Poly[di­aqua­tetra-μ-seleno­cyanato-cadmium(II)dipotassium(I)]

In the title compound, [CdK₂(NCSe)₄(H₂O)₂]_n, the cadmium(II) cation is situated on a twofold rotation axis and is coordinated in a slightly distorted tetra­hedral geometry by two symmetry-related μ-1,1,1,3 and two-symmetry related μ-1,1,3,3 bridging seleno­cyanate anions, all of which are Se bonded. These bridging seleno­cyanate anions are further coordinated to two symmetry-related potassium ions. Each of the potassium ions is coordinated by one terminally bonded water mol­ecule and six seleno­cyanate anions, two of which are crystallographically independent. The asymmetric unit consists of one cadmium and one potassium cation, two bridging seleno­cyanate anions and one water mol­ecule. The polymeric subunits are further connected via the seleno­cyanate anions into a three-dimensional coordination network. In this coordination network, intramolecular hydrogen bonds between neighbouring water molecules can be found.

Related literature

For general background to transition metal thio- and seleno­cyanates and N-donor ligands, see: Näther et al. (2007); Bhosekar et al. (2006); Wriedt & Näther (2010); Wriedt et al. (2010a,b). For related structures, see: Shi et al. (2007); Couhorn & Dronskowski (2004). For similar coordination modes in azido anions, see: El Fallah et al. (2008); Guo & Mak (1998).

Experimental

Crystal data

• [CdK₂(NCSe)₄(H₂O)₂]

• M_r = 646.55

• Monoclinic, C 2/c

• a = 21.574 (3) Å

• b = 4.4055 (4) Å

• c = 17.9316 (19) Å

• β = 112.454 (13)°

• V = 1575.1 (3) ų

• Z = 4

• Mo Kα radiation

• μ = 11.15 mm⁻¹

• T = 170 K

• 0.05 × 0.04 × 0.03 mm

Data collection

• Stoe IPDS-1 diffractometer

• Absorption correction: numerical (X-SHAPE and X-RED32; Stoe & Cie, 2008) T_min = 0.588, T_max = 0.713

• 4687 measured reflections

• 1800 independent reflections

• 1355 reflections with I > 2σ(I)

• R_int = 0.057

Refinement

• R[F² > 2σ(F²)] = 0.037

• wR(F²) = 0.090

• S = 1.00

• 1800 reflections

• 79 parameters

• H-atom parameters constrained

• Δρ_max = 0.90 e Å⁻³

• Δρ_min = −0.94 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1—H2⋯O1^i	0.85	1.92	2.760 (6)	167
Symmetry code: (i) .

Data collection: X-AREA (Stoe & Cie, 2008); cell refinement: X-AREA; data reduction: X-AREA; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: XP in SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXL97.

Supporting information

S1. Comment

In our ongoing investigations on the synthesis, structures and properties of transition metal thio- and selenocyanates and N-donor ligands (Näther, Bhosekar & Jess (2007); Bhosekar et al. (2006); Wriedt & Näther (2010); Wriedt, Jess & Näther (2010a,b)) we have reacted cadmium(II) dinitrate with potassium selenocyanate and pyrimidine in water in order to prepare cadmium selenocyanato coordination polymers with pyrimidine as co-ligand. In this reaction single crystals were obtained, which were identified as the title compound by single-crystal X-ray diffraction.

In the title compound of composition [CdK₂(NCSe)₄(H₂O)₂]_n (Fig. 1) the cadmium cation is located on a twofold rotation axis and is coordinated to ten potassium cations via two µ-1,1,1,3 bridging and two µ-1,1,3,3 bridging selenocyanato anions. The cadmium cation is coordinated by Se atoms of four selenocyanato anions in a slightly distorted tetrahedral geometry. The Cd—Se distances range between 2.655 (7) Å and 2.672 (8) Å and the Se—Cd—Se angles range between 106.68 (21)° and 116.96 (17)° (Tab. 1). The potassium cations are each heptacoordinated by three N-atoms of three µ-1,1,1,3 bridging selenocyanato anions, two N-atoms of two µ-1,1,3,3 bridging selenocyanato anions, one Se-atom of one µ-1,1,3,3 bridging selenocyanato anion and one terminally bonded water molecule within an irregular geometry. The K—N distances range between 2.805 (69) Å and 3.083 (71) Å, the K—O distance amounts to 2.763 (45) Å and the K—Se distance is 3.694 (16) Å. The angles around the K atoms range between 63.10 (2)° and 155.51 (19)° (Tab. 1). The large K—Se and K—K distances are not unusual and similar values can be found in related structures (Shi et al., 2007; Couhorn & Dronskowski, 2004). The Cd and K atoms are connected by the bridging selenocyanato anions into a three-dimensional coordination network (Fig. 2). It must be noted that the present bridging modes of the selenocyanato anions are observed for the first time in a coordination polymer and similar coordination modes can be found for azido anions (El Fallah et al., 2008; Guo & Mak, 1998).

Related literature

For general background to transition metal thio- and selenocyanates and N-donor ligands, see: Näther et al. (2007); Bhosekar et al. (2006); Wriedt & Näther (2010); Wriedt et al. (2010a,b). For related structures, see: Shi et al. (2007); Couhorn & Dronskowski (2004). For similar coordination modes in azido anions, see: El Fallah et al. (2008); Guo & Mak (1998).

S2. Experimental

Cd(NO₃)₂ x 4H₂O was obtained from Merck, KNCSe and pyrimidine were obtained from Alfa Aesar. 1 mmol (174 mg) Cd(NO₃)₂ x 4H₂O, 2 mmol (288 mg) KNCSe, 4 mmol (320 mg) pyrimidine and 3 ml acetonitrile were reacted in a closed snap-cap vial without stirring. After the mixture had been standing for several days in the dark at room temperature colourless block shaped single crystals of the title compound were obtained.

S3. Refinement

The O—H hydrogen atoms were located in difference map, set to idealized distances and refined isotropic using a riding model with U_eq(H) = 1.5*U_eq(O).

Computing details

Data collection: X-AREA (Stoe & Cie, 2008); cell refinement: X-AREA (Stoe & Cie, 2008); data reduction: X-AREA (Stoe & Cie, 2008); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: XP in SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures

	Fig. 1. : Crystal structure of the title compound with labelling and displacement ellipsoids drawn at the 50% probability level. Symmetry codes: i: x, y + 1, z; ii: -x + 1/2, -y + 3/2, -z + 1; iii: -x + 1, -y + 1, -z + 1; iv: -x + 1, -y + 2, -z + 1; v: -x + 1, y, -z + 3/2; vi: x, y - 1, z.
	Fig. 2. : Crystal structure of the title compound with view along the crystallographic b-axis.

Poly[diaquatetra-µ-selenocyanato-cadmium(II)dipotassium(I)]

Crystal data

[CdK2(NCSe)4(H2O)2]	F(000) = 1176
Mr = 646.55	Dx = 2.726 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 4533 reflections
a = 21.574 (3) Å	θ = 2.5–27.5°
b = 4.4055 (4) Å	µ = 11.15 mm^−1
c = 17.9316 (19) Å	T = 170 K
β = 112.454 (13)°	Block, colourless
V = 1575.1 (3) Å^3	0.05 × 0.04 × 0.03 mm
Z = 4

Data collection

Stoe IPDS-1 diffractometer	1800 independent reflections
Radiation source: fine-focus sealed tube	1355 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.057
ϕ Scans scans	θmax = 27.5°, θmin = 2.5°
Absorption correction: numerical (X-SHAPE and X-RED32; Stoe & Cie, 2008)	h = −28→26
Tmin = 0.588, Tmax = 0.713	k = −5→4
4687 measured reflections	l = −23→23

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)] = 0.037	H-atom parameters constrained
wR(F^2) = 0.090	w = 1/[σ^2(Fo^2) + (0.052P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 1.00	(Δ/σ)max = 0.001
1800 reflections	Δρmax = 0.90 e Å^−3
79 parameters	Δρmin = −0.94 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: 0.00083 (16)

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	0.5000	0.53865 (16)	0.7500	0.02159 (19)
Se1	0.39046 (3)	0.19271 (15)	0.71167 (3)	0.02260 (18)
C1	0.3440 (3)	0.3582 (16)	0.6125 (4)	0.0257 (13)
N1	0.3131 (3)	0.4620 (16)	0.5497 (3)	0.0320 (13)
Se2	0.49070 (3)	0.85366 (16)	0.61994 (3)	0.02357 (19)
C2	0.5606 (4)	0.6741 (17)	0.6015 (4)	0.0293 (15)
N2	0.6047 (4)	0.5706 (16)	0.5900 (4)	0.0381 (15)
K1	0.32739 (8)	0.9210 (4)	0.44900 (8)	0.0291 (3)
O1	0.2416 (3)	0.8171 (13)	0.2915 (3)	0.0375 (12)
H1	0.1999	0.8495	0.2786	0.056*
H2	0.2463	0.6824	0.2602	0.056*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cd1	0.0190 (3)	0.0260 (4)	0.0195 (3)	0.000	0.0071 (2)	0.000
Se1	0.0206 (3)	0.0229 (3)	0.0237 (3)	−0.0014 (2)	0.0078 (2)	0.0018 (2)
C1	0.022 (3)	0.026 (4)	0.033 (3)	−0.006 (3)	0.015 (3)	−0.004 (3)
N1	0.028 (3)	0.037 (4)	0.028 (3)	−0.003 (3)	0.007 (2)	0.002 (3)
Se2	0.0244 (3)	0.0258 (4)	0.0208 (3)	0.0022 (3)	0.0089 (2)	0.0020 (2)
C2	0.038 (4)	0.029 (4)	0.022 (3)	−0.004 (3)	0.013 (3)	−0.002 (3)
N2	0.047 (4)	0.033 (4)	0.048 (3)	0.008 (3)	0.033 (3)	0.002 (3)
K1	0.0348 (8)	0.0263 (8)	0.0292 (7)	0.0001 (6)	0.0155 (6)	−0.0005 (6)
O1	0.032 (3)	0.042 (3)	0.039 (3)	−0.007 (3)	0.015 (2)	−0.008 (2)

Geometric parameters (Å, º)

Cd1—Se2	2.6548 (7)	Se2—C2	1.841 (7)
Cd1—Se1	2.6720 (8)	C2—N2	1.143 (10)
Se1—C1	1.827 (7)	N2—K1^iii	2.847 (7)
C1—N1	1.161 (9)	N2—K1^iv	2.904 (7)
N1—K1	2.806 (6)	K1—O1	2.760 (5)
N1—K1^i	3.076 (7)	O1—H1	0.8501
N1—K1^ii	3.083 (7)	O1—H2	0.8500
Se2—Cd1—Se2^v	116.97 (4)	N1^vi—K1—N1^ii	63.1 (2)
Se2—Cd1—Se1	108.03 (2)	O1—K1—Se2	152.89 (13)
Se2^v—Cd1—Se1	106.66 (2)	N1—K1—Se2	73.29 (13)
Se2—Cd1—Se1^v	106.66 (2)	N2^iii—K1—Se2	74.08 (15)
Se2^v—Cd1—Se1^v	108.03 (2)	N2^iv—K1—Se2	81.55 (15)
Se1—Cd1—Se1^v	110.45 (4)	N1^vi—K1—Se2	81.53 (12)
C1—Se1—Cd1	97.2 (2)	N1^ii—K1—Se2	129.50 (11)
N1—C1—Se1	178.5 (6)	O1—K1—K1^vi	99.55 (13)
C1—N1—K1	138.2 (5)	N1—K1—K1^vi	136.11 (14)
C1—N1—K1^i	96.6 (5)	N2^iii—K1—K1^vi	139.52 (14)
K1—N1—K1^i	96.89 (17)	N2^iv—K1—K1^vi	39.54 (13)
C1—N1—K1^ii	105.1 (5)	N1^vi—K1—K1^vi	39.22 (12)
K1—N1—K1^ii	103.6 (2)	N1^ii—K1—K1^vi	80.38 (13)
K1^i—N1—K1^ii	116.9 (2)	Se2—K1—K1^vi	94.61 (3)
C2—Se2—Cd1	98.1 (2)	O1—K1—K1^i	80.45 (13)
C2—Se2—K1	118.2 (2)	N1—K1—K1^i	43.89 (14)
Cd1—Se2—K1	119.93 (3)	N2^iii—K1—K1^i	40.48 (14)
N2—C2—Se2	178.1 (7)	N2^iv—K1—K1^i	140.46 (13)
C2—N2—K1^iii	152.8 (6)	N1^vi—K1—K1^i	140.78 (12)
C2—N2—K1^iv	105.5 (6)	N1^ii—K1—K1^i	99.62 (13)
K1^iii—N2—K1^iv	99.98 (19)	Se2—K1—K1^i	85.39 (3)
O1—K1—N1	110.08 (18)	K1^vi—K1—K1^i	180.00 (9)
O1—K1—N2^iii	80.18 (19)	O1—K1—K1^ii	92.68 (12)
N1—K1—N2^iii	78.66 (19)	N1—K1—K1^ii	40.35 (13)
O1—K1—N2^iv	94.85 (19)	N2^iii—K1—K1^ii	111.46 (15)
N1—K1—N2^iv	154.22 (19)	N2^iv—K1—K1^ii	148.48 (14)
N2^iii—K1—N2^iv	99.98 (19)	N1^vi—K1—K1^ii	76.76 (12)
O1—K1—N1^vi	123.42 (18)	N1^ii—K1—K1^ii	36.10 (12)
N1—K1—N1^vi	96.89 (17)	Se2—K1—K1^ii	104.44 (5)
N2^iii—K1—N1^vi	155.49 (19)	K1^vi—K1—K1^ii	108.99 (4)
N2^iv—K1—N1^vi	73.55 (17)	K1^i—K1—K1^ii	71.01 (4)
O1—K1—N1^ii	75.99 (16)	K1—O1—H1	118.5
N1—K1—N1^ii	76.4 (2)	K1—O1—H2	126.1
N2^iii—K1—N1^ii	136.7 (2)	H1—O1—H2	108.6
N2^iv—K1—N1^ii	117.42 (19)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H2···O1^vii	0.85	1.92	2.760 (6)	167

Symmetry code: (vii) −x+1/2, y−1/2, −z+1/2.