Dicyanidobis(thio­urea-κS)cadmium(II) monohydrate

In the title compound, [Cd(CN)₂(CH₄N₂S)₂]·H₂O, the Cd atom lies on a twofold rotation axis and is bonded to two S atoms of thio­urea and two C atoms of the cyanide anions in a distorted tetra­hedral environment. The crystal structure is stabilized by N—H...N(CN), N—H...O, O—H...N and N—H...S hydrogen bonds.

Key indicators

• Single-crystal X-ray study
• T = 294 K
• Mean [sigma](N-C) = 0.003 Å
• R factor = 0.018
• wR factor = 0.043
• Data-to-parameter ratio = 16.6

checkCIF/PLATON results

No syntax errors found



Alert level B
PLAT232_ALERT_2_B Hirshfeld Test Diff (M-X)  Cd1    --  S1      ..      50.94 su

Alert level C
PLAT232_ALERT_2_C Hirshfeld Test Diff (M-X)  Cd1    --  C1      ..       7.98 su
PLAT250_ALERT_2_C Large U3/U1 Ratio for Average U(i,j) Tensor ....       2.17
PLAT352_ALERT_3_C Short   N-H Bond (0.87A)   N3     -   H5     ...       0.73 Ang.

Alert level G
PLAT128_ALERT_4_G Alternate Setting of Space-group P2/c    .......      P2/n

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

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   3 ALERT type 2 Indicator that the structure model may be wrong or deficient
   1 ALERT type 3 Indicator that the structure quality may be low
   1 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

---

S1. Comment

The interest in cadmium(II) complexes of thiourea (Tu) arises because some of them exhibit non-linear optical properties (Rajesh et al., 2004) and they are useful for the convenient preparation of cadmium sulfide based semiconducting materials by their thermal decomposition in air (Stoev et al., 1994). Several crystallographic reports about cadmium(II) complexes of thiourea reveal that it coordinates to cadmium(II) via the sulfur atom (Corao et al., 1969; Marcos et al., 1998; Wang et al., 2002). Recently, we have reported the crystal structures of cadmium(II) complexes of N,N'-dimethylthiourea (Dmtu), [Cd(Dmtu)₂Cl₂] (Malik et al., 2010) and tetramethylthiourea (Tmtu), [Cd(Tmtu)₂Br₂] (Nawaz et al., 2010a) and [Cd(Tmtu)₂I₂] (Nawaz et al., 2010b). Herein, we report the crystal structure of a cadmium cyanide complex of thiourea, biscyanidobis(thiourea-kS)cadmium(II) monohydrate, [Cd(Tu)₂(CN)₂].H₂O. The present investigation was carried out in view of our continuous interest in the structural chemistry of cyanido complexes of d¹⁰ metal ions with thiourea type ligands (Ahmad et al., 2009; Hanif et al., 2007).

In the title compound, the Cd atom is situated on a twofold axis of symmetry and is bonded to two cyanide carbon atoms and two sulfur atoms of thiourea (Figure 1). The four coordinate metal ion adopts a severely distorted tetrahedral geometry, the bond angles being in the range of 95.76 (4) - 143.5 (1) °. The Cd—S and Cd—C bond lengths are 2.6363 (5) Å and 2.211 (2) Å respectively. These are in agreement with those reported for related compounds (Marcos et al., 1998; Malik et al. 2010; Nawaz et al., 2010a,b; Wang et al., 2002; Yoshikawa et al., 2003). The two C—N bond lengths in thiourea, C2—N2 and C2—N3, are 1.312 (2) Å and 1.305 (2) Å respectively. The CNH₂ fragments of the two thiourea molecules are essentially planar, the maximum deviation from the mean plane being for the nitrogen atoms with 0.03 (1) Å. These values are consistent with a significant CN double bond character and electron delocalization in the SCN₂ moiety. To the best of our knowledge, this is the first X-ray structure of a cadmium complex having both sulfur containing ligands and cyanide in its coordination sphere.

The molecules pack to form columns parallel to the b direction (Figure 2). Within these columns, each metal ion interacts with two sulfur atoms of a neighboring molecule (Cd···S: 3.3140 (5) Å), hence extending the tetra-coordinate inner-sphere to a hexa-coordinate outer-sphere with a distorted octahedral environment. These interactions confer to the molecular columns a polymeric chain character.

Intermolecular hydrogen bonding takes place through N—H···S as well as N—H···N(CN) interactions (Table 1). The complex molecules also interact with the water molecules through C—N···H—O and N—H···O bonds. In this scheme the water molecule is tetrahedrally hydrogen bonded to four complex molecules. This generates a three-dimensional hydrogen bonding network where the molecular chains are interconnected through hydrogen bonding either directly or through the water molecules.

Related literature

For background to cadmium(II) complexes of thiourea-type ligands, see: Corao et al. (1969); Malik et al. (2010); Marcos et al. (1998); Nawaz et al. (2010a,b); Wang et al. (2002). For the non-linear optical properties and semi-conducting applications of Cd–thiourea complexes, see: Rajesh et al. (2004); Stoev et al. (1994). For the structures of cyanido complexes, see: Ahmad et al. (2009); Hanif et al. (2007); Yoshikawa et al. (2003).

S2. Experimental

To 0.17 g (1.0 mmol) cadmium(II) cyanide (prepared by the reaction of CdCl₂.H₂O and KCN in 1:2 molar ratio in water) suspended in 15 mL water was added 2 equivalents of thiourea in methanol. Yellow precipitates formed, were filtered and the filtrate was kept for crystallization. Crystals were grown by slow evaporation of a water/methanol solution at room temperature.

S3. Refinement

All non-H atoms were refined anisotropically. Hydrogen atoms were located in a difference Fourier map and freely refined isotropically.

Computing details

Data collection: SMART (Bruker, 2008); cell refinement: SAINT (Bruker, 2008); data reduction: SAINT (Bruker, 2008); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures

	Fig. 1. The molecular structure of the title compound with the atomic numbering scheme. Displacement ellipsoids are drawn at the 30% probability level (Symmetry code: i = 0.5-x, y, 0.5-z).
	Fig. 2. Packing diagram of the title complex showing the H-bonding interactions.

Dicyanidobis(thiourea-κS)cadmium(II) monohydrate

Crystal data

[Cd(CN)2(CH4N2S)2]·H2O	F(000) = 328
Mr = 334.70	Dx = 1.940 Mg m^−3
Monoclinic, P2/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yac	Cell parameters from 7211 reflections
a = 10.5955 (6) Å	θ = 2.3–28.3°
b = 4.0782 (3) Å	µ = 2.25 mm^−1
c = 13.4127 (8) Å	T = 294 K
β = 98.738 (1)°	Parallelepiped, yellow
V = 572.84 (6) Å^3	0.29 × 0.28 × 0.24 mm
Z = 2

Data collection

Bruker SMART APEX area-detector diffractometer	1430 independent reflections
Radiation source: normal-focus sealed tube	1376 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.017
ω scans	θmax = 28.3°, θmin = 2.3°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −14→14
Tmin = 0.561, Tmax = 0.614	k = −5→5
7211 measured reflections	l = −17→17

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)] = 0.018	All H-atom parameters refined
wR(F^2) = 0.043	w = 1/[σ^2(Fo^2) + (0.0181P)^2 + 0.3434P] where P = (Fo^2 + 2Fc^2)/3
S = 1.10	(Δ/σ)max < 0.001
1430 reflections	Δρmax = 0.73 e Å^−3
86 parameters	Δρmin = −0.74 e Å^−3
0 restraints	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.072 (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
Cd1	0.2500	−0.06581 (5)	0.2500	0.03756 (9)
S1	0.35766 (4)	0.31297 (11)	0.39821 (3)	0.03220 (11)
C1	0.06927 (16)	−0.2357 (5)	0.29604 (12)	0.0340 (3)
C2	0.28176 (16)	0.2070 (4)	0.49904 (12)	0.0322 (3)
N1	−0.02293 (17)	−0.3264 (6)	0.31974 (14)	0.0499 (4)
N2	0.16014 (18)	0.2695 (6)	0.49815 (14)	0.0535 (5)
N3	0.3466 (2)	0.0687 (6)	0.57851 (14)	0.0518 (5)
O1	0.7500	0.2524 (6)	0.2500	0.0451 (5)
H1	0.811 (3)	0.376 (7)	0.267 (2)	0.059 (8)*
H2	0.121 (3)	0.355 (8)	0.451 (2)	0.068 (9)*
H3	0.127 (3)	0.243 (7)	0.551 (2)	0.056 (7)*
H4	0.429 (4)	0.021 (8)	0.578 (3)	0.078 (10)*
H5	0.313 (3)	0.013 (7)	0.619 (3)	0.064 (9)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cd1	0.02792 (11)	0.05064 (14)	0.03652 (12)	0.000	0.01265 (7)	0.000
S1	0.0315 (2)	0.0395 (2)	0.02651 (18)	−0.00063 (16)	0.00713 (14)	0.00102 (16)
C1	0.0321 (8)	0.0416 (9)	0.0291 (7)	0.0028 (7)	0.0072 (6)	0.0029 (7)
C2	0.0352 (8)	0.0371 (8)	0.0249 (7)	−0.0004 (7)	0.0063 (6)	−0.0031 (6)
N1	0.0367 (8)	0.0677 (12)	0.0477 (9)	−0.0040 (8)	0.0145 (7)	0.0077 (9)
N2	0.0403 (9)	0.0892 (16)	0.0338 (8)	0.0155 (10)	0.0148 (7)	0.0124 (9)
N3	0.0417 (9)	0.0832 (15)	0.0319 (8)	0.0100 (9)	0.0099 (7)	0.0164 (9)
O1	0.0373 (10)	0.0563 (13)	0.0423 (10)	0.000	0.0076 (8)	0.000

Geometric parameters (Å, º)

Cd1—C1^i	2.2108 (17)	C2—N2	1.312 (2)
Cd1—C1	2.2108 (17)	N2—H2	0.78 (3)
Cd1—S1	2.6363 (5)	N2—H3	0.84 (3)
Cd1—S1^i	2.6363 (5)	N3—H4	0.90 (4)
S1—C2	1.7300 (17)	N3—H5	0.72 (4)
C1—N1	1.134 (2)	O1—H1	0.83 (3)
C2—N3	1.305 (2)
C1^i—Cd1—C1	143.47 (10)	N3—C2—S1	119.80 (15)
C1^i—Cd1—S1	95.76 (4)	N2—C2—S1	121.13 (14)
C1—Cd1—S1	105.48 (5)	C2—N2—H2	120 (2)
C1^i—Cd1—S1^i	105.48 (5)	C2—N2—H3	120.4 (19)
C1—Cd1—S1^i	95.76 (4)	H2—N2—H3	119 (3)
S1—Cd1—S1^i	108.26 (2)	C2—N3—H4	119 (2)
C2—S1—Cd1	104.11 (6)	C2—N3—H5	119 (3)
N1—C1—Cd1	179.22 (18)	H4—N3—H5	122 (3)
N3—C2—N2	119.05 (18)

Symmetry code: (i) −x+1/2, y, −z+1/2.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N3—H5···O1^ii	0.72 (4)	2.26 (4)	2.961 (2)	166 (3)
N3—H4···S1^ii	0.90 (4)	2.61 (4)	3.470 (2)	159 (3)
N2—H3···N1^iii	0.84 (3)	2.22 (3)	3.035 (2)	163 (3)
N2—H2···N1^iv	0.78 (3)	2.51 (3)	3.286 (3)	171 (3)
O1—H1···N1^v	0.83 (3)	2.16 (3)	2.988 (2)	176 (3)

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