Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536803012157/br6105sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S1600536803012157/br6105Isup2.hkl |
Stoichiometric amounts of CdCO_{3} (Merck, p·A.) and H_{3}BO_{3} (10% excess, Merck, p·A.) were ground together finely in an agate mortar and charged in a platinum crucible which was heated to 1353 K over the course of 5 h, kept at that temperature for 1 h and cooled to 973 K over 4 d. The furnace was then shut off. After leaching with boiling demineralized water, colourless single crystals of Cd_{2}B_{2}O_{5}, with mainly plate-like habit and an edge-length of up to 2 mm, were isolated.
The structure was refined with the atomic coordinates of the isomorphous solid solution MnMgB_{2}O_{5} (Utzolino & Bluhm, 1996) as starting parameters. The refined positional parameters were afterwards standardized using the program STRUCTURE-TIDY (Gelato & Parthé, 1987). The highest difference peak is located at a distance of 0.59 Å from Cd1, and the deepest hole 0.63 Å from this atom.
Data collection: CAD-4 Software (Nonius, 1989); cell refinement: CAD-4 Software; data reduction: HELENA implemented in PLATON (Spek, 2003); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ATOMS (Dowty, 2000); software used to prepare material for publication: SHELXL97.
Cd_{2}(B_{2}O_{5}) | Z = 2 |
M_{r} = 326.42 | F(000) = 292 |
Triclinic, P1 | D_{x} = 5.157 Mg m^{−}^{3} |
Hall symbol: -P 1 | Mo Kα radiation, λ = 0.71073 Å |
a = 3.4490 (2) Å | Cell parameters from 25 reflections |
b = 6.3603 (5) Å | θ = 12.4–14.9° |
c = 9.9502 (8) Å | µ = 10.02 mm^{−}^{1} |
α = 105.441 (8)° | T = 293 K |
β = 90.807 (6)° | Plate, colourless |
γ = 91.933 (6)° | 0.22 × 0.14 × 0.07 mm |
V = 210.22 (3) Å^{3} |
Enraf-Nonius CAD-4 diffractometer | 2464 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | R_{int} = 0.018 |
Graphite monochromator | θ_{max} = 39.9°, θ_{min} = 2.1° |
ω/2θ scans | h = −6→6 |
Absorption correction: numerical The crystal shape was optimized by minimizing the R-value of selected ψ-scanned reflections using the program HABITUS (Herrendorf, 1993-97). The habit so derived was used for the numerical absorption correction. | k = −11→11 |
T_{min} = 0.267, T_{max} = 0.473 | l = −17→17 |
5166 measured reflections | 3 standard reflections every 500 min |
2584 independent reflections | intensity decay: none |
Refinement on F^{2} | Primary atom site location: isomorphous structure methods |
Least-squares matrix: full | w = 1/[σ^{2}(F_{o}^{2}) + (0.0307P)^{2} + 0.3225P] where P = (F_{o}^{2} + 2F_{c}^{2})/3 |
R[F^{2} > 2σ(F^{2})] = 0.022 | (Δ/σ)_{max} = 0.001 |
wR(F^{2}) = 0.056 | Δρ_{max} = 2.33 e Å^{−}^{3} |
S = 1.13 | Δρ_{min} = −2.03 e Å^{−}^{3} |
2584 reflections | Extinction correction: SHELXL97 (Sheldrick, 1997), Fc^{*}=kFc[1+0.001xFc^{2}λ^{3}/sin(2θ)]^{-1/4} |
83 parameters | Extinction coefficient: 0.238 (4) |
0 restraints |
Cd_{2}(B_{2}O_{5}) | γ = 91.933 (6)° |
M_{r} = 326.42 | V = 210.22 (3) Å^{3} |
Triclinic, P1 | Z = 2 |
a = 3.4490 (2) Å | Mo Kα radiation |
b = 6.3603 (5) Å | µ = 10.02 mm^{−}^{1} |
c = 9.9502 (8) Å | T = 293 K |
α = 105.441 (8)° | 0.22 × 0.14 × 0.07 mm |
β = 90.807 (6)° |
Enraf-Nonius CAD-4 diffractometer | 2464 reflections with I > 2σ(I) |
Absorption correction: numerical The crystal shape was optimized by minimizing the R-value of selected ψ-scanned reflections using the program HABITUS (Herrendorf, 1993-97). The habit so derived was used for the numerical absorption correction. | R_{int} = 0.018 |
T_{min} = 0.267, T_{max} = 0.473 | 3 standard reflections every 500 min |
5166 measured reflections | intensity decay: none |
2584 independent reflections |
R[F^{2} > 2σ(F^{2})] = 0.022 | 83 parameters |
wR(F^{2}) = 0.056 | 0 restraints |
S = 1.13 | Δρ_{max} = 2.33 e Å^{−}^{3} |
2584 reflections | Δρ_{min} = −2.03 e Å^{−}^{3} |
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 F^{2} against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F^{2}, conventional R-factors R are based on F, with F set to zero for negative F^{2}. The threshold expression of F^{2} > σ(F^{2}) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F^{2} are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger. |
x | y | z | U_{iso}*/U_{eq} | ||
Cd1 | 0.22524 (3) | 0.34751 (2) | 0.593004 (13) | 0.00856 (4) | |
Cd2 | 0.24898 (4) | 0.77837 (2) | 0.125010 (13) | 0.00940 (5) | |
B1 | 0.3291 (6) | 0.3271 (3) | 0.1555 (2) | 0.0081 (3) | |
B2 | 0.6800 (6) | 0.1264 (3) | 0.3200 (2) | 0.0081 (3) | |
O1 | 0.1972 (5) | 0.0792 (2) | 0.69646 (17) | 0.0127 (2) | |
O2 | 0.2570 (5) | 0.2897 (3) | 0.01669 (16) | 0.0128 (2) | |
O3 | 0.2747 (4) | 0.5244 (2) | 0.24790 (16) | 0.0103 (2) | |
O4 | 0.4788 (5) | 0.1526 (2) | 0.20034 (16) | 0.0132 (2) | |
O5 | 0.7276 (4) | 0.2963 (2) | 0.43691 (15) | 0.0097 (2) |
U^{11} | U^{22} | U^{33} | U^{12} | U^{13} | U^{23} | |
Cd1 | 0.00838 (6) | 0.00948 (6) | 0.00881 (6) | 0.00093 (4) | −0.00033 (4) | 0.00410 (4) |
Cd2 | 0.00867 (6) | 0.01101 (6) | 0.00860 (6) | 0.00064 (4) | −0.00024 (4) | 0.00275 (4) |
B1 | 0.0082 (6) | 0.0091 (6) | 0.0072 (6) | 0.0008 (5) | −0.0005 (5) | 0.0027 (5) |
B2 | 0.0092 (6) | 0.0076 (6) | 0.0078 (6) | 0.0020 (5) | 0.0009 (5) | 0.0025 (5) |
O1 | 0.0181 (6) | 0.0097 (5) | 0.0122 (6) | 0.0055 (4) | 0.0028 (5) | 0.0055 (4) |
O2 | 0.0111 (5) | 0.0194 (6) | 0.0081 (5) | 0.0015 (5) | −0.0006 (4) | 0.0038 (5) |
O3 | 0.0118 (5) | 0.0092 (5) | 0.0095 (5) | 0.0027 (4) | 0.0002 (4) | 0.0015 (4) |
O4 | 0.0212 (6) | 0.0078 (5) | 0.0101 (5) | 0.0024 (4) | −0.0057 (5) | 0.0016 (4) |
O5 | 0.0107 (5) | 0.0098 (5) | 0.0080 (5) | 0.0010 (4) | −0.0005 (4) | 0.0013 (4) |
Cd1—O1 | 2.2152 (15) | Cd2—O1^{iii} | 2.3787 (16) |
Cd1—O5^{i} | 2.2544 (15) | Cd2—O4^{vii} | 2.4004 (15) |
Cd1—O3^{ii} | 2.2993 (15) | Cd2—O1^{ii} | 2.5603 (18) |
Cd1—O5 | 2.3162 (15) | Cd2—Cd2^{iv} | 3.4490 (2) |
Cd1—O5^{ii} | 2.3631 (15) | Cd2—Cd2^{i} | 3.4490 (2) |
Cd1—O3^{iii} | 2.3722 (15) | B1—O2 | 1.356 (3) |
Cd1—Cd1^{iii} | 3.4112 (3) | B1—O3 | 1.364 (2) |
Cd1—Cd1^{iv} | 3.4490 (2) | B1—O4 | 1.411 (3) |
Cd1—Cd1^{i} | 3.4490 (2) | B2—O1^{viii} | 1.357 (2) |
Cd2—O2^{v} | 2.1853 (16) | B2—O5 | 1.364 (3) |
Cd2—O2^{vi} | 2.2071 (16) | B2—O4 | 1.421 (3) |
Cd2—O3 | 2.2742 (15) | ||
O1—Cd1—O5^{i} | 108.32 (6) | O2^{vi}—Cd2—O1^{iii} | 167.32 (6) |
O1—Cd1—O3^{ii} | 82.70 (6) | O3—Cd2—O1^{iii} | 79.56 (5) |
O5^{i}—Cd1—O3^{ii} | 167.91 (6) | O2^{v}—Cd2—O4^{vii} | 116.07 (6) |
O1—Cd1—O5 | 110.00 (5) | O2^{vi}—Cd2—O4^{vii} | 88.75 (6) |
O5^{i}—Cd1—O5 | 97.97 (6) | O3—Cd2—O4^{vii} | 127.06 (5) |
O3^{ii}—Cd1—O5 | 82.35 (5) | O1^{iii}—Cd2—O4^{vii} | 79.34 (6) |
O1—Cd1—O5^{ii} | 160.36 (6) | O2^{v}—Cd2—O1^{ii} | 170.77 (6) |
O5^{i}—Cd1—O5^{ii} | 84.78 (5) | O2^{vi}—Cd2—O1^{ii} | 81.11 (5) |
O3^{ii}—Cd1—O5^{ii} | 83.31 (5) | O3—Cd2—O1^{ii} | 75.95 (5) |
O5—Cd1—O5^{ii} | 81.63 (5) | O1^{iii}—Cd2—O1^{ii} | 88.50 (5) |
O1—Cd1—O3^{iii} | 80.89 (5) | O4^{vii}—Cd2—O1^{ii} | 55.55 (5) |
O5^{i}—Cd1—O3^{iii} | 82.07 (5) | O2—B1—O3 | 122.46 (17) |
O3^{ii}—Cd1—O3^{iii} | 95.16 (5) | O2—B1—O4 | 116.53 (17) |
O5—Cd1—O3^{iii} | 168.29 (5) | O3—B1—O4 | 120.97 (17) |
O5^{ii}—Cd1—O3^{iii} | 86.72 (5) | O1^{viii}—B2—O5 | 126.35 (18) |
O2^{v}—Cd2—O2^{vi} | 103.48 (6) | O1^{viii}—B2—O4 | 112.94 (16) |
O2^{v}—Cd2—O3 | 110.08 (6) | O5—B2—O4 | 120.70 (17) |
O2^{vi}—Cd2—O3 | 104.69 (6) | B1—O4—B2 | 136.82 (16) |
O2^{v}—Cd2—O1^{iii} | 85.84 (6) |
Symmetry codes: (i) x−1, y, z; (ii) −x+1, −y+1, −z+1; (iii) −x, −y+1, −z+1; (iv) x+1, y, z; (v) −x, −y+1, −z; (vi) −x+1, −y+1, −z; (vii) x, y+1, z; (viii) −x+1, −y, −z+1. |
Experimental details
Crystal data | |
Chemical formula | Cd_{2}(B_{2}O_{5}) |
M_{r} | 326.42 |
Crystal system, space group | Triclinic, P1 |
Temperature (K) | 293 |
a, b, c (Å) | 3.4490 (2), 6.3603 (5), 9.9502 (8) |
α, β, γ (°) | 105.441 (8), 90.807 (6), 91.933 (6) |
V (Å^{3}) | 210.22 (3) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm^{−}^{1}) | 10.02 |
Crystal size (mm) | 0.22 × 0.14 × 0.07 |
Data collection | |
Diffractometer | Enraf-Nonius CAD-4 diffractometer |
Absorption correction | Numerical The crystal shape was optimized by minimizing the R-value of selected ψ-scanned reflections using the program HABITUS (Herrendorf, 1993-97). The habit so derived was used for the numerical absorption correction. |
T_{min}, T_{max} | 0.267, 0.473 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 5166, 2584, 2464 |
R_{int} | 0.018 |
(sin θ/λ)_{max} (Å^{−}^{1}) | 0.903 |
Refinement | |
R[F^{2} > 2σ(F^{2})], wR(F^{2}), S | 0.022, 0.056, 1.13 |
No. of reflections | 2584 |
No. of parameters | 83 |
Δρ_{max}, Δρ_{min} (e Å^{−}^{3}) | 2.33, −2.03 |
Computer programs: CAD-4 Software (Nonius, 1989), CAD-4 Software, HELENA implemented in PLATON (Spek, 2003), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), ATOMS (Dowty, 2000), SHELXL97.
Cd1—O1 | 2.2152 (15) | Cd2—O1^{iii} | 2.3787 (16) |
Cd1—O5^{i} | 2.2544 (15) | Cd2—O4^{vi} | 2.4004 (15) |
Cd1—O3^{ii} | 2.2993 (15) | Cd2—O1^{ii} | 2.5603 (18) |
Cd1—O5 | 2.3162 (15) | B1—O2 | 1.356 (3) |
Cd1—O5^{ii} | 2.3631 (15) | B1—O3 | 1.364 (2) |
Cd1—O3^{iii} | 2.3722 (15) | B1—O4 | 1.411 (3) |
Cd2—O2^{iv} | 2.1853 (16) | B2—O1^{vii} | 1.357 (2) |
Cd2—O2^{v} | 2.2071 (16) | B2—O5 | 1.364 (3) |
Cd2—O3 | 2.2742 (15) | B2—O4 | 1.421 (3) |
O2—B1—O3 | 122.46 (17) | O1^{vii}—B2—O4 | 112.94 (16) |
O2—B1—O4 | 116.53 (17) | O5—B2—O4 | 120.70 (17) |
O3—B1—O4 | 120.97 (17) | B1—O4—B2 | 136.82 (16) |
O1^{vii}—B2—O5 | 126.35 (18) |
Symmetry codes: (i) x−1, y, z; (ii) −x+1, −y+1, −z+1; (iii) −x, −y+1, −z+1; (iv) −x, −y+1, −z; (v) −x+1, −y+1, −z; (vi) x, y+1, z; (vii) −x+1, −y, −z+1. |
Cd_{2}B_{2}O_{5}, (I), is an interesting host material for luminescent applications when doped with tranistion metal or RE ions. Its structure has been determined by Sokolova et al. (1979) and was described in space group P1. Comparison of the symmetry and lattice parameters of other M_{2}B_{2}O_{5} members [M = Co (Berger, 1950), Mg, Fe, Mn (Block et al., 1959), Mg (Guo et al., 1995a)] and solid solutions MM'B_{2}O_{5} [M = Mn, M' = Mg, Co (Utzolino & Bluhm, 1996); M = Zn, M' = Co, Ni (Busche & Bluhm, 1995)], which all crystallize with similar lattice parameters in the centrosymmetric space group P1, suggested a possible change in the space-group symmetry. Therefore the published atomic coordinates (Sokolova et al., 1979) were checked with the PLATON program (Spek, 2003) which, in fact, indicated a centre of symmetry within the default tolerances of the program. For experimental proof, single crystals of Cd_{2}B_{2}O_{5} were grown and the structure was re-determined in space group P1.
Cd_{2}B_{2}O_{5} crystallizes isotypically with the triclinic representatives of the M_{2}B_{2}O_{5} family mentioned above. For all these structures, two angles close to 90° are observed, indicating a possible phase transition to the monoclinic crystal system. At least for Mg_{2}B_{2}O_{5}, a synthetic monoclinic polymorph is described (Guo et al., 1995b) which is identical to the mineral Suanite (Takeuchi, 1952).
The crystal structure is composed of two crystallographically independent and distorted [CdO_{6}] octahedra, and B_{2}O_{5} groups as the main building units. The [CdO_{6}] octahedra have mean Cd—O distances of 2.303 Å (Cd1) and 2.334 Å (Cd2) and build chains running parallel to the [100] direction by edge-sharing (Fig. 1). Four of these chains are connected to form ribbons along the [011] direction (Fig. 2). Adjacent ribbons are held together by the interstitial B_{2}O_{5} anions.
As in other diborate structures with two condensed BO_{3} triangles, the corresponding polyhedra are substantially distorted. The distances from B to the bridging atom O4 are considerably longer than to the terminal atoms O1, O2, O3 and O5 (see Table 1). The B—O distances for the two independent BO_{3} triangles are very similar, and the average B—O distances ¯d(B1—O) = 1.377 Å and ¯d(B2—O) = 1.381 Å are in good agreement with the data for many other borate structures with BO_{3} groups (Zobetz, 1982). The B_{2}O_{5} anion (Fig. 3) deviates significantly from coplanarity; the dihedral angle between the two slanting BO_{3} triangles is 13.1 (1)°.
The O atoms O1, O3 and O5 exhibit coordination number 4 and are each surrounded by three Cd and one B atom. O2 has three coordination partners (2 x Cd and B) with two short Cd—O distances and a short B—O distance. O4 is the bridging atom of the diborate group and has an additional Cd atom with a long Cd—O distance in its coordination environment.