Cd₃Se₃O₁₀, isotypic with its mercury analogue

The mixed-valent Se^IV/VI compound tricadmium(II) bis-[selenite(IV)] selenate(VI), Cd₃(SeO₃)₂SeO₄, contains three crystallographically inequivalent Cd^II cations, one Se^VIO₄ tetrahedron and two independent Se^IVO₃ pyramids corresponding to the formula Cd₃(SeO₃)₂(SeO₄). The structure is composed of a three-dimensional network with channels extending parallel to the b axis. Distances and angles within the three [CdO_x] polyhedra (x = 6, 8), as well as within the anionic framework, deviate only slightly from those of the isotypic mercury analogue, Hg₃Se₃O₁₀.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](Se-O) = 0.004 Å
• R factor = 0.018
• wR factor = 0.044
• Data-to-parameter ratio = 17.1

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


 Alert Level A:



DIFF_019  Alert A _diffrn_standards_number is missing
          Number of standards used in measurement.

Author response: An area detector system (CCD camera) was used for data collection. No standard reflections were measured.

DIFF_020  Alert A _diffrn_standards_interval_count and
          _diffrn_standards_interval_time are missing. Number of measurements
          between standards or time (min) between standards.

Author response: An area detector system (CCD camera) was used for data collection. No standard reflections were measured.

DIFF_022  Alert A _diffrn_standards_decay_% is missing
          Percentage decrease in standards intensity.

Author response: An area detector system (CCD camera) was used for data collection. No standard reflections were measured.

General Notes



ABSTM_02  When printed, the submitted absorption T values will be replaced
          by the scaled T values. Since the ratio of scaled T's is
          identical to the ratio of reported T values, the scaling does
          not imply a change to the absorption corrections used in the
          study.
          Ratio of Tmax expected/reported      0.905
          Tmax scaled      0.468 Tmin scaled      0.105

REFLT_03
         From the CIF: _diffrn_reflns_theta_max           30.47
         From the CIF: _reflns_number_total               2497
         Count of symmetry unique reflns         1522
         Completeness (_total/calc)            164.06%
         TEST3: Check Friedels for noncentro structure
         Estimate of Friedel pairs measured       975
         Fraction of Friedel pairs measured     0.641
         Are heavy atom types Z>Si present          yes
          Please check that the estimate of the number of Friedel pairs is
          correct. If it is not, please give the correct count in the
          _publ_section_exptl_refinement section of the submitted CIF.


 3 Alert Level A = Potentially serious problem

 0 Alert Level B = Potential problem

 0 Alert Level C = Please check

---

S1. Comment

Numerous phases within the system Cd–Se–O–(H) are listed in standard handbooks about cadmium and its compounds (Gmelins Handbuch der Anorganischen Chemie, 1959), and most of these compounds have been crystallographically well characterized in the meantime. For the anhydrous selenites(IV) α-CdSeO₃, β-CdSeO₃ (Valkonen, 1994a) and CdSe₂O₅ (Valkonen, 1994b), for the hydrous selenites(IV) CdSeO₃(H₂O) (Bäumer et al., 1998), Cd₃(HSeO₃)₂(SeO₃)₂ (Valkonen, 1994b) and (CdSeO₃)₄(H₂O)₃ (Valkonen, 1994a), as well as for the selenates(VI) CdSeO₄(H₂O) (Stålhandske, 1981), CdSeO₄, Cd(HSeO₄)₂(H₂O) (Morozov et al., 1999) and CdSeO₄(H₂O)₂ (Weil, 2002), full structure analyses based on single-crystal data have been reported. Powder data are given for the tetraselenite(IV) Cd₃Se₄O₁₁ (Markovskii & Sapozhnikov, 1961).

Cd₃Se₃O₁₀ is reported for the first time and reveals isotypism with its mercury analogue, Hg₃Se₃O₁₀, whose preparation and crystal structure was recently described in detail (Weil & Kolitsch, 2002). The crystal structure is composed of three independent Cd^II cations, two Se^IVO₃ groups and a Se^VIO₄ group as the main building units. Cd₃Se₃O₁₀ is the first Cd compound to contain both selenium(IV) and selenium(VI) oxo groups within the structure.

The building units are linked via common oxygen atoms to form a three-dimensional network. Edge-sharing [CdO₈] polyhedra build layers ²_∞[CdO_8/2] parallel to the bc plane which are bridged by the Se^IVO₃ groups. Two adjacent layers are connected via Se^VIO₄ tetrahedra and [Cd3O₆] polyhedra along the a axis to form channels extending parallel to the b axis, as depicted in Fig. 1. The selenite(IV) groups are situated above and below the cavities of the ²_∞[CdO_8/2] layers with the non-bonding orbitals, directed towards each other into the cavities of the structure.

If bonding interactions are being considered for distances d(Cd—O) < 3.0 Å, Cd1 and Cd2 are eight-coordinate with four short, two medium and two longer distances, resulting in a [4 + 2+2]-coordination with similar mean distances of ¯d(Cd1—O) = 2.475 Å and ¯d(Cd2—O) = 2.484 Å. Cd3 shows a [4 + 2]-coordination, with a slightly shorter mean of ¯d(Cd3—O) = 2.400 Å.

Both selenite(IV) (Se1 and Se2) and selenate(VI) (Se3) groups display the well known geometry of a trigonal pyramid [Se1: ¯d(Se1—O) = 1.702 Å, mean angle: 97.5°; Se2: ¯d(Se2—O) = 1.704 Å, mean angle 97.9°] and a tetrahedron [¯d(Se3—O) = 1.638 Å, mean angle 109.5°], respectively.

The bond-valence sums, as calculated with the parameters given by Brese and O'Keeffe (1991), are in agreement with the expected values: Cd1 (CN = 8, 1.972), Cd2 (8, 2.082), Cd3 (6, 2.016), Se1 (3, 4.032), Se2 (3, 4.010), Se3 (4, 6.013), O1 (3, 2.133), O2 (3, 2.167), O3 (4, 2.099), O4 (4, 2.079), O5 (4, 2.163), O6 (4, 2.155), O7 (2, 1.892), O8 (2, 1.835), O9 (3, 1.787), O10 (3, 1.813). The O atoms which belong to selenite(IV) groups are O1–O6, and the O atoms of the selenate(VI) group are O7–O10.

S2. Experimental

Experiments intended to prepare single crystals of compounds with the general formula (CdSeO₄)_x(HgO)_y(H₂O)_z, with x = 1, y = 1, 1.5 or 2 and z = 0 or 1 (Denk & Leschhorn, 1966), yielded colourless crystals with mostly rod-like habit of the title compound and colourless plates of composition (CdSeO₄)(HgO)(H₂O) [space group P2/n, a = 7.9895 (18) Å, b = 6.3307 (6) Å, c = 10.5738 (11) Å and β = 102.795 (2)°; Weil, 2002] by reacting HgO and CdSeO₄(H₂O)₂ in the molar ratio 1:2 in demineralized water under hydrothermal conditions (teflon-lined steel autoclave, 523 K, 6 d).

S3. Refinement

Systematic absences k = 2n+1 for the (0k0) reflections and similar lattice parameters revealed isotypism with the mercury analogue, Hg₃Se₃O₁₀. The crystal structure was therefore refined with the atomic coordinates of the mercury compound as starting parameters. Refinement of the occupation factors did not indicate any incorporation of Hg^II into the structure.

Computing details

Data collection: SMART (Siemens, 1996); cell refinement: SAINT (Siemens, 1996); data reduction: SAINT; program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ATOMS for Windows (Dowty, 2000); software used to prepare material for publication: SHELXL97.

Figures

Fig. 1. Projection of the crystal structure along [010].

Tricadmium(II) bis(selenite(IV)) selenate(VI)

Crystal data

Cd3(SeO3)2SeO4	F(000) = 652
Mr = 734.08	Dx = 5.352 Mg m^−3
Monoclinic, P21	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2yb	Cell parameters from 4083 reflections
a = 8.3031 (8) Å	θ = 2.7–30.5°
b = 5.3377 (5) Å	µ = 18.97 mm^−1
c = 10.8485 (11) Å	T = 293 K
β = 108.659 (2)°	Rod, colourless
V = 455.53 (8) Å^3	0.20 × 0.04 × 0.04 mm
Z = 2

Data collection

Siemens SMART diffractometer	2497 independent reflections
Radiation source: fine-focus sealed tube	2402 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.023
ω scans	θmax = 30.5°, θmin = 2.0°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −11→11
Tmin = 0.116, Tmax = 0.518	k = −7→7
4516 measured reflections	l = −14→14

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	w = 1/[σ^2(Fo^2)]
R[F^2 > 2σ(F^2)] = 0.018	(Δ/σ)max = 0.001
wR(F^2) = 0.044	Δρmax = 0.97 e Å^−3
S = 1.00	Δρmin = −0.79 e Å^−3
2497 reflections	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
146 parameters	Extinction coefficient: 0.0065 (3)
1 restraint	Absolute structure: Flack (1983), 0000 Friedel pairs
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.080 (9)

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	−0.00382 (4)	0.25150 (8)	0.12793 (2)	0.01258 (7)
Cd2	−0.01861 (4)	0.25949 (8)	0.61730 (2)	0.01527 (8)
Cd3	0.36338 (4)	0.73845 (9)	0.20432 (3)	0.02092 (9)
Se1	0.25424 (5)	0.22642 (10)	0.95611 (4)	0.01246 (10)
Se2	0.26984 (5)	0.28363 (10)	0.42598 (4)	0.01253 (10)
Se3	0.65260 (5)	0.24831 (11)	0.28455 (3)	0.01370 (9)
O1	0.0935 (4)	0.1330 (6)	0.8235 (3)	0.0204 (7)
O2	0.1159 (4)	0.3891 (6)	0.4852 (3)	0.0192 (7)
O3	0.1592 (4)	0.0678 (6)	0.3134 (3)	0.0167 (7)
O4	0.1569 (4)	0.4555 (6)	0.0177 (3)	0.0161 (7)
O5	0.2256 (5)	−0.0108 (6)	0.0509 (3)	0.0232 (8)
O6	0.2527 (5)	0.5314 (7)	0.3248 (3)	0.0245 (8)
O7	0.5285 (4)	0.0451 (7)	0.3226 (3)	0.0246 (8)
O8	0.5350 (5)	0.4382 (7)	0.1709 (3)	0.0247 (8)
O9	0.7526 (5)	0.4118 (7)	0.4124 (3)	0.0243 (8)
O10	0.7827 (5)	0.0992 (6)	0.2245 (3)	0.0235 (8)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cd1	0.01555 (14)	0.01217 (17)	0.00942 (12)	0.00015 (19)	0.00315 (9)	0.00052 (15)
Cd2	0.02123 (16)	0.01518 (17)	0.01064 (12)	−0.0002 (2)	0.00685 (10)	0.00057 (16)
Cd3	0.01811 (16)	0.02101 (19)	0.02167 (14)	−0.0012 (2)	0.00359 (11)	0.01152 (18)
Se1	0.01315 (18)	0.0126 (2)	0.01091 (16)	−0.0003 (2)	0.00281 (13)	0.00033 (18)
Se2	0.01206 (18)	0.0140 (2)	0.01093 (16)	−0.00041 (18)	0.00278 (13)	0.00109 (18)
Se3	0.01202 (18)	0.0174 (2)	0.01099 (15)	0.0002 (3)	0.00273 (13)	−0.0022 (2)
O1	0.0250 (19)	0.0213 (17)	0.0106 (14)	−0.0049 (14)	−0.0001 (13)	0.0005 (12)
O2	0.0201 (18)	0.0193 (16)	0.0229 (16)	0.0075 (13)	0.0134 (14)	0.0079 (13)
O3	0.0212 (18)	0.0155 (16)	0.0103 (14)	−0.0041 (13)	0.0009 (13)	−0.0011 (12)
O4	0.0196 (19)	0.0172 (17)	0.0129 (15)	0.0050 (13)	0.0071 (14)	−0.0001 (12)
O5	0.028 (2)	0.0199 (18)	0.0148 (16)	−0.0018 (15)	−0.0022 (15)	0.0088 (14)
O6	0.026 (2)	0.0203 (18)	0.033 (2)	0.0038 (14)	0.0174 (17)	0.0133 (15)
O7	0.0193 (19)	0.032 (2)	0.0236 (17)	−0.0094 (15)	0.0088 (15)	0.0047 (15)
O8	0.022 (2)	0.030 (2)	0.0207 (17)	0.0053 (15)	0.0041 (14)	0.0102 (14)
O9	0.029 (2)	0.0227 (18)	0.0164 (16)	0.0000 (15)	−0.0003 (15)	−0.0103 (13)
O10	0.0218 (19)	0.0232 (19)	0.0316 (19)	−0.0018 (14)	0.0169 (16)	−0.0069 (15)

Geometric parameters (Å, º)

Cd1—O3	2.258 (3)	Se1—O5^ix	1.696 (3)
Cd1—O1^i	2.287 (3)	Se1—O4^ix	1.715 (3)
Cd1—O4^ii	2.307 (3)	Se1—Cd1^v	3.2199 (7)
Cd1—O4	2.327 (3)	Se1—Cd1^ix	3.2617 (6)
Cd1—O10^iii	2.468 (4)	Se1—Cd1^i	3.4346 (7)
Cd1—O5^iv	2.545 (4)	Se1—Cd3^x	3.6462 (7)
Cd1—O5	2.703 (4)	Se1—Cd3^ix	3.7390 (7)
Cd1—O6	2.902 (4)	Se1—Cd3^vii	4.0803 (6)
Cd2—O2	2.191 (3)	Se2—O6	1.695 (3)
Cd2—O1	2.235 (3)	Se2—O2	1.700 (3)
Cd2—O3^i	2.280 (3)	Se2—O3	1.716 (3)
Cd2—O2^v	2.286 (3)	Se2—Cd2^i	3.2244 (7)
Cd2—O6^v	2.537 (4)	Se2—Cd2^v	3.4310 (8)
Cd2—O9^iii	2.551 (3)	Se2—Cd3^xi	4.0061 (7)
Cd2—O10^vi	2.814 (4)	Se2—Cd3^vii	4.1956 (6)
Cd2—O9^vii	2.980 (4)	Se3—O9	1.624 (3)
Cd3—O6	2.132 (3)	Se3—O10	1.636 (3)
Cd3—O5^viii	2.157 (3)	Se3—O7	1.637 (3)
Cd3—O8	2.250 (4)	Se3—O8	1.653 (3)
Cd3—O7^viii	2.254 (4)	Se3—Cd3^xi	3.5488 (6)
Cd3—O4	2.664 (3)	Se3—Cd1^xii	3.7586 (5)
Cd3—O3^viii	2.940 (3)	Se3—Cd2^xii	3.7658 (5)
Cd3—Se3	3.4687 (6)	Se3—Cd2^vii	3.8867 (7)
Cd3—Se3^viii	3.5488 (6)	Se3—Cd2^vi	3.9679 (8)
Se1—O1	1.694 (3)
O3—Cd1—O1^i	109.14 (11)	O6^v—Cd2—O9^iii	87.29 (13)
O3—Cd1—O4^ii	110.77 (11)	O2—Cd2—O10^vi	78.15 (12)
O1^i—Cd1—O4^ii	128.24 (12)	O1—Cd2—O10^vi	66.32 (10)
O3—Cd1—O4	112.45 (11)	O3^i—Cd2—O10^vi	70.35 (11)
O1^i—Cd1—O4	89.10 (12)	O2^v—Cd2—O10^vi	157.33 (11)
O4^ii—Cd1—O4	104.43 (8)	O6^v—Cd2—O10^vi	126.67 (10)
O3—Cd1—O10^iii	77.66 (12)	O9^iii—Cd2—O10^vi	120.34 (11)
O1^i—Cd1—O10^iii	82.20 (12)	O2—Cd2—O9^vii	64.89 (10)
O4^ii—Cd1—O10^iii	75.64 (11)	O1—Cd2—O9^vii	80.44 (11)
O4—Cd1—O10^iii	168.54 (12)	O3^i—Cd2—O9^vii	163.84 (10)
O3—Cd1—O5^iv	167.67 (13)	O2^v—Cd2—O9^vii	64.36 (11)
O1^i—Cd1—O5^iv	61.47 (10)	O6^v—Cd2—O9^vii	112.38 (12)
O4^ii—Cd1—O5^iv	73.36 (11)	O9^iii—Cd2—O9^vii	118.37 (8)
O4—Cd1—O5^iv	76.64 (13)	O10^vi—Cd2—O9^vii	94.12 (10)
O10^iii—Cd1—O5^iv	92.58 (13)	O6—Cd3—O5^viii	124.66 (15)
O3—Cd1—O5	76.67 (11)	O6—Cd3—O8	98.57 (13)
O1^i—Cd1—O5	147.81 (12)	O5^viii—Cd3—O8	121.65 (13)
O4^ii—Cd1—O5	73.84 (12)	O6—Cd3—O7^viii	109.30 (14)
O4—Cd1—O5	60.47 (10)	O5^viii—Cd3—O7^viii	93.69 (14)
O10^iii—Cd1—O5	129.31 (11)	O8—Cd3—O7^viii	107.93 (13)
O5^iv—Cd1—O5	115.60 (8)	O6—Cd3—O4	82.71 (13)
O3—Cd1—O6	58.54 (10)	O5^viii—Cd3—O4	73.26 (11)
O1^i—Cd1—O6	65.70 (11)	O8—Cd3—O4	76.14 (12)
O4^ii—Cd1—O6	166.04 (11)	O7^viii—Cd3—O4	166.09 (11)
O4—Cd1—O6	74.39 (10)	O6—Cd3—O3^viii	69.28 (12)
O10^iii—Cd1—O6	108.36 (10)	O5^viii—Cd3—O3^viii	73.00 (12)
O5^iv—Cd1—O6	119.09 (11)	O8—Cd3—O3^viii	165.28 (10)
O5—Cd1—O6	94.03 (10)	O7^viii—Cd3—O3^viii	70.17 (11)
O2—Cd2—O1	127.85 (13)	O4—Cd3—O3^viii	109.32 (9)
O2—Cd2—O3^i	114.19 (12)	O1—Se1—O5^ix	94.02 (16)
O1—Cd2—O3^i	88.92 (11)	O1—Se1—O4^ix	101.51 (16)
O2—Cd2—O2^v	97.44 (9)	O5^ix—Se1—O4^ix	96.94 (16)
O1—Cd2—O2^v	101.23 (12)	O6—Se2—O2	93.95 (16)
O3^i—Cd2—O2^v	130.27 (12)	O6—Se2—O3	98.51 (17)
O2—Cd2—O6^v	154.73 (12)	O2—Se2—O3	101.27 (17)
O1—Cd2—O6^v	73.39 (12)	O9—Se3—O10	112.29 (18)
O3^i—Cd2—O6^v	75.58 (13)	O9—Se3—O7	109.40 (18)
O2^v—Cd2—O6^v	61.69 (11)	O10—Se3—O7	109.09 (19)
O2—Cd2—O9^iii	73.90 (12)	O9—Se3—O8	109.05 (19)
O1—Cd2—O9^iii	157.54 (13)	O10—Se3—O8	107.99 (18)
O3^i—Cd2—O9^iii	74.96 (11)	O7—Se3—O8	108.96 (17)
O2^v—Cd2—O9^iii	78.64 (12)

Symmetry codes: (i) −x, y+1/2, −z+1; (ii) −x, y−1/2, −z; (iii) x−1, y, z; (iv) −x, y+1/2, −z; (v) −x, y−1/2, −z+1; (vi) −x+1, y+1/2, −z+1; (vii) −x+1, y−1/2, −z+1; (viii) x, y+1, z; (ix) x, y, z+1; (x) x, y−1, z+1; (xi) x, y−1, z; (xii) x+1, y, z.