Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270107054078/fa3116sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270107054078/fa3116Isup2.hkl |
A mixture of analytically pure Rb2CO3 (3.80 g, 0.0165 mol), Y2O3 (0.60 g, 0.00266 mol) and H3BO3 (1.20 g, 0.01941 mol) was transferred to an Au crucible. The sample was melted at 1200 K for one day, cooled to 950 K at a rate of 5 K h-1, and then cooled to room temperature in the furnace with power off. Colorless crystals were recovered by washing the content of the crucible with hot water.
Direct phase determination showed the positions of five heavy atoms, which were assigned to three Y and two Rb atoms. Subsequent difference Fourier syntheses revealed the positions of the O atoms. Judging from the distances of heavy atoms to oxygen, the heavy atoms were then assigned as three Rb and two Y atoms. The final difference electron-density map shows a high peak located 0.14 Å from atom Rb3 and a deepest hole located 0.78 Å from atom Y2. The final result was tested using PLATON (Spek, 2003), and no additional symmetry was found. The centrosymmetric space group Pnma was also proposed by XPREP (Sheldrick, 1997); however, structure solution could not proceed further after the Y and Rb atoms were found.
Data collection: CrystalClear (Rigaku, 2005); cell refinement: CrystalClear (Rigaku, 2005); data reduction: CrystalClear (Rigaku, 2005); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and Balls & Sticks (Sung & Ozawa, 2004); software used to prepare material for publication: publCIF (Westrip, 2007).
Rb3Y2(BO3)3 | F(000) = 1104 |
Mr = 610.66 | Dx = 4.008 Mg m−3 |
Orthorhombic, Pna21 | Mo Kα radiation, λ = 0.71070 Å |
Hall symbol: P 2c -2n | Cell parameters from 2576 reflections |
a = 8.6811 (4) Å | θ = 2.1–28.7° |
b = 9.5627 (4) Å | µ = 25.77 mm−1 |
c = 12.1914 (6) Å | T = 113 K |
V = 1012.07 (8) Å3 | Prism, colorless |
Z = 4 | 0.24 × 0.21 × 0.20 mm |
Rigaku Saturn diffractometer | 2602 independent reflections |
Radiation source: rotating anode | 2338 reflections with I > 2σ(I) |
Confocal monochromator | Rint = 0.113 |
Detector resolution: 7.31 pixels mm-1 | θmax = 28.7°, θmin = 2.7° |
ω scans | h = −11→11 |
Absorption correction: numerical (NUMABS; Rigaku, 2005) | k = −12→12 |
Tmin = 0.063, Tmax = 0.079 | l = −16→16 |
12567 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)] = 0.048 | w = 1/[σ2(Fo2) + (0.013P)2] where P = (Fo2 + 2Fc2)/3 |
wR(F2) = 0.079 | (Δ/σ)max < 0.001 |
S = 1.00 | Δρmax = 1.47 e Å−3 |
2602 reflections | Δρmin = −1.14 e Å−3 |
155 parameters | Absolute structure: Flack (1983), 1238 Friedel pairs |
7 restraints | Absolute structure parameter: 0.013 (15) |
Rb3Y2(BO3)3 | V = 1012.07 (8) Å3 |
Mr = 610.66 | Z = 4 |
Orthorhombic, Pna21 | Mo Kα radiation |
a = 8.6811 (4) Å | µ = 25.77 mm−1 |
b = 9.5627 (4) Å | T = 113 K |
c = 12.1914 (6) Å | 0.24 × 0.21 × 0.20 mm |
Rigaku Saturn diffractometer | 2602 independent reflections |
Absorption correction: numerical (NUMABS; Rigaku, 2005) | 2338 reflections with I > 2σ(I) |
Tmin = 0.063, Tmax = 0.079 | Rint = 0.113 |
12567 measured reflections |
R[F2 > 2σ(F2)] = 0.048 | 7 restraints |
wR(F2) = 0.079 | Δρmax = 1.47 e Å−3 |
S = 1.00 | Δρmin = −1.14 e Å−3 |
2602 reflections | Absolute structure: Flack (1983), 1238 Friedel pairs |
155 parameters | Absolute structure parameter: 0.013 (15) |
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 | ||
Rb1 | 0.09493 (9) | 0.69553 (8) | 0.59244 (8) | 0.0145 (2) | |
Rb2 | −0.29558 (9) | 0.46888 (8) | 0.57953 (9) | 0.0174 (2) | |
Rb3 | 0.35348 (11) | 0.35789 (9) | 0.74228 (8) | 0.0137 (2) | |
Y1 | 0.00906 (12) | 0.50802 (10) | 0.33006 (9) | 0.0117 (2) | |
Y2 | 0.35696 (10) | 0.38659 (9) | 0.39782 (7) | 0.0115 (2) | |
O1 | 0.3796 (7) | 0.8201 (6) | 0.4106 (5) | 0.0126 (14) | |
O2 | 0.4540 (6) | 0.5876 (6) | 0.4675 (5) | 0.0148 (14) | |
O3 | 0.2511 (7) | 0.6105 (6) | 0.3409 (5) | 0.0150 (14) | |
O4 | 0.1737 (7) | 0.3367 (6) | 0.2601 (5) | 0.0118 (14) | |
O5 | 0.0374 (7) | 0.1205 (6) | 0.2707 (5) | 0.0144 (15) | |
O6 | 0.3036 (7) | 0.1420 (5) | 0.3343 (5) | 0.0126 (13) | |
O7 | 0.1200 (6) | 0.4176 (6) | 0.4852 (5) | 0.0128 (14) | |
O8 | −0.0371 (6) | 0.2269 (5) | 0.5377 (4) | 0.0127 (13) | |
O9 | 0.0244 (6) | 0.4039 (6) | 0.6678 (5) | 0.0124 (13) | |
B1 | 0.3637 (12) | 0.6741 (11) | 0.4076 (10) | 0.014 (2) | |
B2 | 0.1695 (13) | 0.1962 (11) | 0.2872 (9) | 0.014 (2) | |
B3 | 0.0371 (10) | 0.3487 (10) | 0.5645 (9) | 0.013 (2) |
U11 | U22 | U33 | U12 | U13 | U23 | |
Rb1 | 0.0192 (5) | 0.0133 (4) | 0.0111 (4) | −0.0009 (3) | −0.0020 (4) | 0.0005 (4) |
Rb2 | 0.0166 (4) | 0.0150 (4) | 0.0206 (5) | 0.0011 (3) | −0.0042 (5) | −0.0009 (5) |
Rb3 | 0.0161 (5) | 0.0127 (4) | 0.0123 (5) | −0.0004 (4) | 0.0013 (4) | −0.0003 (4) |
Y1 | 0.0148 (4) | 0.0114 (4) | 0.0088 (4) | 0.0001 (3) | 0.0000 (3) | 0.0001 (3) |
Y2 | 0.0142 (5) | 0.0117 (4) | 0.0085 (4) | 0.0001 (3) | 0.0000 (4) | 0.0003 (4) |
O1 | 0.018 (4) | 0.011 (3) | 0.008 (3) | −0.001 (3) | 0.002 (3) | 0.000 (3) |
O2 | 0.020 (4) | 0.009 (3) | 0.016 (3) | −0.002 (3) | −0.011 (3) | 0.000 (3) |
O3 | 0.020 (4) | 0.013 (3) | 0.012 (4) | −0.002 (3) | 0.001 (3) | 0.001 (3) |
O4 | 0.019 (4) | 0.012 (3) | 0.004 (3) | −0.003 (3) | 0.001 (3) | −0.002 (2) |
O5 | 0.019 (4) | 0.011 (3) | 0.014 (3) | 0.001 (3) | 0.007 (3) | −0.002 (3) |
O6 | 0.014 (3) | 0.011 (3) | 0.012 (3) | 0.001 (3) | 0.000 (3) | 0.000 (3) |
O7 | 0.015 (3) | 0.013 (3) | 0.010 (3) | −0.004 (3) | 0.000 (3) | 0.003 (3) |
O8 | 0.012 (3) | 0.018 (3) | 0.009 (3) | −0.005 (3) | 0.004 (2) | −0.006 (3) |
O9 | 0.014 (3) | 0.015 (3) | 0.009 (3) | −0.004 (3) | 0.002 (3) | 0.001 (3) |
B1 | 0.012 (6) | 0.015 (5) | 0.015 (6) | 0.000 (4) | 0.002 (5) | −0.004 (5) |
B2 | 0.015 (4) | 0.019 (4) | 0.008 (4) | −0.001 (3) | 0.007 (3) | −0.003 (3) |
B3 | 0.010 (5) | 0.012 (5) | 0.017 (6) | 0.000 (4) | 0.001 (5) | 0.001 (4) |
Rb1—O2i | 2.849 (5) | Rb3—O6iii | 3.240 (5) |
Rb1—O1i | 2.904 (6) | Rb3—O2viii | 3.257 (6) |
Rb1—O7 | 2.970 (6) | Y1—O9ix | 2.169 (6) |
Rb1—O9 | 2.999 (6) | Y1—O1i | 2.220 (6) |
Rb1—O5ii | 3.023 (6) | Y1—O6v | 2.290 (6) |
Rb1—O4ii | 3.116 (6) | Y1—O7 | 2.292 (6) |
Rb1—O6iii | 3.119 (7) | Y1—O3 | 2.323 (6) |
Rb1—B2iii | 3.134 (11) | Y1—O4 | 2.336 (6) |
Rb1—O4iii | 3.167 (6) | Y2—O5vi | 2.204 (6) |
Rb2—O2iv | 2.807 (5) | Y2—O8vi | 2.221 (5) |
Rb2—O8v | 2.857 (5) | Y2—O2 | 2.264 (5) |
Rb2—O9 | 3.043 (6) | Y2—O7 | 2.335 (5) |
Rb2—O4ii | 3.069 (6) | Y2—O4 | 2.362 (6) |
Rb2—B3 | 3.114 (9) | Y2—O3 | 2.431 (6) |
Rb2—O1i | 3.260 (6) | Y2—O6 | 2.507 (5) |
Rb2—O8 | 3.263 (5) | O1—B1 | 1.404 (12) |
Rb2—O6v | 3.287 (7) | O2—B1 | 1.354 (12) |
Rb2—O3ii | 3.299 (6) | O3—B1 | 1.408 (12) |
Rb3—O5iii | 2.706 (6) | O4—B2 | 1.384 (12) |
Rb3—O8vi | 2.790 (5) | O5—B2 | 1.371 (12) |
Rb3—O3vii | 2.805 (6) | O6—B2 | 1.397 (12) |
Rb3—O1vii | 2.904 (6) | O7—B3 | 1.374 (11) |
Rb3—O9 | 3.030 (6) | O8—B3 | 1.370 (10) |
Rb3—O9vi | 3.048 (6) | O9—B3 | 1.370 (12) |
Rb3—B1viii | 3.191 (11) | ||
O2i—Rb1—O1i | 49.68 (16) | O5iii—Rb3—O8vi | 105.38 (17) |
O2i—Rb1—O7 | 116.58 (16) | O5iii—Rb3—O3vii | 147.24 (18) |
O1i—Rb1—O7 | 70.42 (16) | O8vi—Rb3—O3vii | 104.39 (16) |
O2i—Rb1—O9 | 138.84 (15) | O5iii—Rb3—O1vii | 105.59 (18) |
O1i—Rb1—O9 | 93.13 (17) | O8vi—Rb3—O1vii | 146.38 (16) |
O7—Rb1—O9 | 46.99 (15) | O3vii—Rb3—O1vii | 50.70 (16) |
O2i—Rb1—O5ii | 78.31 (18) | O5iii—Rb3—O9 | 103.52 (17) |
O1i—Rb1—O5ii | 109.53 (15) | O8vi—Rb3—O9 | 95.47 (16) |
O7—Rb1—O5ii | 149.90 (16) | O3vii—Rb3—O9 | 86.88 (16) |
O9—Rb1—O5ii | 104.08 (16) | O1vii—Rb3—O9 | 64.71 (17) |
O2i—Rb1—O4ii | 95.79 (17) | O5iii—Rb3—O9vi | 129.04 (17) |
O1i—Rb1—O4ii | 90.79 (14) | O8vi—Rb3—O9vi | 47.88 (15) |
O7—Rb1—O4ii | 104.78 (16) | O3vii—Rb3—O9vi | 65.96 (16) |
O9—Rb1—O4ii | 63.54 (16) | O1vii—Rb3—O9vi | 116.57 (16) |
O5ii—Rb1—O4ii | 45.70 (16) | O9—Rb3—O9vi | 119.27 (16) |
O2i—Rb1—O6iii | 138.23 (16) | O5iii—Rb3—O6iii | 47.53 (17) |
O1i—Rb1—O6iii | 153.51 (16) | O8vi—Rb3—O6iii | 134.15 (16) |
O7—Rb1—O6iii | 104.40 (15) | O3vii—Rb3—O6iii | 115.00 (18) |
O9—Rb1—O6iii | 67.40 (15) | O1vii—Rb3—O6iii | 64.32 (15) |
O5ii—Rb1—O6iii | 61.52 (15) | O9—Rb3—O6iii | 65.49 (16) |
O4ii—Rb1—O6iii | 64.87 (15) | O9vi—Rb3—O6iii | 175.21 (16) |
O2i—Rb1—B2iii | 133.1 (2) | B1viii—Rb3—O6iii | 100.7 (2) |
O1i—Rb1—B2iii | 177.1 (2) | O5iii—Rb3—O2viii | 64.14 (15) |
O7—Rb1—B2iii | 106.7 (2) | O8vi—Rb3—O2viii | 128.74 (14) |
O9—Rb1—B2iii | 84.4 (2) | O3vii—Rb3—O2viii | 86.54 (16) |
O5ii—Rb1—B2iii | 72.7 (2) | O1vii—Rb3—O2viii | 77.39 (15) |
O4ii—Rb1—B2iii | 89.5 (2) | O9—Rb3—O2viii | 135.51 (15) |
O6iii—Rb1—B2iii | 25.8 (2) | O9vi—Rb3—O2viii | 97.63 (15) |
O2i—Rb1—O4iii | 107.88 (16) | B1viii—Rb3—O2viii | 24.2 (2) |
O1i—Rb1—O4iii | 157.34 (18) | O6iii—Rb3—O2viii | 77.87 (15) |
O7—Rb1—O4iii | 128.24 (15) | O9ix—Y1—O1i | 92.7 (2) |
O9—Rb1—O4iii | 109.15 (16) | O9ix—Y1—O6v | 99.2 (2) |
O5ii—Rb1—O4iii | 61.90 (15) | O1i—Y1—O6v | 93.4 (2) |
O4ii—Rb1—O4iii | 95.37 (17) | O9ix—Y1—O7 | 162.78 (19) |
O6iii—Rb1—O4iii | 44.02 (15) | O1i—Y1—O7 | 97.3 (2) |
O2iv—Rb2—O8v | 67.03 (15) | O6v—Y1—O7 | 94.1 (2) |
O2iv—Rb2—O9 | 164.07 (17) | O9ix—Y1—O3 | 90.5 (2) |
O8v—Rb2—O9 | 126.81 (16) | O1i—Y1—O3 | 96.9 (2) |
O2iv—Rb2—O4ii | 111.76 (16) | O6v—Y1—O3 | 165.5 (2) |
O8v—Rb2—O4ii | 141.08 (15) | O7—Y1—O3 | 74.5 (2) |
O9—Rb2—O4ii | 63.61 (16) | O9ix—Y1—O4 | 91.2 (2) |
O2iv—Rb2—O1i | 78.68 (17) | O1i—Y1—O4 | 172.2 (2) |
O8v—Rb2—O1i | 129.43 (16) | O6v—Y1—O4 | 92.6 (2) |
O9—Rb2—O1i | 85.65 (15) | O7—Y1—O4 | 77.3 (2) |
O4ii—Rb2—O1i | 85.26 (14) | O3—Y1—O4 | 76.3 (2) |
B3—Rb2—O1i | 76.0 (2) | O5vi—Y2—O8vi | 103.3 (2) |
O2iv—Rb2—O8 | 138.01 (16) | O5vi—Y2—O2 | 91.5 (2) |
O8v—Rb2—O8 | 90.69 (4) | O8vi—Y2—O2 | 88.4 (2) |
O9—Rb2—O8 | 44.18 (14) | O5vi—Y2—O7 | 161.9 (2) |
O4ii—Rb2—O8 | 107.74 (15) | O8vi—Y2—O7 | 94.40 (19) |
B3—Rb2—O8 | 24.67 (18) | O2—Y2—O7 | 92.8 (2) |
O1i—Rb2—O8 | 91.11 (14) | O5vi—Y2—O4 | 88.4 (2) |
O2iv—Rb2—O6v | 83.74 (16) | O8vi—Y2—O4 | 136.6 (2) |
O8v—Rb2—O6v | 79.53 (14) | O2—Y2—O4 | 133.6 (2) |
O9—Rb2—O6v | 90.97 (15) | O7—Y2—O4 | 75.9 (2) |
O4ii—Rb2—O6v | 139.25 (14) | O5vi—Y2—O3 | 95.5 (2) |
B3—Rb2—O6v | 65.5 (2) | O8vi—Y2—O3 | 143.7 (2) |
O1i—Rb2—O6v | 60.19 (14) | O2—Y2—O3 | 60.0 (2) |
O8—Rb2—O6v | 56.56 (13) | O7—Y2—O3 | 71.7 (2) |
O2iv—Rb2—O3ii | 130.81 (17) | O4—Y2—O3 | 73.8 (2) |
O8v—Rb2—O3ii | 96.17 (15) | O5vi—Y2—O6 | 83.4 (2) |
O9—Rb2—O3ii | 60.30 (15) | O8vi—Y2—O6 | 81.8 (2) |
O4ii—Rb2—O3ii | 53.58 (15) | O2—Y2—O6 | 167.63 (19) |
B3—Rb2—O3ii | 82.1 (2) | O7—Y2—O6 | 95.5 (2) |
O1i—Rb2—O3ii | 134.30 (15) | O4—Y2—O6 | 57.8 (2) |
O8—Rb2—O3ii | 84.69 (14) | O3—Y2—O6 | 131.6 (2) |
O6v—Rb2—O3ii | 140.70 (14) | O2—B1—O1 | 122.5 (9) |
O2iv—Rb2—O5x | 71.81 (16) | O2—B1—O3 | 116.7 (8) |
O8v—Rb2—O5x | 87.11 (14) | O1—B1—O3 | 120.8 (9) |
O9—Rb2—O5x | 113.67 (15) | O5—B2—O4 | 120.0 (9) |
O4ii—Rb2—O5x | 58.09 (15) | O5—B2—O6 | 124.1 (9) |
B3—Rb2—O5x | 139.3 (2) | O4—B2—O6 | 115.8 (9) |
O1i—Rb2—O5x | 116.74 (14) | O8—B3—O9 | 120.6 (8) |
O8—Rb2—O5x | 145.15 (14) | O8—B3—O7 | 119.1 (9) |
O6v—Rb2—O5x | 155.23 (14) | O9—B3—O7 | 120.3 (8) |
O3ii—Rb2—O5x | 61.05 (14) |
Symmetry codes: (i) x−1/2, −y+3/2, z; (ii) −x, −y+1, z+1/2; (iii) −x+1/2, y+1/2, z+1/2; (iv) x−1, y, z; (v) x−1/2, −y+1/2, z; (vi) x+1/2, −y+1/2, z; (vii) −x+1/2, y−1/2, z+1/2; (viii) −x+1, −y+1, z+1/2; (ix) −x, −y+1, z−1/2; (x) −x−1/2, y+1/2, z+1/2. |
Experimental details
Crystal data | |
Chemical formula | Rb3Y2(BO3)3 |
Mr | 610.66 |
Crystal system, space group | Orthorhombic, Pna21 |
Temperature (K) | 113 |
a, b, c (Å) | 8.6811 (4), 9.5627 (4), 12.1914 (6) |
V (Å3) | 1012.07 (8) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 25.77 |
Crystal size (mm) | 0.24 × 0.21 × 0.20 |
Data collection | |
Diffractometer | Rigaku Saturn diffractometer |
Absorption correction | Numerical (NUMABS; Rigaku, 2005) |
Tmin, Tmax | 0.063, 0.079 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 12567, 2602, 2338 |
Rint | 0.113 |
(sin θ/λ)max (Å−1) | 0.675 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.048, 0.079, 1.00 |
No. of reflections | 2602 |
No. of parameters | 155 |
No. of restraints | 7 |
Δρmax, Δρmin (e Å−3) | 1.47, −1.14 |
Absolute structure | Flack (1983), 1238 Friedel pairs |
Absolute structure parameter | 0.013 (15) |
Computer programs: CrystalClear (Rigaku, 2005), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), ORTEP-3 for Windows (Farrugia, 1997) and Balls & Sticks (Sung & Ozawa, 2004), publCIF (Westrip, 2007).
Rb1—O2i | 2.849 (5) | Y1—O7 | 2.292 (6) |
Rb1—O1i | 2.904 (6) | Y1—O3 | 2.323 (6) |
Rb1—O7 | 2.970 (6) | Y1—O4 | 2.336 (6) |
Rb1—O9 | 2.999 (6) | Y2—O5vi | 2.204 (6) |
Rb1—O5ii | 3.023 (6) | Y2—O8vi | 2.221 (5) |
Rb1—O4ii | 3.116 (6) | Y2—O2 | 2.264 (5) |
Rb1—O6iii | 3.119 (7) | Y2—O7 | 2.335 (5) |
Rb2—O2iv | 2.807 (5) | Y2—O4 | 2.362 (6) |
Rb2—O8v | 2.857 (5) | Y2—O3 | 2.431 (6) |
Rb2—O9 | 3.043 (6) | Y2—O6 | 2.507 (5) |
Rb2—O4ii | 3.069 (6) | O1—B1 | 1.404 (12) |
Rb3—O5iii | 2.706 (6) | O2—B1 | 1.354 (12) |
Rb3—O8vi | 2.790 (5) | O3—B1 | 1.408 (12) |
Rb3—O3vii | 2.805 (6) | O4—B2 | 1.384 (12) |
Rb3—O1vii | 2.904 (6) | O5—B2 | 1.371 (12) |
Rb3—O9 | 3.030 (6) | O6—B2 | 1.397 (12) |
Rb3—O9vi | 3.048 (6) | O7—B3 | 1.374 (11) |
Y1—O9viii | 2.169 (6) | O8—B3 | 1.370 (10) |
Y1—O1i | 2.220 (6) | O9—B3 | 1.370 (12) |
Y1—O6v | 2.290 (6) | ||
O2—B1—O1 | 122.5 (9) | O4—B2—O6 | 115.8 (9) |
O2—B1—O3 | 116.7 (8) | O8—B3—O9 | 120.6 (8) |
O1—B1—O3 | 120.8 (9) | O8—B3—O7 | 119.1 (9) |
O5—B2—O4 | 120.0 (9) | O9—B3—O7 | 120.3 (8) |
O5—B2—O6 | 124.1 (9) |
Symmetry codes: (i) x−1/2, −y+3/2, z; (ii) −x, −y+1, z+1/2; (iii) −x+1/2, y+1/2, z+1/2; (iv) x−1, y, z; (v) x−1/2, −y+1/2, z; (vi) x+1/2, −y+1/2, z; (vii) −x+1/2, y−1/2, z+1/2; (viii) −x, −y+1, z−1/2. |
Though there are several Li- and Na-containing rare earth borate compounds, including Li6Y(BO3)3 (Tu et al., 1989), LiGd6O5(BO3)3 (Chaminade et al., 1999), Li3Nd2(BO3)3 (Abdullaev & Mamedov, 1977), Li2Yb5O4(BO3)3 (Jubera et al., 2001), Na3Nd(BO3)2 (Mascetti et al.,1981), Na3La2(BO3)3 (Zhang et al., 2001), Na2Gd2O(BO3)2 (Corbel & Leblanc, 1999) and Na3La9O3(BO3)8 (Gravereau et al., 2002), relatively few compounds with late alkali metal elements have been reported. Recently, we have discovered two K-containing rare earth borates, K3Y3(BO3)4 (Gao & Li, 2007a) and K3Y(BO3)2 (Gao & Li, 2007b) in the K2O—Y2O3—B2O3 system. We report here the structure of the title compound, which, to our knowledge, is the first rubidium rare earth borate.
In the structure of Rb3Y2(BO3)3 (Fig. 1), atom Y1 adopts an octahedral coordination with six Y—O bonds in the range 2.169 (6)–2.336 (6) Å (Table 1) and a bond valence sum (BVS) of 3.07 (Brown & Altermatt, 1985). Atom Y2 is coordinated by seven O atoms in a distorted pentagonal bipyramid with five shorter Y—O bonds [ranging from 2.204 (6) to 2.362 (6) Å] and two slightly longer Y—O bonds [2.431 (6) and 2.507 (5) Å], and with a BVS value of 3.12. As shown in Fig. 2(a), the basic structural unit of Rb3Y2(BO3)3 is a [Y2O10] dimer formed by face-sharing of the Y1O6–Y2O7 polyhedra. Such a face-sharing unit can also be found in Na2Gd2O(BO3)2 and K3Y3(BO3)4. The dimers share corners, forming a zigzag chain along the a direction, and the chain is reinforced by the B2O3 group, which uses all its three bonds to join neighbouring dimers (Fig. 2a). Along the b and c directions, these chains are connected to each other via the B1O3 and B3O3 groups, respectively, thereby constructing a three-dimensional framework. Atoms Rb1 and Rb2 are located in the larger channels and the Rb3 atom sits in the smaller channels along the a direction (Fig. 2b). The three Rb atoms are found to coordinate to seven, four and six O atoms (with BVS values of 1.00, 0.67 and 1.19, respectively), if the Rb—O contacts longer than those of Rb to B [Rb···B = 3.114 (9)–3.191 (11) Å] are neglected.
The mean O—B—O bond angles for the BO3 groups are all equal to 120°. The B3O3 group, which connects two Y1O6 octahedra and one Y2O7 pentagonal bipyramid from three different dimers, has a more regular triangular coordination, with a mean B3—O bond length of 1.371 Å [range 1.370 (10)–1.374 (11) Å], whereas the other two BO3 groups both contain two O atoms from single Y2O7 polyhedra and show a more distorted triangular coordination, with B—O bond lengths ranging from 1.354 (12) to 1.408 (12) Å.
Both Li3Nd2(BO3)3 and Na3La2(BO3)3 are closely related to the title compound in stoichiometry, but they differ in structure. They crystallize in the monoclinic space group P21/n and orthorhombic space group Amm2, respectively. In those structures, because of their larger ionic sizes, Nd and La atoms adopt nine-coordinated REO9 (RE is the rare earth element) polyhedra, which are different from those of the title compound. Similar coordination environments for the Y atoms can be found in K3Y3(BO3)4 and K3Y(BO3)2 reported recently by us. In K3Y3(BO3)4, the Y atoms coordinate to seven or eight O atoms and the seven-coordinate YO7 polyhedron, a pentagonal bipyramid, is similar to Y2O7 in Rb3Y2(BO3)3. In K3Y(BO3)2, the Y atoms are coordinated by six O atoms in an octahedron, which is also similar to the Y1O6 polyhedron in Rb3Y2(BO3)3. Considering the Y—O coordination only, it seems that the title compound is in a transition stage between K3Y(BO3)2 and K3Y3(BO3)4, which is also inferred by the ratios of alkali metal to rare earth elements in the chemical formula. This observation reiterates our early findings that the rare earth element tends to possess a more compact (with less oxygen) coordination with smaller size of the rare earth element and higher alkali metal content.
Although the title compound has a noncentrosymmetric structure, second harmonic generation (SHG) tests performed on crushed crystals using Kurtz methods (Kurtz & Perry, 1968) with a 1064 nm laser source failed to show an observable second-harmonic signal at 532 nm. Theoretical calculations based on a group approximation (Chen et al., 1989, 1990) show that the SHG coefficients are d31 = -0.08 pm V-1, d32 = -0.17 pm V-1 and d33 = 0.25 pm V-1, and only the B3O3 group makes a significant contribution (95% to d33 and 58% to d32). Both B1O3 and B2O3 are arranged in such a way that their contributions to the SHG coefficients are cancelled out by equivalent groups oriented in the opposite directions.