl2180.0N1—C6—H6119.3
C4—N3—C2124.8 (3)N4—C4—N3120.1 (3)
C4—N3—H3117.6N4—C4—C5122.5 (3)
C2—N3—H3117.6N3—C4—C5117.4 (3)
Symmetry code: (i) x+1, y+1, z+1.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N3—H3···Cl1ii0.862.463.265 (4)157
N1—H1···Cl2iii0.862.423.249 (4)162
N4—H4A···Cl3iv0.862.663.507 (4)169
N4—H4B···O2v0.862.263.032 (5)150
N4—H4B···Cl1vi0.862.923.490 (4)126
Symmetry codes: (ii) x+1, y+2, z+1; (iii) x+1, y+1, z; (iv) x, y+1, z; (v) x1, y, z; (vi) x, y+2, z+1.

Experimental details

Crystal data
Chemical formula(C4H6N3O)2[SnCl6]
Mr555.63
Crystal system, space groupTriclinic, P1
Temperature (K)295
a, b, c (Å)6.910 (5), 7.090 (5), 9.270 (5)
α, β, γ (°)101.86 (5), 98.36 (5), 90.51 (5)
V3)439.4 (5)
Z1
Radiation typeMo Kα
µ (mm1)2.38
Crystal size (mm)0.1 × 0.1 × 0.1
Data collection
DiffractometerNonius KappaCCD area-detector
diffractometer
Absorption correctionMulti-scan
(SORTAV; Blessing 1995)
Tmin, Tmax0.717, 0.792
No. of measured, independent and
observed [I > 2σ(I)] reflections
2533, 2531, 2279
Rint0.052
(sin θ/λ)max1)0.705
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.041, 0.098, 1.08
No. of reflections2531
No. of parameters106
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)3.07, 0.96

Computer programs: KappaCCD Server Software (Nonius, 1998), DENZO and SCALEPAK (Otwinowski & Minor, 1997), DENZO and SCALEPAK, SIR2002 (Burla et al., 2003), SHELXL97 (Sheldrick, 1997), ORTEP-3 (Farrugia, 1997), PLUTON (Spek, 1990) and ATOMS for Windows (Dowty, 1995), WinGX (Farrugia, 1999).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N3—H3···Cl1i0.862.463.265 (4)157
N1—H1···Cl2ii0.862.423.249 (4)162
N4—H4A···Cl3iii0.862.663.507 (4)169
N4—H4B···O2iv0.862.263.032 (5)150
N4—H4B···Cl1v0.862.923.490 (4)126
Symmetry codes: (i) x+1, y+2, z+1; (ii) x+1, y+1, z; (iii) x, y+1, z; (iv) x1, y, z; (v) x, y+2, z+1.
 

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