Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270104033396/bc1065sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270104033396/bc1065Isup2.hkl |
The starting materials for the synthesis of β-Gd2B4O9 in this work were a 2:1 molar mixture of B2O3 [from H3BO3 (99.8%, Merck, Darmstadt) fired at 873 K] and Gd2O3 (99.9%). The materials were compressed and heated via a multi-anvil assembly. Details concerning the construction of the assembly have been published previously (Huppertz, 2001, 2004; Walker et al., 1990; Walker, 1991; Rubie, 1999). For the synthesis of β-Gd2B4O9, the 18/11 assembly was compressed within 1 h to 3 GPa and heated to 1223 K in the following 10 min. After holding this temperature for 10 min, the sample was cooled down to room temperature in another 10 min. After decompression, the sample assembly was broken apart and the sample was carefully separated from the surrounding boron nitride. β-Gd2B4O9 was obtained as a single-phase crystalline product (yield 75 mg per run). It crystallizes as small colourless parallelepiped-like crystals which are stable in air and water.
The highest peak is 2.30 e Å−3 at (0.0310, 0.1375, 0.0790) (0.86 Å from atom B4). The deepest hole is −2.93 e Å−3 at (0.4014, 0.9072, 0.7750) (0.58 Å from atom Gd2).
Data collection: COLLECT (Nonius, 1997-2000); cell refinement: HKL SCALEPACK (Otwinowski & Minor, 1997); data reduction: HKL DENZO (Otwinowski & Minor, 1997) and SCALEPACK; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: DIAMOND (Brandenburg & Berndt, 1999); software used to prepare material for publication: enCIFer (Allen et al., 2004) and SHELXL97.
Fig. 1. The crystal structure of β-Gd2B4O9, viewed along [010]. | |
Fig. 2. The crystal structure of β-Gd2B4O9, viewed along [001]. |
Gd2B4O9 | Z = 2 |
Mr = 501.74 | F(000) = 440 |
Triclinic, P1 | Dx = 5.880 Mg m−3 |
Hall symbol: -P 1 | Mo Kα radiation, λ = 0.71073 Å |
a = 6.1973 (10) Å | Cell parameters from 4198 reflections |
b = 6.4757 (10) Å | θ = 3.1–37.8° |
c = 7.5249 (10) Å | µ = 23.23 mm−1 |
α = 102.386 (10)° | T = 293 K |
β = 96.983 (10)° | Block, colourless |
γ = 102.544 (10)° | 0.05 × 0.04 × 0.02 mm |
V = 283.41 (8) Å3 |
Nonius KappaCCD area-detector diffractometer | 3007 independent reflections |
Radiation source: fine-focus sealed tube | 2538 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.045 |
Detector resolution: 9 pixels mm-1 | θmax = 37.9°, θmin = 3.3° |
95 mm CCD camera on κ–goniostat scans | h = −10→10 |
Absorption correction: numerical (HABITUS; Herrendorf & Bärnighausen, 1997) | k = −11→10 |
Tmin = 0.365, Tmax = 0.695 | l = −12→12 |
10001 measured reflections |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.026 | w = 1/[σ2(Fo2) + (0.009P)2] where P = (Fo2 + 2Fc2)/3 |
wR(F2) = 0.050 | (Δ/σ)max = 0.001 |
S = 1.00 | Δρmax = 2.30 e Å−3 |
3007 reflections | Δρmin = −2.93 e Å−3 |
137 parameters | Extinction correction: SHELXL97 (Sheldrick, 1997), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
0 restraints | Extinction coefficient: 0.0185 (4) |
Gd2B4O9 | γ = 102.544 (10)° |
Mr = 501.74 | V = 283.41 (8) Å3 |
Triclinic, P1 | Z = 2 |
a = 6.1973 (10) Å | Mo Kα radiation |
b = 6.4757 (10) Å | µ = 23.23 mm−1 |
c = 7.5249 (10) Å | T = 293 K |
α = 102.386 (10)° | 0.05 × 0.04 × 0.02 mm |
β = 96.983 (10)° |
Nonius KappaCCD area-detector diffractometer | 3007 independent reflections |
Absorption correction: numerical (HABITUS; Herrendorf & Bärnighausen, 1997) | 2538 reflections with I > 2σ(I) |
Tmin = 0.365, Tmax = 0.695 | Rint = 0.045 |
10001 measured reflections |
R[F2 > 2σ(F2)] = 0.026 | 137 parameters |
wR(F2) = 0.050 | 0 restraints |
S = 1.00 | Δρmax = 2.30 e Å−3 |
3007 reflections | Δρmin = −2.93 e Å−3 |
Experimental. Crystal embedded in oil and mounted with wax |
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. |
x | y | z | Uiso*/Ueq | ||
Gd1 | 0.88767 (2) | 0.67782 (2) | 0.35900 (2) | 0.00561 (5) | |
Gd2 | 0.54641 (2) | 0.09170 (2) | 0.28415 (2) | 0.00539 (5) | |
O1 | 0.5065 (4) | 0.7874 (4) | 1.0184 (3) | 0.0067 (4) | |
O2 | 0.4229 (4) | 0.1848 (4) | 0.5584 (3) | 0.0061 (4) | |
O3 | 0.7621 (4) | 0.2639 (4) | 0.7902 (3) | 0.0057 (4) | |
O4 | 0.7785 (4) | 0.4065 (4) | 0.5249 (3) | 0.0062 (4) | |
O5 | 1.1388 (4) | 0.7172 (4) | 0.8599 (3) | 0.0072 (4) | |
O6 | 0.5415 (4) | 0.5375 (4) | 0.7492 (3) | 0.0066 (4) | |
O7 | 0.7725 (4) | 0.5695 (4) | 1.0388 (3) | 0.0054 (4) | |
O8 | 0.8140 (4) | 0.8660 (4) | 0.8832 (3) | 0.0077 (4) | |
O9 | 1.0648 (4) | 0.9515 (4) | 0.6771 (3) | 0.0075 (4) | |
B1 | 0.7317 (6) | 0.3353 (6) | 0.9806 (5) | 0.0052 (6) | |
B2 | 0.6624 (6) | 0.6787 (6) | 0.9262 (5) | 0.0055 (6) | |
B3 | 0.6261 (6) | 0.3582 (6) | 0.6521 (5) | 0.0059 (6) | |
B4 | 1.0056 (6) | 0.8510 (6) | 0.8130 (5) | 0.0063 (6) |
U11 | U22 | U33 | U12 | U13 | U23 | |
Gd1 | 0.00608 (8) | 0.00597 (8) | 0.00516 (8) | 0.00187 (6) | 0.00119 (6) | 0.00170 (6) |
Gd2 | 0.00608 (8) | 0.00550 (8) | 0.00457 (8) | 0.00138 (6) | 0.00112 (6) | 0.00119 (6) |
O1 | 0.0059 (10) | 0.0063 (10) | 0.0067 (11) | 0.0008 (8) | 0.0009 (8) | −0.0003 (8) |
O2 | 0.0066 (10) | 0.0078 (10) | 0.0037 (10) | 0.0018 (8) | 0.0014 (8) | 0.0007 (8) |
O3 | 0.0075 (10) | 0.0062 (10) | 0.0030 (10) | 0.0021 (8) | 0.0000 (8) | 0.0005 (8) |
O4 | 0.0054 (10) | 0.0060 (10) | 0.0072 (11) | 0.0006 (8) | 0.0011 (8) | 0.0026 (8) |
O5 | 0.0077 (10) | 0.0100 (11) | 0.0050 (10) | 0.0033 (8) | 0.0004 (8) | 0.0034 (9) |
O6 | 0.0072 (10) | 0.0079 (10) | 0.0053 (10) | 0.0042 (8) | 0.0004 (8) | 0.0008 (8) |
O7 | 0.0073 (10) | 0.0034 (9) | 0.0047 (10) | 0.0009 (8) | 0.0007 (8) | 0.0003 (8) |
O8 | 0.0086 (10) | 0.0052 (10) | 0.0115 (12) | 0.0014 (8) | 0.0041 (9) | 0.0054 (9) |
O9 | 0.0089 (10) | 0.0076 (10) | 0.0066 (11) | 0.0027 (8) | 0.0017 (9) | 0.0025 (8) |
B1 | 0.0067 (14) | 0.0041 (14) | 0.0056 (15) | 0.0024 (12) | 0.0006 (12) | 0.0024 (12) |
B2 | 0.0058 (14) | 0.0052 (15) | 0.0064 (15) | 0.0020 (12) | 0.0006 (12) | 0.0029 (12) |
B3 | 0.0097 (15) | 0.0046 (14) | 0.0035 (15) | 0.0020 (12) | 0.0012 (12) | 0.0011 (11) |
B4 | 0.0058 (14) | 0.0054 (15) | 0.0071 (16) | 0.0000 (12) | 0.0025 (12) | 0.0010 (12) |
Gd1—O7i | 2.334 (2) | B2—O8 | 1.485 (4) |
Gd1—O4ii | 2.366 (2) | B3—O4 | 1.458 (4) |
Gd1—O2iii | 2.383 (2) | B3—O6 | 1.467 (4) |
Gd1—O4 | 2.395 (2) | B3—O2 | 1.475 (4) |
Gd1—O9iv | 2.432 (2) | B3—O3 | 1.564 (4) |
Gd1—O3ii | 2.556 (2) | B4—O9 | 1.370 (4) |
Gd1—O9 | 2.602 (2) | B4—O8 | 1.371 (4) |
Gd1—O6iii | 2.656 (2) | B4—O5 | 1.389 (4) |
Gd1—O5ii | 2.688 (2) | O1—B1viii | 1.518 (4) |
Gd1—B3ii | 3.082 (3) | O1—Gd2ix | 2.433 (2) |
Gd1—B1i | 3.107 (4) | O1—Gd2iii | 2.568 (2) |
Gd1—Gd2 | 3.8082 (7) | O2—Gd2v | 2.376 (2) |
Gd2—O2 | 2.293 (2) | O2—Gd1iii | 2.383 (2) |
Gd2—O2v | 2.376 (2) | O3—Gd1ii | 2.556 (2) |
Gd2—O1vi | 2.433 (2) | O3—Gd2v | 2.559 (2) |
Gd2—O4 | 2.453 (2) | O4—Gd1ii | 2.366 (2) |
Gd2—O9ii | 2.475 (2) | O5—Gd2ii | 2.560 (2) |
Gd2—O8iii | 2.526 (2) | O5—Gd1ii | 2.688 (2) |
Gd2—O3v | 2.559 (2) | O6—Gd2iii | 2.631 (2) |
Gd2—O5ii | 2.560 (2) | O6—Gd1iii | 2.656 (2) |
Gd2—O1iii | 2.568 (2) | O7—Gd1x | 2.334 (2) |
Gd2—O6iii | 2.631 (2) | O8—Gd2iii | 2.526 (2) |
Gd2—B2iii | 2.782 (3) | O9—Gd1iv | 2.432 (2) |
Gd2—B3 | 2.852 (4) | O9—Gd2ii | 2.475 (2) |
B1—O7 | 1.442 (4) | B1—Gd2v | 3.052 (4) |
B1—O3 | 1.456 (4) | B1—Gd1x | 3.107 (4) |
B1—O5vii | 1.503 (4) | B2—Gd2iii | 2.782 (3) |
B1—O1viii | 1.518 (4) | B3—Gd2v | 3.039 (4) |
B2—O7 | 1.417 (4) | B3—Gd1ii | 3.082 (3) |
B2—O6 | 1.452 (4) | B4—Gd2ii | 2.922 (3) |
B2—O1 | 1.469 (4) | ||
O7i—Gd1—O4ii | 116.19 (8) | O8iii—Gd2—B2iii | 32.04 (9) |
O7i—Gd1—O2iii | 98.89 (8) | O3v—Gd2—B2iii | 99.33 (9) |
O4ii—Gd1—O2iii | 144.65 (8) | O5ii—Gd2—B2iii | 76.02 (8) |
O7i—Gd1—O4 | 116.33 (8) | O1iii—Gd2—B2iii | 31.56 (8) |
O4ii—Gd1—O4 | 73.67 (8) | O6iii—Gd2—B2iii | 30.96 (9) |
O2iii—Gd1—O4 | 87.50 (7) | O2—Gd2—B3 | 30.94 (9) |
O7i—Gd1—O9iv | 85.55 (8) | O2v—Gd2—B3 | 82.42 (9) |
O4ii—Gd1—O9iv | 114.94 (8) | O1vi—Gd2—B3 | 163.14 (9) |
O2iii—Gd1—O9iv | 69.90 (7) | O4—Gd2—B3 | 30.74 (9) |
O4—Gd1—O9iv | 151.21 (7) | O9ii—Gd2—B3 | 91.05 (9) |
O7i—Gd1—O3ii | 71.97 (7) | O8iii—Gd2—B3 | 107.60 (9) |
O4ii—Gd1—O3ii | 57.59 (7) | O3v—Gd2—B3 | 116.47 (9) |
O2iii—Gd1—O3ii | 146.24 (7) | O5ii—Gd2—B3 | 103.38 (9) |
O4—Gd1—O3ii | 125.97 (7) | O1iii—Gd2—B3 | 127.40 (8) |
O9iv—Gd1—O3ii | 76.92 (7) | O6iii—Gd2—B3 | 74.60 (8) |
O7i—Gd1—O9 | 155.97 (7) | B2iii—Gd2—B3 | 103.82 (10) |
O4ii—Gd1—O9 | 71.46 (7) | B2—O1—B1viii | 121.7 (2) |
O2iii—Gd1—O9 | 78.23 (7) | B2—O1—Gd2ix | 135.0 (2) |
O4—Gd1—O9 | 87.53 (8) | B1viii—O1—Gd2ix | 98.47 (17) |
O9iv—Gd1—O9 | 70.97 (8) | B2—O1—Gd2iii | 82.25 (16) |
O3ii—Gd1—O9 | 97.01 (7) | B1viii—O1—Gd2iii | 101.22 (17) |
O7i—Gd1—O6iii | 65.98 (7) | Gd2ix—O1—Gd2iii | 110.79 (8) |
O4ii—Gd1—O6iii | 135.58 (7) | B3—O2—Gd2 | 95.95 (17) |
O2iii—Gd1—O6iii | 54.74 (7) | B3—O2—Gd2v | 101.62 (17) |
O4—Gd1—O6iii | 67.68 (7) | Gd2—O2—Gd2v | 107.07 (8) |
O9iv—Gd1—O6iii | 109.48 (7) | B3—O2—Gd1iii | 106.10 (17) |
O3ii—Gd1—O6iii | 136.53 (7) | Gd2—O2—Gd1iii | 133.44 (10) |
O9—Gd1—O6iii | 126.12 (7) | Gd2v—O2—Gd1iii | 107.81 (8) |
O7i—Gd1—O5ii | 53.90 (7) | B1—O3—B3 | 113.3 (2) |
O4ii—Gd1—O5ii | 76.67 (8) | B1—O3—Gd1ii | 131.26 (19) |
O2iii—Gd1—O5ii | 125.70 (7) | B3—O3—Gd1ii | 93.73 (16) |
O4—Gd1—O5ii | 71.29 (7) | B1—O3—Gd2v | 94.99 (17) |
O9iv—Gd1—O5ii | 136.46 (7) | B3—O3—Gd2v | 91.72 (17) |
O3ii—Gd1—O5ii | 75.88 (7) | Gd1ii—O3—Gd2v | 125.21 (9) |
O9—Gd1—O5ii | 145.66 (7) | B3—O4—Gd1ii | 104.94 (18) |
O6iii—Gd1—O5ii | 70.97 (7) | B3—O4—Gd1 | 139.20 (18) |
O7i—Gd1—B3ii | 94.95 (9) | Gd1ii—O4—Gd1 | 106.33 (8) |
O4ii—Gd1—B3ii | 27.19 (8) | B3—O4—Gd2 | 89.96 (18) |
O2iii—Gd1—B3ii | 160.85 (9) | Gd1ii—O4—Gd2 | 109.35 (9) |
O4—Gd1—B3ii | 98.18 (8) | Gd1—O4—Gd2 | 103.55 (9) |
O9iv—Gd1—B3ii | 98.23 (9) | B4—O5—B1vii | 143.9 (3) |
O3ii—Gd1—B3ii | 30.43 (8) | B4—O5—Gd2ii | 90.48 (17) |
O9—Gd1—B3ii | 83.74 (8) | B1vii—O5—Gd2ii | 102.07 (17) |
O6iii—Gd1—B3ii | 144.17 (8) | B4—O5—Gd1ii | 122.2 (2) |
O5ii—Gd1—B3ii | 73.32 (9) | B1vii—O5—Gd1ii | 91.18 (17) |
O7i—Gd1—B1i | 26.12 (8) | Gd2ii—O5—Gd1ii | 93.02 (7) |
O4ii—Gd1—B1i | 101.72 (8) | B2—O6—B3 | 121.1 (2) |
O2iii—Gd1—B1i | 108.73 (8) | B2—O6—Gd2iii | 80.28 (16) |
O4—Gd1—B1i | 92.04 (8) | B3—O6—Gd2iii | 141.51 (18) |
O9iv—Gd1—B1i | 111.61 (8) | B2—O6—Gd1iii | 131.07 (18) |
O3ii—Gd1—B1i | 77.62 (8) | B3—O6—Gd1iii | 94.40 (18) |
O9—Gd1—B1i | 173.01 (8) | Gd2iii—O6—Gd1iii | 92.16 (7) |
O6iii—Gd1—B1i | 59.79 (8) | B2—O7—B1 | 118.8 (3) |
O5ii—Gd1—B1i | 28.93 (7) | B2—O7—Gd1x | 127.3 (2) |
B3ii—Gd1—B1i | 89.43 (9) | B1—O7—Gd1x | 108.43 (18) |
O7i—Gd1—Gd2 | 77.64 (6) | B4—O8—B2 | 123.2 (2) |
O4ii—Gd1—Gd2 | 92.09 (6) | B4—O8—Gd2iii | 127.1 (2) |
O2iii—Gd1—Gd2 | 91.22 (6) | B2—O8—Gd2iii | 83.50 (16) |
O4—Gd1—Gd2 | 38.76 (6) | B4—O9—Gd1iv | 134.4 (2) |
O9iv—Gd1—Gd2 | 152.52 (6) | B4—O9—Gd2ii | 94.54 (18) |
O3ii—Gd1—Gd2 | 117.11 (5) | Gd1iv—O9—Gd2ii | 103.22 (9) |
O9—Gd1—Gd2 | 125.99 (5) | B4—O9—Gd1 | 108.0 (2) |
O6iii—Gd1—Gd2 | 43.65 (5) | Gd1iv—O9—Gd1 | 109.03 (8) |
O5ii—Gd1—Gd2 | 42.16 (5) | Gd2ii—O9—Gd1 | 101.44 (8) |
B3ii—Gd1—Gd2 | 104.68 (7) | O7—B1—O3 | 111.6 (3) |
B1i—Gd1—Gd2 | 54.52 (6) | O7—B1—O5vii | 102.5 (3) |
O2—Gd2—O2v | 72.93 (8) | O3—B1—O5vii | 122.9 (2) |
O2—Gd2—O1vi | 142.28 (8) | O7—B1—O1viii | 114.1 (2) |
O2v—Gd2—O1vi | 80.93 (8) | O3—B1—O1viii | 104.1 (3) |
O2—Gd2—O4 | 61.45 (7) | O5vii—B1—O1viii | 101.5 (2) |
O2v—Gd2—O4 | 98.14 (8) | O7—B1—Gd2v | 147.8 (2) |
O1vi—Gd2—O4 | 151.13 (7) | O3—B1—Gd2v | 56.63 (15) |
O2—Gd2—O9ii | 113.51 (8) | O5vii—B1—Gd2v | 108.67 (19) |
O2v—Gd2—O9ii | 69.26 (7) | O1viii—B1—Gd2v | 52.05 (14) |
O1vi—Gd2—O9ii | 80.57 (8) | O7—B1—Gd1x | 45.45 (14) |
O4—Gd2—O9ii | 72.32 (7) | O3—B1—Gd1x | 148.3 (2) |
O2—Gd2—O8iii | 89.03 (8) | O5vii—B1—Gd1x | 59.88 (15) |
O2v—Gd2—O8iii | 125.54 (7) | O1viii—B1—Gd1x | 105.96 (18) |
O1vi—Gd2—O8iii | 84.45 (8) | Gd2v—B1—Gd1x | 154.99 (12) |
O4—Gd2—O8iii | 117.67 (8) | O7—B2—O6 | 113.5 (3) |
O9ii—Gd2—O8iii | 156.87 (7) | O7—B2—O1 | 112.7 (3) |
O2—Gd2—O3v | 87.00 (7) | O6—B2—O1 | 108.5 (3) |
O2v—Gd2—O3v | 59.28 (7) | O7—B2—O8 | 114.2 (3) |
O1vi—Gd2—O3v | 55.99 (7) | O6—B2—O8 | 106.0 (2) |
O4—Gd2—O3v | 146.52 (7) | O1—B2—O8 | 101.0 (2) |
O9ii—Gd2—O3v | 115.18 (7) | O7—B2—Gd2iii | 177.7 (2) |
O8iii—Gd2—O3v | 69.08 (7) | O6—B2—Gd2iii | 68.76 (15) |
O2—Gd2—O5ii | 133.37 (8) | O1—B2—Gd2iii | 66.19 (15) |
O2v—Gd2—O5ii | 124.07 (7) | O8—B2—Gd2iii | 64.46 (15) |
O1vi—Gd2—O5ii | 83.90 (7) | O4—B3—O6 | 117.6 (3) |
O4—Gd2—O5ii | 72.69 (7) | O4—B3—O2 | 111.8 (3) |
O9ii—Gd2—O5ii | 55.22 (7) | O6—B3—O2 | 104.7 (2) |
O8iii—Gd2—O5ii | 105.85 (7) | O4—B3—O3 | 103.6 (2) |
O3v—Gd2—O5ii | 139.63 (7) | O6—B3—O3 | 111.6 (3) |
O2—Gd2—O1iii | 132.56 (7) | O2—B3—O3 | 107.2 (2) |
O2v—Gd2—O1iii | 150.15 (7) | O4—B3—Gd2 | 59.30 (15) |
O1vi—Gd2—O1iii | 69.21 (8) | O6—B3—Gd2 | 136.1 (2) |
O4—Gd2—O1iii | 107.92 (7) | O2—B3—Gd2 | 53.10 (14) |
O9ii—Gd2—O1iii | 104.67 (7) | O3—B3—Gd2 | 111.32 (19) |
O8iii—Gd2—O1iii | 53.16 (7) | O4—B3—Gd2v | 124.7 (2) |
O3v—Gd2—O1iii | 101.61 (7) | O6—B3—Gd2v | 117.68 (19) |
O5ii—Gd2—O1iii | 54.31 (7) | O2—B3—Gd2v | 50.00 (13) |
O2—Gd2—O6iii | 81.43 (7) | O3—B3—Gd2v | 57.32 (14) |
O2v—Gd2—O6iii | 154.31 (7) | Gd2—B3—Gd2v | 79.16 (9) |
O1vi—Gd2—O6iii | 122.24 (7) | O4—B3—Gd1ii | 47.87 (14) |
O4—Gd2—O6iii | 67.32 (7) | O6—B3—Gd1ii | 130.1 (2) |
O9ii—Gd2—O6iii | 121.69 (7) | O2—B3—Gd1ii | 125.09 (19) |
O8iii—Gd2—O6iii | 54.06 (7) | O3—B3—Gd1ii | 55.85 (13) |
O3v—Gd2—O6iii | 121.88 (7) | Gd2—B3—Gd1ii | 82.88 (9) |
O5ii—Gd2—O6iii | 73.40 (7) | Gd2v—B3—Gd1ii | 95.79 (9) |
O1iii—Gd2—O6iii | 54.25 (7) | O9—B4—O8 | 121.3 (3) |
O2—Gd2—B2iii | 101.20 (9) | O9—B4—O5 | 115.6 (3) |
O2v—Gd2—B2iii | 157.57 (9) | O8—B4—O5 | 122.7 (3) |
O1vi—Gd2—B2iii | 92.64 (9) | O9—B4—Gd2ii | 57.60 (15) |
O4—Gd2—B2iii | 97.69 (9) | O8—B4—Gd2ii | 168.1 (2) |
O9ii—Gd2—B2iii | 131.15 (9) | O5—B4—Gd2ii | 61.15 (15) |
Symmetry codes: (i) x, y, z−1; (ii) −x+2, −y+1, −z+1; (iii) −x+1, −y+1, −z+1; (iv) −x+2, −y+2, −z+1; (v) −x+1, −y, −z+1; (vi) x, y−1, z−1; (vii) −x+2, −y+1, −z+2; (viii) −x+1, −y+1, −z+2; (ix) x, y+1, z+1; (x) x, y, z+1. |
Experimental details
Crystal data | |
Chemical formula | Gd2B4O9 |
Mr | 501.74 |
Crystal system, space group | Triclinic, P1 |
Temperature (K) | 293 |
a, b, c (Å) | 6.1973 (10), 6.4757 (10), 7.5249 (10) |
α, β, γ (°) | 102.386 (10), 96.983 (10), 102.544 (10) |
V (Å3) | 283.41 (8) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 23.23 |
Crystal size (mm) | 0.05 × 0.04 × 0.02 |
Data collection | |
Diffractometer | Nonius KappaCCD area-detector diffractometer |
Absorption correction | Numerical (HABITUS; Herrendorf & Bärnighausen, 1997) |
Tmin, Tmax | 0.365, 0.695 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 10001, 3007, 2538 |
Rint | 0.045 |
(sin θ/λ)max (Å−1) | 0.864 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.026, 0.050, 1.00 |
No. of reflections | 3007 |
No. of parameters | 137 |
Δρmax, Δρmin (e Å−3) | 2.30, −2.93 |
Computer programs: COLLECT (Nonius, 1997-2000), HKL SCALEPACK (Otwinowski & Minor, 1997), HKL DENZO (Otwinowski & Minor, 1997) and SCALEPACK, SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), DIAMOND (Brandenburg & Berndt, 1999), enCIFer (Allen et al., 2004) and SHELXL97.
Gd1—O7i | 2.334 (2) | Gd2—O1iii | 2.568 (2) |
Gd1—O4ii | 2.366 (2) | Gd2—O6iii | 2.631 (2) |
Gd1—O2iii | 2.383 (2) | B1—O7 | 1.442 (4) |
Gd1—O4 | 2.395 (2) | B1—O3 | 1.456 (4) |
Gd1—O9iv | 2.432 (2) | B1—O5vii | 1.503 (4) |
Gd1—O3ii | 2.556 (2) | B1—O1viii | 1.518 (4) |
Gd1—O9 | 2.602 (2) | B2—O7 | 1.417 (4) |
Gd1—O6iii | 2.656 (2) | B2—O6 | 1.452 (4) |
Gd1—O5ii | 2.688 (2) | B2—O1 | 1.469 (4) |
Gd2—O2 | 2.293 (2) | B2—O8 | 1.485 (4) |
Gd2—O2v | 2.376 (2) | B3—O4 | 1.458 (4) |
Gd2—O1vi | 2.433 (2) | B3—O6 | 1.467 (4) |
Gd2—O4 | 2.453 (2) | B3—O2 | 1.475 (4) |
Gd2—O9ii | 2.475 (2) | B3—O3 | 1.564 (4) |
Gd2—O8iii | 2.526 (2) | B4—O9 | 1.370 (4) |
Gd2—O3v | 2.559 (2) | B4—O8 | 1.371 (4) |
Gd2—O5ii | 2.560 (2) | B4—O5 | 1.389 (4) |
Symmetry codes: (i) x, y, z−1; (ii) −x+2, −y+1, −z+1; (iii) −x+1, −y+1, −z+1; (iv) −x+2, −y+2, −z+1; (v) −x+1, −y, −z+1; (vi) x, y−1, z−1; (vii) −x+2, −y+1, −z+2; (viii) −x+1, −y+1, −z+2. |
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High-pressure multi-anvil techniques have made it possible to extend substantially the structural and compositional diversity in oxoborate chemistry. Recently, we reported the syntheses and crystal structures of the new rare-earth oxoborates α-RE2B4O9, with RE = Sm and Ho, displaying the new structural motif of edge-sharing BO4 tetrahedra (Emme & Huppertz, 2005). These structures are isotypic with the compounds α-RE2B4O9 (RE = Eu—Dy) synthesized by Emme & Huppertz (2002, 2003). They represent the first examples of 1:2 compounds in the RE2O3—B2O3 system. Huppertz et al. (2003) synthesized a new polymorph, β-Dy2B4O9, exhibiting a new structure type built up from triangular BO3 and tetrahedral BO4 groups. This synthesis was carried out under extreme high-pressure/high-temperature conditions of 8 GPa and 1273 K using Dy2O3 and boron oxide in a B2O3/Na2O2 flux. At pressures of 8 GPa, borate structures built up exclusively of BO4 tetrahedra are normally expected. The appearance of triangular BO3 groups besides tetrahedral BO4 groups in β-Dy2B4O9 implied that the flux supports the formation of a structure which is normally expected at lower pressures. Systematic investigations of the 1 RE2O3: 2 B2O3 system confirmed this suspicion. Ongoing experiments have shown that it is possible to synthesize β-Dy2B4O9 in the lower-pressure range of 4–6.3 GPa at 1223 K directly, starting with pure B2O3 and Dy2O3. Analogous experiments with Gd2O3 led to the isotypic gadolinium compound in the pressure range 3–5 GPa and 1223 K. A detailed study concerning the formation ranges showed that, at lower pressures, the triclinic phases ν-REBO3 (RE = Gd or Dy) were formed (Emme & Huppertz, 2004). The normal-pressure phases π-REBO3 occur below 2 GPa for RE = Gd and below 3 GPa for RE = Dy. Above 5 GPa (RE = Gd) and 6.3 GPa (RE = Dy), the experiments resulted in the formation of the α phases.
The crystal structure of β-Gd2B4O9 is built up of triangular BO3 groups and BO4 tetrahedra forming [100] ribbons (Fig. 1), with the Gd3+ cations positioned in the voids between the ribbons. The bond-valence sums for the two crystallograpically independent Gd3+ cations are 3.02 for Gd1 and 3.31 for Gd2 (Brese & O'Keeffe, 1991). Within the ribbons, the BO4 tetrahedra form three-membered B3O9 rings linked to each other via two triangular BO3 groups, forming six-membered rings (Fig. 2). Additionally, each B3O9 ring is connected to the adjacent ring via two common corners, forming four-membered rings.