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The title salt, [Zn(C2N2H8)3]2[CdI4]I2, conventionally abbreviated [Zn(en)3]2[CdI4]I2, where en is ethyl­enediamine, contains discrete [Zn(en)3]2+ cations and [CdI4]2− anions with distorted octa­hedral and nearly tetra­hedral geometries, respectively, as well as uncoordinated I ions. The cation and the free I anion lie on twofold rotation axes and the [CdI4]2− anion lies on a \overline{4} axis in the space group I\overline{4}2d. The structure exhibits numerous weak inter-ionic hydrogen bonds of two types, viz. N—H...I(free ion) and N—H...I([CdI4]2−), which support the resulting three-dimensional framework.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270106017720/gd3008sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270106017720/gd3008Isup2.hkl
Contains datablock I

CCDC reference: 616106

Comment top

It has been shown that the preparation of complexes from zero-valent metals or metal oxides is a fascinating and promising means to the production of heterometallic compounds of unusual stoichiometry and structure (Pryma et al., 2003; Nesterova et al., 2005). The reaction of zinc oxide with cadmium iodide and ammonium iodide in a dimethylformamide solution of ethylenediamine (en) in the open air, using a molar ratio of ZnO:CdI2:NH4I:en of 2:1:4:6, gives colourless crystals of the title compound, [Zn(en)3]2[CdI4]I2, (I).

Single-crystal structural analysis confirms that (I) is an ionic compound and is built of discrete octahedral [Zn(en)3]2+ cations and tetrahedral [CdI4]2− and I anions, forming a three-dimensional framework by means of weak hydrogen bonds. The Cd atom lies on a 4 axis, while the cation and the free I ion both lie on twofold rotation axes. In the selected asymmetric unit (Fig. 1), the cation has a Δ configuration.

The ZnII atom in [Zn(en)3]2+ is coordinated by six N atoms from three bidentate en ligands, with Zn—N distances ranging from 2.171 (8) to 2.229 (8) Å (Table 1). The coordination environment of the complex cation is distorted octahedral, as can be seen from the trans N—Zn—N angles, which vary from 166.9 (4) to 169.3 (3)°, and the cis N—Zn—N angles, which vary from 79.7 (4) to 95.1 (3)°. The observed bond distances and angles are in accordance with those found for the similar zinc(II) complexes [Zn(en)3][Ni(C4N2S2)2], [Zn(en)3][Te3](0.5en) and [Zn(en)3](NO3)2 (Fu et al., 2004; Shreeve-Keyer et al., 1997; Neill et al., 1997). The CdII coordination environment has approximate tetrahedral symmetry. The [Mean?] Cd—I bond length in the [CdI4]2− anion is approximately equal to the sum of the covalent radii for the atoms of Cd (1.51 Å) and I (1.33 Å) (Batsanov, 1991) and is typical of its type (Bailey & Pennington, 1995; Nieuwenhuyzen et al., 1992; Kallel et al., 1981).

A complex system of hydrogen bonds links the ions of (I) into a three-dimensional framework. Each I anion is hydrogen bonded to three different [Zn(en)3]2+ units (Fig. 2), while each [CdI4]2− unit is hydrogen bonded to four different [Zn(en)3]2+ cations (Fig. 3). The non-coordinated atom I2 takes part in hydrogen bonding with the NH2 groups of en in the cations, being four-coordinated by H(N) atoms (Table 2). All four I atoms in the [CdI4]2− anion are two-coordinated by H(N) atoms, forming eight hydrogen bonds to [Zn(en)3]2+ cations. The hydrogen bonds interlink the [Zn(en)3]2+ and [CdI4]2− building blocks and I anions into a three-dimensional framework. The nearest I1···I2vii distance is 4.695 (5) Å [symmetry code: (vii) −y, x, −z], indicating no specific interaction between I atoms.

The title salt represents a suitable system for a comparison of the strengths of two types of N—H···I hydrogen bonds. Thus, the bonds involving the free I anions are ca 0.11 Å shorter than those involving the I atoms in the [CdI4]2− anion. Moreover, the mean value of all hydrogen bonds observed in [Zn(en)3]2[CdI4]I2 (3.81 Å), compared with the mean value found in [Cd(en)3]2[CdI4]I2 (3.76 Å) (Wieczorrek & Tebbe, 1998), indicates donor properties for the NH2 group somewhat stronger in [Cd(en)3]2+ than in [Zn(en)3]2+.

Experimental top

Zinc oxide (0.2 g, 0.0025 mol), CdI2 (0.455 g, 0.00125 mol), NH4I (0.72 g, 0.005 mol), dimethylformamide (20 ml) and ethylenediamine (0.5 ml, 0.0075 mol) were heated to 323–333 K and stirred magnetically for about 50 min. The solution was filtered and propan-2-ol (10 ml) was added to the resulting colourless solution. Colourless crystals of (I) suitable for single-crystal X-ray diffraction separated over one day; these were washed with dry propan-2-ol and dried in vacuo at room temperature (yield 1.32 g, 78%). An additional amount of product can be obtained from the filtrate. Analysis, calculated for C12H48CdZn2N12I6 (Mr = 1365.19): C 10.6, H 3.5, Cd 8.2, I 55.8, N 12.3, Zn 9.6%; found: C 10.6, H 3.7, Cd 8.3, I 55.4, N 12.5, Zn 9.6%.

Refinement top

All H atoms were located in difference maps and then treated as riding atoms, with C—H = 0.97 Å and N—H = 0.90 Å, and with Uiso(H) = 1.2Ueq(C,N). The absolute axis assignment (Jones, 1986) was established by means of the Flack parameter (Flack, 1983).

Computing details top

Data collection: P3 (Siemens, 1989); cell refinement: P3; data reduction: XDISK (Siemens, 1991); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XP (Siemens, 1991); software used to prepare material for publication: SHELXL97.

Figures top
[Figure 1] Fig. 1. The main structural units in the structure of (I), showing 40% probability displacement ellipsoids and the atom-numbering scheme. H atoms have been omitted for clarity.
[Figure 2] Fig. 2. A view of the environment of the I anion, based on hydrogen bonds. [Symmetry codes: (i) x, −1 − y, −z; (iv) −1 − x, y, −z; (v) −1/2 − x, y, −1/4 − z; (vi) −1 − x, −1/2 − y, −1/4 + z.]
[Figure 3] Fig. 3. A view of the [CdI4]2− environment, stabilized by hydrogen bonds. [Symmetry codes: (ii) −x, y, −z; (iii) −x, −y, z; (vii) x, −y, −z.]
bis[tris(ethylenediamine)zinc] tetraiodocadmate diiodide top
Crystal data top
[Zn(C2H8N2)3][CdI4]I2Dx = 2.435 Mg m3
Mr = 1365.16Mo Kα radiation, λ = 0.71073 Å
Tetragonal, I42dCell parameters from 24 reflections
Hall symbol: I -4 2bwθ = 10–14°
a = 14.803 (2) ŵ = 6.84 mm1
c = 16.991 (4) ÅT = 294 K
V = 3723.2 (11) Å3Block, colourless
Z = 40.4 × 0.2 × 0.2 mm
F(000) = 2520
Data collection top
Siemens P3/PC
diffractometer
825 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.034
Graphite monochromatorθmax = 25.1°, θmin = 1.8°
θ/2θ scansh = 017
Absorption correction: ψ scan
(North et al., 1968)
k = 017
Tmin = 0.127, Tmax = 0.255l = 020
3556 measured reflections2 standard reflections every 95 reflections
916 independent reflections intensity decay: 5%
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.027H-atom parameters constrained
wR(F2) = 0.062 w = 1/[σ2(Fo2) + (0.0332P)2 + 14.3589P]
where P = (Fo2 + 2Fc2)/3
S = 1.07(Δ/σ)max < 0.001
916 reflectionsΔρmax = 0.51 e Å3
76 parametersΔρmin = 0.62 e Å3
0 restraintsAbsolute structure: Flack (1983), with how many Friedel pairs
Primary atom site location: structure-invariant direct methodsAbsolute structure parameter: 0.07 (7)
Crystal data top
[Zn(C2H8N2)3][CdI4]I2Z = 4
Mr = 1365.16Mo Kα radiation
Tetragonal, I42dµ = 6.84 mm1
a = 14.803 (2) ÅT = 294 K
c = 16.991 (4) Å0.4 × 0.2 × 0.2 mm
V = 3723.2 (11) Å3
Data collection top
Siemens P3/PC
diffractometer
825 reflections with I > 2σ(I)
Absorption correction: ψ scan
(North et al., 1968)
Rint = 0.034
Tmin = 0.127, Tmax = 0.2552 standard reflections every 95 reflections
3556 measured reflections intensity decay: 5%
916 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.027H-atom parameters constrained
wR(F2) = 0.062 w = 1/[σ2(Fo2) + (0.0332P)2 + 14.3589P]
where P = (Fo2 + 2Fc2)/3
S = 1.07Δρmax = 0.51 e Å3
916 reflectionsΔρmin = 0.62 e Å3
76 parametersAbsolute structure: Flack (1983), with how many Friedel pairs
0 restraintsAbsolute structure parameter: 0.07 (7)
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
Cd10.00000.00000.00000.0372 (3)
I10.13938 (4)0.06598 (5)0.09476 (4)0.04409 (19)
Zn10.28000 (9)0.25000.12500.0302 (3)
N20.3762 (5)0.3284 (5)0.0570 (4)0.0388 (19)
H2C0.43130.30290.06000.047*
H2D0.35940.32950.00610.047*
N30.2971 (5)0.1311 (6)0.0459 (4)0.0417 (19)
H3C0.24790.09550.04790.050*
H3D0.30510.14930.00410.050*
N10.1666 (5)0.3072 (6)0.0593 (5)0.041 (2)
H1C0.17580.36660.05090.050*
H1D0.16150.27970.01230.050*
C20.3795 (8)0.4211 (7)0.0882 (7)0.056 (3)
H2A0.32860.45540.06850.068*
H2B0.43460.45050.07100.068*
I20.25000.39531 (6)0.12500.0500 (3)
C30.3767 (8)0.0817 (8)0.0736 (6)0.055 (3)
H3A0.43090.11070.05390.067*
H3B0.37520.02050.05320.067*
C10.0838 (6)0.2937 (7)0.1056 (6)0.043 (2)
H1A0.07900.34100.14490.051*
H1B0.03170.29800.07120.051*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Cd10.0359 (4)0.0359 (4)0.0398 (7)0.0000.0000.000
I10.0394 (3)0.0501 (4)0.0428 (3)0.0006 (3)0.0038 (3)0.0087 (3)
Zn10.0251 (7)0.0391 (8)0.0263 (6)0.0000.0000.0046 (6)
N20.032 (4)0.056 (5)0.028 (4)0.000 (4)0.004 (3)0.013 (4)
N30.042 (4)0.051 (5)0.032 (4)0.005 (4)0.007 (4)0.004 (4)
N10.033 (4)0.055 (5)0.036 (4)0.006 (4)0.012 (3)0.012 (4)
C20.046 (6)0.054 (7)0.069 (7)0.012 (5)0.003 (6)0.009 (6)
I20.0875 (8)0.0365 (5)0.0261 (4)0.0000.0032 (5)0.000
C30.054 (7)0.068 (8)0.044 (6)0.008 (6)0.002 (5)0.010 (5)
C10.034 (5)0.061 (6)0.033 (5)0.016 (4)0.003 (4)0.005 (5)
Geometric parameters (Å, º) top
Cd1—I12.7934 (9)N1—H1D0.9000
Zn1—N22.171 (8)C2—C3i1.499 (15)
Zn1—N12.186 (7)C2—H2A0.9700
Zn1—N32.229 (8)C2—H2B0.9700
N2—C21.472 (13)I2—I20.0000
N2—H2C0.9000C3—C2i1.499 (15)
N2—H2D0.9000C3—H3A0.9700
N3—C31.464 (13)C3—H3B0.9700
N3—H3C0.9000C1—C1i1.45 (2)
N3—H3D0.9000C1—H1A0.9700
N1—C11.470 (12)C1—H1B0.9700
N1—H1C0.9000
I1ii—Cd1—I1109.40 (2)Zn1—N3—H3C110.3
I1ii—Cd1—I1iii109.40 (2)C3—N3—H3D110.3
I1—Cd1—I1iii109.61 (3)Zn1—N3—H3D110.3
I1ii—Cd1—I1iv109.61 (3)H3C—N3—H3D108.6
I1—Cd1—I1iv109.40 (2)C1—N1—Zn1108.3 (5)
I1iii—Cd1—I1iv109.40 (2)C1—N1—H1C110.0
N2—Zn1—N2i98.0 (4)Zn1—N1—H1C110.0
N2—Zn1—N1i169.3 (3)C1—N1—H1D110.0
N2i—Zn1—N1i91.4 (3)Zn1—N1—H1D110.0
N2—Zn1—N191.4 (3)H1C—N1—H1D108.4
N2i—Zn1—N1169.3 (3)N2—C2—C3i109.6 (9)
N1i—Zn1—N179.7 (4)N2—C2—H2A109.8
N2—Zn1—N3i79.9 (3)C3i—C2—H2A109.8
N2i—Zn1—N3i91.5 (3)N2—C2—H2B109.8
N1i—Zn1—N3i94.9 (3)C3i—C2—H2B109.8
N1—Zn1—N3i95.1 (3)H2A—C2—H2B108.2
N2—Zn1—N391.5 (3)N3—C3—C2i110.9 (9)
N2i—Zn1—N379.9 (3)N3—C3—H3A109.5
N1i—Zn1—N395.1 (3)C2i—C3—H3A109.5
N1—Zn1—N394.9 (3)N3—C3—H3B109.5
N3i—Zn1—N3166.9 (4)C2i—C3—H3B109.5
C2—N2—Zn1109.2 (6)H3A—C3—H3B108.0
C2—N2—H2C109.8C1i—C1—N1111.4 (7)
Zn1—N2—H2C109.8C1i—C1—H1A109.4
C2—N2—H2D109.8N1—C1—H1A109.4
Zn1—N2—H2D109.8C1i—C1—H1B109.4
H2C—N2—H2D108.3N1—C1—H1B109.4
C3—N3—Zn1107.0 (6)H1A—C1—H1B108.0
C3—N3—H3C110.3
N2i—Zn1—N2—C2104.8 (7)N3i—Zn1—N3—C335.7 (15)
N1i—Zn1—N2—C246.6 (19)N2—Zn1—N1—C1160.9 (7)
N1—Zn1—N2—C280.3 (7)N2i—Zn1—N1—C147 (2)
N3i—Zn1—N2—C214.6 (6)N1i—Zn1—N1—C113.1 (5)
N3—Zn1—N2—C2175.2 (6)N3i—Zn1—N1—C181.0 (7)
N2—Zn1—N3—C384.1 (7)N3—Zn1—N1—C1107.4 (7)
N2i—Zn1—N3—C313.7 (7)Zn1—N2—C2—C3i40.7 (11)
N1i—Zn1—N3—C3104.2 (7)Zn1—N3—C3—C2i40.2 (11)
N1—Zn1—N3—C3175.7 (7)Zn1—N1—C1—C1i38.6 (11)
Symmetry codes: (i) x, y1/2, z+1/4; (ii) y, x, z; (iii) x, y, z; (iv) y, x, z.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N2—H2C···I2v0.902.903.758 (8)160
N2—H2D···I20.902.923.746 (7)153
N1—H1D···I1ii0.903.093.904 (9)150
N3—H3C···I1iii0.902.993.827 (8)156
Symmetry codes: (ii) y, x, z; (iii) x, y, z; (v) y1, x, z.

Experimental details

Crystal data
Chemical formula[Zn(C2H8N2)3][CdI4]I2
Mr1365.16
Crystal system, space groupTetragonal, I42d
Temperature (K)294
a, c (Å)14.803 (2), 16.991 (4)
V3)3723.2 (11)
Z4
Radiation typeMo Kα
µ (mm1)6.84
Crystal size (mm)0.4 × 0.2 × 0.2
Data collection
DiffractometerSiemens P3/PC
diffractometer
Absorption correctionψ scan
(North et al., 1968)
Tmin, Tmax0.127, 0.255
No. of measured, independent and
observed [I > 2σ(I)] reflections
3556, 916, 825
Rint0.034
(sin θ/λ)max1)0.596
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.027, 0.062, 1.07
No. of reflections916
No. of parameters76
H-atom treatmentH-atom parameters constrained
w = 1/[σ2(Fo2) + (0.0332P)2 + 14.3589P]
where P = (Fo2 + 2Fc2)/3
Δρmax, Δρmin (e Å3)0.51, 0.62
Absolute structureFlack (1983), with how many Friedel pairs
Absolute structure parameter0.07 (7)

Computer programs: P3 (Siemens, 1989), P3, XDISK (Siemens, 1991), SHELXS97 (Sheldrick, 1990), SHELXL97 (Sheldrick, 1997), XP (Siemens, 1991), SHELXL97.

Selected geometric parameters (Å, º) top
Cd1—I12.7934 (9)Zn1—N12.186 (7)
Zn1—N22.171 (8)Zn1—N32.229 (8)
I1i—Cd1—I1109.40 (2)N2—Zn1—N3iii79.9 (3)
I1—Cd1—I1ii109.61 (3)N1—Zn1—N3iii95.1 (3)
N2—Zn1—N2iii98.0 (4)N2—Zn1—N391.5 (3)
N2—Zn1—N1iii169.3 (3)N1—Zn1—N394.9 (3)
N2—Zn1—N191.4 (3)N3iii—Zn1—N3166.9 (4)
N1iii—Zn1—N179.7 (4)
Symmetry codes: (i) y, x, z; (ii) x, y, z; (iii) x, y1/2, z+1/4.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N2—H2C···I2iv0.902.903.758 (8)159.5
N2—H2D···I20.902.923.746 (7)153.1
N1—H1D···I1i0.903.093.904 (9)149.6
N3—H3C···I1ii0.902.993.827 (8)156.0
Symmetry codes: (i) y, x, z; (ii) x, y, z; (iv) y1, x, z.
 

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