catena-Poly[[iodidocadmium(II)]-di-μ-iodido-[iodidocadmium(II)]-bis­(μ-4-methyl­pyridine N-oxide)]

In the title complex, [CdI₂(C₆H₇NO)]_n, the Cd^II ion exhibits a trigonal–bipyramidal coordination geometry [Cd—O = 2.272 (4) Å and Cd—I = 2.7054 (7)–2.8049 (8) Å], with iodide anions and 4-methyl­pyridine N-oxide ligands acting as bridging groups to form a one-dimensional chain structure.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.009 Å
• R factor = 0.030
• wR factor = 0.070
• Data-to-parameter ratio = 21.0

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT029_ALERT_3_C _diffrn_measured_fraction_theta_full Low .......       0.98
PLAT062_ALERT_4_C Rescale T(min) & T(max) by .....................       0.95
PLAT154_ALERT_1_C The su's on the Cell Angles are Equal  (x 10000)        300 Deg.
PLAT342_ALERT_3_C Low Bond Precision on C-C Bonds (x 1000) Ang ...          9
PLAT764_ALERT_4_C Overcomplete CIF Bond List Detected (Rep/Expd) .       1.15 Ratio

Alert level G
PLAT199_ALERT_1_G Check the Reported _cell_measurement_temperature        293 K
PLAT200_ALERT_1_G Check the Reported _diffrn_ambient_temperature .        293 K
PLAT794_ALERT_5_G Check Predicted Bond Valency for Cd1         (2)       2.21

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

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

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S1. Comment

Complexes containing Cd(II) are very common and useful, and they have played an important role in functional materials, especially in the area of optics (Pecaut et al., 1993; Selvasekarapandian et al., 1997). In published work most Cd^II ions assume octahedron geometry with six coordinated atoms (Shi et al., 2006), and Cd(II) complexes with coordination number five are limited (Reger et al., 2002). We report here a novel one-dimensional Cd(II) complex (I) with five coordinated atoms.

The asymmetric unit and symmetry-related fragments of (I) are shown in Fig. 1. Atom Cd1 is in a distorted trigonal-bipyramidal CdO₂I₃ coordination geometry (Table 1). Atom I1 acts as a bridging ligand coordinated two Cd^II ions with a separation of 3.9511 (11) Å, which creates a four-membered ring with the four atoms strictly coplanar by virtue of the crystallographic inversion center which is in the middle of the four-membered ring. A neutral 4-methylpyridine N-oxide group also acts as bridging ligand with a pair of Cd^II ions having a separation of 3.8705 (11) Å also leading to the formation of a four-membered ring with the four atoms strictly coplanar by virtue of the crystallographic inversion center which is also at the middle of this four-membered ring. The dihedral angle of the two planes is 56.99 °. The two kinds of four-membered rings connect alternately, leading to the formation of a one-dimensional zigzag chain along the a axis as shown in Fig. 2. There is one weak interchain C—H···I interaction [H6A···I1(x, -1 + y, -1 + z) = 3.24 Å; C6—H6A···I1(x, -1 + y, -1 + z) = 160°. The chain structure in (I) is very similar to that of the complex {[Cd(µ-I)(µ-ONC₅H₅)]I}_n (where ONC₅H₅ is pyridine N-oxide) (Sawitzki & Schnering, 1974), but the crystal system and space groups of the two crystals are different and probably attributed to the minor difference of the methyl substitution.

Related literature

In most reported crystal structures the Cd^II ion has coordination number six (Shi et al., 2006), while those with coordination number five are rarer (Reger et al., 2002). The title structure is similar to that of {[Cd(µ-I)(µ-ONC₅H₅)]I}_n (where ONC₅H₅ is pyridine N-oxide) (Sawitzki & Schnering, 1974).

For related literature, see: Pecaut et al. (1993); Selvasekarapandian et al. (1997).

S2. Experimental

Cd(ClO₄)₂.6H₂O (0.2724 g, 0.649 mmol), 4-methylpyridine N-oxide (0.0793 g, 0.727 mmol) and NaI (0.2417 g, 1.61 mmol) were dissolved in 10 ml H₂O, respectively, and then the three solutions were mixed together. The colorless single crystals (I) were obtained after allowing the mixed solution to stand at room temperature for two weeks.

S3. Refinement

The H atoms were placed in calculated positions and refined as riding, with C—H = 0.93 Å, U_iso(H) = 1.2_eq(C) for pyridine ring; C—H = 0.96 Å, U_iso(H) = 1.5_eq(C) for the methyl group.

Computing details

Data collection: SMART (Bruker, 1997); cell refinement: SAINT (Bruker, 1997); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Bruker, 2001); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Figures

	Fig. 1. Part of the structure of (I) showing the atom numbering scheme with thermal ellipsoids drawn at the 30% probability level. [Symmetry codes: (i) -x, -y + 2, -z + 2; (ii) -x + 1, -y + 2, -z + 2].
	Fig. 2. Part of the crystal structure of (I). Dashed lines indicate weak C—H···I interactions.

catena-Poly[[iodidocadmium(II)]-di-µ-iodido-[iodidocadmium(II)]-bis(µ- 4-methylpyridine N-oxide)]

Crystal data

[CdI2(C6H7NO)]	Z = 2
Mr = 475.33	F(000) = 424
Triclinic, P1	Dx = 2.880 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 7.0584 (16) Å	Cell parameters from 1365 reflections
b = 8.4025 (19) Å	θ = 2.6–26.8°
c = 9.875 (2) Å	µ = 7.58 mm^−1
α = 102.633 (3)°	T = 293 K
β = 96.050 (3)°	Block, colorless
γ = 103.510 (3)°	0.09 × 0.08 × 0.07 mm
V = 548.1 (2) Å^3

Data collection

Bruker SMART APEX CCD diffractometer	2147 independent reflections
Radiation source: fine-focus sealed tube	1839 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.017
φ and ω scans	θmax = 26.2°, θmin = 2.1°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −8→8
Tmin = 0.549, Tmax = 0.619	k = −8→10
3046 measured reflections	l = −12→10

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)] = 0.030	H-atom parameters constrained
wR(F^2) = 0.070	w = 1/[σ^2(Fo^2) + (0.0308P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 1.02	(Δ/σ)max = 0.037
2147 reflections	Δρmax = 0.85 e Å^−3
102 parameters	Δρmin = −0.89 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: 0.0063 (5)

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	0.25296 (6)	0.96122 (5)	1.07178 (4)	0.03312 (14)
I1	0.12264 (5)	1.25617 (5)	1.10555 (4)	0.03973 (14)
I2	0.31135 (7)	0.81337 (6)	1.28439 (4)	0.05230 (16)
C6	0.1724 (11)	0.2298 (9)	0.5226 (7)	0.0588 (19)
H6A	0.1267	0.2389	0.4302	0.088*
H6B	0.0671	0.1605	0.5548	0.088*
H6C	0.2813	0.1795	0.5192	0.088*
N1	0.3549 (6)	0.7153 (6)	0.8070 (5)	0.0322 (10)
C4	0.2630 (9)	0.4203 (8)	0.7651 (6)	0.0419 (14)
H4	0.2387	0.3249	0.8005	0.050*
O1	0.4163 (6)	0.8687 (5)	0.8971 (4)	0.0409 (10)
C1	0.3308 (9)	0.7026 (8)	0.6688 (6)	0.0438 (14)
H1	0.3538	0.7997	0.6357	0.053*
C5	0.3229 (9)	0.5765 (8)	0.8557 (6)	0.0419 (14)
H5	0.3418	0.5869	0.9522	0.050*
C2	0.2719 (9)	0.5459 (9)	0.5757 (6)	0.0475 (16)
H2	0.2549	0.5384	0.4796	0.057*
C3	0.2378 (9)	0.4012 (8)	0.6209 (6)	0.0397 (14)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cd1	0.0310 (2)	0.0323 (2)	0.0372 (2)	0.01002 (18)	0.00636 (17)	0.00883 (17)
I1	0.0335 (2)	0.0305 (2)	0.0513 (3)	0.00987 (16)	−0.00021 (17)	0.00418 (17)
I2	0.0631 (3)	0.0504 (3)	0.0487 (3)	0.0166 (2)	0.0047 (2)	0.0239 (2)
C6	0.070 (5)	0.042 (4)	0.051 (4)	0.004 (4)	0.014 (4)	−0.005 (3)
N1	0.030 (2)	0.025 (2)	0.037 (3)	0.0046 (19)	0.0080 (19)	0.001 (2)
C4	0.050 (4)	0.029 (3)	0.050 (4)	0.013 (3)	0.011 (3)	0.011 (3)
O1	0.035 (2)	0.033 (2)	0.047 (2)	0.0046 (17)	0.0123 (18)	−0.0046 (18)
C1	0.053 (4)	0.038 (4)	0.041 (3)	0.010 (3)	0.008 (3)	0.013 (3)
C5	0.046 (4)	0.043 (4)	0.037 (3)	0.012 (3)	0.006 (3)	0.010 (3)
C2	0.052 (4)	0.049 (4)	0.038 (3)	0.010 (3)	0.005 (3)	0.010 (3)
C3	0.039 (3)	0.039 (4)	0.037 (3)	0.007 (3)	0.011 (3)	0.005 (3)

Geometric parameters (Å, º)

Cd1—O1	2.272 (4)	N1—C5	1.337 (8)
Cd1—O1^i	2.384 (4)	N1—O1	1.340 (5)
Cd1—I2	2.7054 (7)	C4—C5	1.360 (8)
Cd1—I1	2.8049 (8)	C4—C3	1.385 (8)
Cd1—I1^ii	2.9650 (7)	C4—H4	0.9300
I1—Cd1^ii	2.9650 (7)	O1—Cd1^i	2.384 (4)
C6—C3	1.487 (8)	C1—C2	1.374 (9)
C6—H6A	0.9600	C1—H1	0.9300
C6—H6B	0.9600	C5—H5	0.9300
C6—H6C	0.9600	C2—C3	1.364 (9)
N1—C1	1.335 (7)	C2—H2	0.9300
O1—Cd1—O1^i	67.55 (15)	C5—N1—O1	120.0 (5)
O1—Cd1—I2	109.61 (11)	C5—C4—C3	121.0 (6)
O1^i—Cd1—I2	96.51 (11)	C5—C4—H4	119.5
O1—Cd1—I1	124.55 (11)	C3—C4—H4	119.5
O1^i—Cd1—I1	88.89 (10)	N1—O1—Cd1	123.9 (3)
I2—Cd1—I1	122.90 (2)	N1—O1—Cd1^i	121.8 (3)
O1—Cd1—I1^ii	88.83 (10)	Cd1—O1—Cd1^i	112.45 (15)
O1^i—Cd1—I1^ii	152.48 (9)	N1—C1—C2	119.9 (6)
I2—Cd1—I1^ii	104.94 (2)	N1—C1—H1	120.1
I1—Cd1—I1^ii	93.61 (2)	C2—C1—H1	120.1
Cd1—I1—Cd1^ii	86.39 (2)	N1—C5—C4	120.5 (5)
C3—C6—H6A	109.5	N1—C5—H5	119.8
C3—C6—H6B	109.5	C4—C5—H5	119.8
H6A—C6—H6B	109.5	C3—C2—C1	121.5 (6)
C3—C6—H6C	109.5	C3—C2—H2	119.3
H6A—C6—H6C	109.5	C1—C2—H2	119.3
H6B—C6—H6C	109.5	C2—C3—C4	116.7 (6)
C1—N1—C5	120.5 (5)	C2—C3—C6	122.7 (6)
C1—N1—O1	119.4 (5)	C4—C3—C6	120.6 (6)
O1—Cd1—I1—Cd1^ii	91.06 (12)	I2—Cd1—O1—Cd1^i	−89.03 (17)
O1^i—Cd1—I1—Cd1^ii	152.57 (10)	I1—Cd1—O1—Cd1^i	71.94 (19)
I2—Cd1—I1—Cd1^ii	−110.39 (3)	I1^ii—Cd1—O1—Cd1^i	165.52 (16)
I1^ii—Cd1—I1—Cd1^ii	0.0	C5—N1—C1—C2	0.3 (9)
C1—N1—O1—Cd1	125.4 (5)	O1—N1—C1—C2	178.6 (5)
C5—N1—O1—Cd1	−56.2 (6)	C1—N1—C5—C4	−0.8 (9)
C1—N1—O1—Cd1^i	−71.6 (6)	O1—N1—C5—C4	−179.2 (5)
C5—N1—O1—Cd1^i	106.8 (5)	C3—C4—C5—N1	1.3 (10)
O1^i—Cd1—O1—N1	164.4 (5)	N1—C1—C2—C3	−0.3 (10)
I2—Cd1—O1—N1	75.4 (4)	C1—C2—C3—C4	0.8 (10)
I1—Cd1—O1—N1	−123.6 (4)	C1—C2—C3—C6	179.5 (6)
I1^ii—Cd1—O1—N1	−30.1 (4)	C5—C4—C3—C2	−1.3 (9)
O1^i—Cd1—O1—Cd1^i	0.0	C5—C4—C3—C6	179.9 (6)

Symmetry codes: (i) −x+1, −y+2, −z+2; (ii) −x, −y+2, −z+2.