Cadmium copper tetrachloride tetrahydrate

The double salt [CuCl₂(H₂O)₂{CdCl₂}]·2H₂O crystallizes in the triclinic rather than the monoclinic system as reported previously. The structure consists of sheets in the ac plane with slightly distorted octahedral CdCl₆ [Cd—Cl 2.5813 (8)–2.6943 (8) Å] connected by Cd—Cl—Cd bridges in the Cd equatorial plane along a, and by Cd—Cl—Cu bridges to layers of square-planar CuCl₂(H₂O)₂ along c. There are long axial Cu—Cl interactions of 2.8623 (7) Å and additional water of hydration is hydrogen bonded to coordinated water and chloride ligands. The additional water connects the ac sheets into a three-dimensional network. Both Cd and Cu occupy different sites. The Cu...Cu and Cd...Cd distances are 3.8274 (6) Å.

S1. Comment

The structural analysis of the title salt was performed in support of an examination of its magnetic behavior. A previous Weissenberg camera diffraction study using Cu radiation (Thrierr-Sorel et al., 1969) indicated a C-centered monoclinic cell. In contrast, we find the structure to be triclinic with a cell one-quarter the volume of that reported earlier. The green columnar crystals tend to twin and only parallelepiped-shaped crystals were indexed successfully.

The title structure (Fig. 1) consists of approximately octahedral CdCl₆ linked into a linear polymer by double Cl bridges running along a. The Cl—Cd—Cl angles are within 8° of 90 or 180°. The axial Cl ligand bridges to Cu, which forms square-planar CuCl₂(H₂O)₂, and these Cl bridges connect the Cd and Cu atoms into sheets in the ac plane (Fig. 2). Cl1 also forms a long interaction with a neighboring Cu atom with an axial Cu—Cl distance of 2.8623 (7) Å. Angles around copper are within 6° of 90 or 180°. The water coordinated to Cu is hydrogen bonded to non-coordinated lattice water, which is in turn hydrogen bonded to Cl2. These hydrogen bonds connect the sheets along the b direction to form a three-dimensional network. The Cu and Cd atoms occupy different 1 sites such that the closest Cd···Cd and Cu···Cu distances are both one-unit translations along the a axis, i.e. 3.8274 (6) Å.

S2. Experimental

The CdCl₂–CuCl₂–H₂O system has been explored previously (Bassett & Strain, 1952). Crystals were obtained after about four weeks by evaporation from a solution containing CuCl₂^.2H₂O (18.75 g, 0.11 mol) and CdCl₂ (9.17 g, 0.05 mol) dissolved in H₂O (20 ml).

S3. Refinement

Crystal decay was monitored by recollection of the first 50 frames periodically throughout the data collection. H atoms were refined isotropically in observed positions.

Computing details

Data collection: SMART (Bruker, 1998); cell refinement: SMART; data reduction: SHELXTL (Sheldrick, 1997a); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997b); molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Figures

	Fig. 1. View of the title compound showing the numbering scheme and 50% probability ellipsoids.
	Fig. 2. Stereopacking diagram viewed along the a axis with c down and b to the left.

(I)

Crystal data

[CuCl2(H2O)2{CdCl2}]·2H2O	Z = 1
Mr = 389.80	F(000) = 185
Triclinic, P1	Dx = 2.801 Mg m^−3
a = 3.8274 (6) Å	Mo Kα radiation, λ = 0.71073 Å
b = 7.1591 (11) Å	Cell parameters from 2232 reflections
c = 8.7756 (13) Å	θ = 5.9–56.6°
α = 87.595 (2)°	µ = 5.72 mm^−1
β = 82.735 (2)°	T = 299 K
γ = 75.639 (2)°	Column, green
V = 231.06 (6) Å^3	0.38 × 0.10 × 0.05 mm

Data collection

CCD area-detector diffractometer	1094 independent reflections
Radiation source: normal-focus sealed tube	1033 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.028
ω scans	θmax = 28.3°, θmin = 2.3°
Absorption correction: multi-scan (Blessing, 1995)	h = −5→5
Tmin = 0.475, Tmax = 0.810	k = −9→9
2771 measured reflections	l = −11→11

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.027	All H-atom parameters refined
wR(F^2) = 0.071	w = 1/[σ^2(Fo^2) + (0.0468P)^2 + 0.0268P] where P = (Fo^2 + 2Fc^2)/3
S = 1.07	(Δ/σ)max < 0.001
1094 reflections	Δρmax = 0.65 e Å^−3
66 parameters	Δρmin = −0.84 e Å^−3
0 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.417 (14)

Special details

Experimental. Crystal decay was monitored by re-collection of the first fifty frames periodically throughout the data collection.

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
Cd	0	0	0.5000	0.02412 (17)
Cl2	0.38166 (18)	0.25311 (10)	0.47309 (8)	0.0263 (2)
Cl1	0.06418 (18)	−0.05094 (11)	0.19434 (8)	0.0288 (2)
Cu	0.5000	0	0	0.02544 (18)
O1	0.3722 (7)	0.2746 (3)	0.0369 (3)	0.0314 (5)
H1A	0.342 (11)	0.344 (6)	−0.044 (5)	0.043 (11)*
H1B	0.197 (14)	0.323 (8)	0.099 (6)	0.061 (15)*
O2	0.2219 (9)	0.5051 (4)	−0.2125 (4)	0.0374 (6)
H2B	0.196 (19)	0.446 (11)	−0.291 (9)	0.09 (2)*
H2A	0.372 (18)	0.556 (9)	−0.233 (7)	0.065 (19)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cd	0.0220 (2)	0.0295 (2)	0.0218 (2)	−0.00814 (13)	−0.00270 (12)	0.00072 (12)
Cl2	0.0249 (3)	0.0253 (4)	0.0285 (4)	−0.0069 (3)	−0.0018 (3)	0.0016 (3)
Cl1	0.0270 (4)	0.0423 (4)	0.0178 (3)	−0.0111 (3)	−0.0003 (3)	−0.0001 (3)
Cu	0.0270 (3)	0.0238 (3)	0.0228 (3)	−0.0045 (2)	0.0040 (2)	−0.0003 (2)
O1	0.0373 (12)	0.0267 (12)	0.0273 (11)	−0.0045 (10)	0.0009 (10)	−0.0016 (9)
O2	0.0498 (16)	0.0310 (13)	0.0304 (12)	−0.0104 (12)	−0.0007 (10)	0.0015 (9)

Geometric parameters (Å, º)

Cd—Cl2^i	2.5813 (8)	Cu—O1	1.935 (2)
Cd—Cl2	2.5813 (8)	Cu—O1^v	1.935 (2)
Cd—Cl2^ii	2.6303 (7)	Cu—Cl1^v	2.3139 (7)
Cd—Cl2^iii	2.6303 (7)	Cu—Cl1^iv	2.8623 (7)
Cd—Cl1^i	2.6943 (8)	O1—H1A	0.85 (5)
Cd—Cl1	2.6943 (8)	O1—H1B	0.82 (5)
Cl2—Cd^iv	2.6303 (7)	O2—H2B	0.85 (8)
Cl1—Cu	2.3139 (7)	O2—H2A	0.75 (7)
Cl2^i—Cd—Cl2	180.00 (3)	Cl1^i—Cd—Cl1	180.0
Cl2^i—Cd—Cl2^ii	85.49 (3)	Cd—Cl2—Cd^iv	94.51 (3)
Cl2—Cd—Cl2^ii	94.51 (3)	Cu—Cl1—Cd	130.99 (3)
Cl2^i—Cd—Cl2^iii	94.51 (3)	Cu^iv—Cl1—Cd^iv	128.44 (3)
Cl2—Cd—Cl2^iii	85.49 (3)	O1—Cu—O1^v	180.0
Cl2^ii—Cd—Cl2^iii	180.00 (3)	O1—Cu—Cl1	92.00 (8)
Cl2^i—Cd—Cl1^i	93.24 (2)	O1^v—Cu—Cl1	88.00 (8)
Cl2—Cd—Cl1^i	86.76 (2)	O1—Cu—Cl1^v	88.00 (8)
Cl2^ii—Cd—Cl1^i	92.51 (2)	O1^v—Cu—Cl1^v	92.00 (8)
Cl2^iii—Cd—Cl1^i	87.49 (2)	Cl1—Cu—Cl1^v	180.00 (5)
Cl2^i—Cd—Cl1	86.76 (2)	Cu—O1—H1A	114 (3)
Cl2—Cd—Cl1	93.24 (2)	Cu—O1—H1B	120 (4)
Cl2^ii—Cd—Cl1	87.49 (2)	H1A—O1—H1B	105 (4)
Cl2^iii—Cd—Cl1	92.51 (2)	H2B—O2—H2A	109 (7)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1A···O2	0.85 (5)	1.87 (5)	2.718 (4)	174 (4)
O1—H1B···O2^vi	0.82 (5)	1.95 (5)	2.752 (4)	165 (5)
O2—H2A···O1^vii	0.76 (7)	2.57 (6)	3.050 (4)	124 (6)
O2—H2A···Cl2^vii	0.76 (7)	2.66 (7)	3.259 (3)	138 (6)
O2—H2B···Cl2^viii	0.85 (8)	2.46 (8)	3.269 (3)	158 (6)

Symmetry codes: (vi) −x, −y+1, −z; (vii) −x+1, −y+1, −z; (viii) x, y, z−1.