metal-organic compounds
κSe)tris(tetrahydrofuran-κO)thulium(III)
of tris(phenylselenolato-aDepartment of Chemistry, PO Box 3000, FI-90014 University of Oulu, Finland, and bMax-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470 Mülheim an der Ruhr, Germany
*Correspondence e-mail: risto.laitinen@oulu.fi
In the title compound, [Tm(C6H5Se)3(C4H8O)3], the TmIII atom lies on a threefold rotation axis and is coordinated by three phenylselenolate ligands and three tetrahydrofuran ligands leading to a distorted fac-octahedral coordination environment. The Tm—Se and Tm—O bond lengths are 2.7692 (17) and 2.345 (10) Å, respectively, and the bond angles are 91.32 (6)° for Se—Tm—Se, 92.6 (2) and 94.4 (2)° for Se—Tm—O, and 81.2 (3)° for O—Tm—O. In the crystal, the discrete complexes are linked by van der Waals interactions only. The crystal was refined as a non-merohedral twin (ratio = 0.65:0.35).
Keywords: crystal structure; thulium complex; phenylselenolate ligand.
CCDC reference: 1031290
1. Related literature
For the synthesis of the title compound, see: Lee et al. (1998). For the crystal structures of the isotypic compounds [Er(SePh)3(THF)3] and [Yb(SePh)3(THF)3], see: Lee et al. (1998); Geissinger & Magull (1995). For a binuclear selenolate complex of thulium, see: Lee et al. (1995).
2. Experimental
2.1. Crystal data
|
Data collection: COLLECT (Bruker, 2008); cell DENZO-SMN (Otwinowski & Minor, 1997); data reduction: DENZO-SMN; program(s) used to solve structure: SIR92 (Altomare et al., 1993); program(s) used to refine structure: SHELXL2013 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2006); software used to prepare material for publication: WinGX (Farrugia, 2012).
Supporting information
CCDC reference: 1031290
10.1107/S1600536814023733/su5009sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536814023733/su5009Isup2.hkl
The title compound was synthesized by the literature procedure [Lee et al. (1998)]. The crystals were obtained from THF at 255 K.
H atoms were positioned geometrically and refined using a riding model with C—H = 0.95 - 0.99 Å and with Uiso(H) = 1.2Ueq(C). The crystal is a non-merohedral with
of -1 0 0, 0 -1 0, 0 0 1 and a ratio of 0.65:0.35. The THF ligands show positional disorder with an occupancy ratio of 0.79 (3):0.21 (3).Data collection: COLLECT (Bruker, 2008); cell
DENZO-SMN (Otwinowski & Minor, 1997); data reduction: DENZO-SMN (Otwinowski & Minor, 1997); program(s) used to solve structure: SIR92 (Altomare et al., 1993); program(s) used to refine structure: SHELXL2013 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2006); software used to prepare material for publication: WinGX (Farrugia, 2012).The molecular structure of the title compound, with atom labelling. Displacement ellipsoids are drawn at the 50% probability level. Only the more abundant orientation of the disordered THF ligands is shown (symmetry codes: (i) x, y, z; (ii) -y, x-y, z; (iii) -x + y, -x, z; (iv) y, x, z + 1/2; (v) x-y, -y, z + 1/2; (vi) -x, -x + y, z + 1/2. A perspective view along the c axis of the crystal packing of the title compound. |
[Tm(C6H5Se)3(C4H8O)3] | Dx = 1.782 Mg m−3 |
Mr = 853.42 | Mo Kα radiation, λ = 0.71073 Å |
Trigonal, P31c | Cell parameters from 2053 reflections |
a = 15.277 (2) Å | θ = 3.1–28.1° |
c = 7.8708 (16) Å | µ = 6.25 mm−1 |
V = 1590.9 (6) Å3 | T = 120 K |
Z = 2 | Block, pale yellow-green |
F(000) = 828 | 0.40 × 0.20 × 0.10 mm |
Bruker–Nonius KappaCCD diffractometer | 2053 reflections with I > 2σ(I) |
ϕ scans, and ω scans with κ offsets | Rint = 0.053 |
Absorption correction: multi-scan (XPREP in SHELXTL; Sheldrick, 2008) | θmax = 28.1°, θmin = 3.1° |
Tmin = 0.189, Tmax = 0.574 | h = −16→20 |
5660 measured reflections | k = −18→14 |
2151 independent reflections | l = −9→10 |
Refinement on F2 | H-atom parameters constrained |
Least-squares matrix: full | w = 1/[σ2(Fo2) + 8.380P] where P = (Fo2 + 2Fc2)/3 |
R[F2 > 2σ(F2)] = 0.038 | (Δ/σ)max < 0.001 |
wR(F2) = 0.087 | Δρmax = 0.76 e Å−3 |
S = 1.10 | Δρmin = −1.43 e Å−3 |
2151 reflections | Extinction correction: SHELXL2013 (Sheldrick, 20008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
127 parameters | Extinction coefficient: 0.0089 (14) |
9 restraints | Absolute structure: Flack x determined using 812 quotients [(I+)-(I-)]/[(I+)+(I-)] (Parsons & Flack, 2004) |
Hydrogen site location: inferred from neighbouring sites | Absolute structure parameter: −0.03 (3) |
[Tm(C6H5Se)3(C4H8O)3] | Z = 2 |
Mr = 853.42 | Mo Kα radiation |
Trigonal, P31c | µ = 6.25 mm−1 |
a = 15.277 (2) Å | T = 120 K |
c = 7.8708 (16) Å | 0.40 × 0.20 × 0.10 mm |
V = 1590.9 (6) Å3 |
Bruker–Nonius KappaCCD diffractometer | 2151 independent reflections |
Absorption correction: multi-scan (XPREP in SHELXTL; Sheldrick, 2008) | 2053 reflections with I > 2σ(I) |
Tmin = 0.189, Tmax = 0.574 | Rint = 0.053 |
5660 measured reflections |
R[F2 > 2σ(F2)] = 0.038 | H-atom parameters constrained |
wR(F2) = 0.087 | Δρmax = 0.76 e Å−3 |
S = 1.10 | Δρmin = −1.43 e Å−3 |
2151 reflections | Absolute structure: Flack x determined using 812 quotients [(I+)-(I-)]/[(I+)+(I-)] (Parsons & Flack, 2004) |
127 parameters | Absolute structure parameter: −0.03 (3) |
9 restraints |
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. Refined as a 2-component twin. |
x | y | z | Uiso*/Ueq | Occ. (<1) | |
Tm1 | 0.6667 | 0.3333 | 0.08579 (18) | 0.0326 (3) | |
Se1 | 0.63991 (14) | 0.46785 (13) | −0.11260 (16) | 0.0456 (4) | |
O1 | 0.7727 (7) | 0.4562 (7) | 0.2822 (12) | 0.034 (2) | |
C1 | 0.7309 (12) | 0.5979 (12) | −0.0110 (17) | 0.040 (4) | |
C2 | 0.6951 (13) | 0.6510 (11) | 0.081 (3) | 0.055 (4) | |
H2 | 0.6247 | 0.6222 | 0.1023 | 0.066* | |
C3 | 0.7629 (18) | 0.7463 (15) | 0.142 (2) | 0.069 (6) | |
H3 | 0.7377 | 0.7829 | 0.2025 | 0.082* | |
C4 | 0.8656 (14) | 0.7899 (15) | 0.119 (2) | 0.061 (6) | |
H4 | 0.9107 | 0.8545 | 0.1655 | 0.074* | |
C5 | 0.9021 (15) | 0.7375 (14) | 0.026 (2) | 0.056 (5) | |
H5 | 0.9725 | 0.7669 | 0.0057 | 0.067* | |
C6 | 0.8341 (15) | 0.6407 (12) | −0.038 (2) | 0.051 (5) | |
H6 | 0.8591 | 0.6043 | −0.0998 | 0.061* | |
C7A | 0.7418 (19) | 0.5034 (16) | 0.406 (2) | 0.044 (5) | 0.79 (3) |
H7AA | 0.6992 | 0.4534 | 0.4932 | 0.052* | 0.79 (3) |
H7BA | 0.7017 | 0.5302 | 0.3514 | 0.052* | 0.79 (3) |
C8A | 0.8335 (15) | 0.587 (2) | 0.487 (3) | 0.061 (8) | 0.79 (3) |
H8AA | 0.8218 | 0.5946 | 0.6082 | 0.074* | 0.79 (3) |
H8BA | 0.8556 | 0.6521 | 0.4276 | 0.074* | 0.79 (3) |
C9A | 0.9087 (15) | 0.5529 (15) | 0.465 (2) | 0.044 (6) | 0.79 (3) |
H9AA | 0.9009 | 0.5034 | 0.5539 | 0.053* | 0.79 (3) |
H9BA | 0.9789 | 0.6104 | 0.4666 | 0.053* | 0.79 (3) |
C10A | 0.879 (2) | 0.505 (3) | 0.293 (4) | 0.045 (7) | 0.79 (3) |
H0AA | 0.9104 | 0.5568 | 0.2032 | 0.055* | 0.79 (3) |
H0BA | 0.9021 | 0.4551 | 0.2782 | 0.055* | 0.79 (3) |
C7B | 0.743 (9) | 0.484 (8) | 0.454 (9) | 0.044 (5) | 0.21 (3) |
H7AB | 0.7077 | 0.5231 | 0.4379 | 0.052* | 0.21 (3) |
H7BB | 0.7010 | 0.4239 | 0.5246 | 0.052* | 0.21 (3) |
C8B | 0.850 (6) | 0.551 (8) | 0.532 (12) | 0.061 (8) | 0.21 (3) |
H8AB | 0.8521 | 0.6075 | 0.5967 | 0.074* | 0.21 (3) |
H8BB | 0.8655 | 0.5099 | 0.6107 | 0.074* | 0.21 (3) |
C9B | 0.928 (5) | 0.592 (6) | 0.386 (9) | 0.044 (6) | 0.21 (3) |
H9AB | 0.9961 | 0.6094 | 0.4276 | 0.053* | 0.21 (3) |
H9BB | 0.9320 | 0.6533 | 0.3350 | 0.053* | 0.21 (3) |
C10B | 0.888 (7) | 0.505 (13) | 0.26 (2) | 0.045 (7) | 0.21 (3) |
H0AB | 0.9122 | 0.4568 | 0.2814 | 0.055* | 0.21 (3) |
H0BB | 0.9084 | 0.5304 | 0.1378 | 0.055* | 0.21 (3) |
U11 | U22 | U33 | U12 | U13 | U23 | |
Tm1 | 0.0385 (3) | 0.0385 (3) | 0.0206 (4) | 0.01927 (16) | 0.000 | 0.000 |
Se1 | 0.0548 (9) | 0.0551 (10) | 0.0316 (7) | 0.0311 (9) | −0.0015 (8) | 0.0096 (8) |
O1 | 0.036 (5) | 0.041 (6) | 0.024 (4) | 0.020 (5) | 0.007 (4) | 0.001 (4) |
C1 | 0.054 (11) | 0.045 (8) | 0.028 (8) | 0.031 (8) | 0.005 (7) | 0.017 (6) |
C2 | 0.070 (10) | 0.056 (10) | 0.052 (9) | 0.041 (9) | 0.036 (12) | 0.019 (11) |
C3 | 0.13 (2) | 0.072 (13) | 0.042 (9) | 0.077 (15) | 0.016 (11) | 0.012 (9) |
C4 | 0.066 (12) | 0.045 (9) | 0.054 (13) | 0.013 (8) | −0.005 (8) | −0.007 (8) |
C5 | 0.061 (11) | 0.045 (9) | 0.069 (12) | 0.033 (9) | 0.012 (8) | 0.006 (9) |
C6 | 0.045 (10) | 0.053 (9) | 0.043 (8) | 0.016 (9) | −0.009 (8) | −0.002 (6) |
C7A | 0.059 (11) | 0.048 (11) | 0.014 (9) | 0.020 (10) | 0.006 (11) | 0.010 (8) |
C8A | 0.064 (14) | 0.062 (18) | 0.038 (14) | 0.016 (12) | −0.003 (10) | −0.017 (12) |
C9A | 0.040 (11) | 0.043 (12) | 0.026 (10) | 0.004 (10) | 0.001 (9) | 0.011 (8) |
C10A | 0.053 (12) | 0.060 (11) | 0.03 (2) | 0.034 (10) | −0.001 (11) | 0.003 (13) |
C7B | 0.059 (11) | 0.048 (11) | 0.014 (9) | 0.020 (10) | 0.006 (11) | 0.010 (8) |
C8B | 0.064 (14) | 0.062 (18) | 0.038 (14) | 0.016 (12) | −0.003 (10) | −0.017 (12) |
C9B | 0.040 (11) | 0.043 (12) | 0.026 (10) | 0.004 (10) | 0.001 (9) | 0.011 (8) |
C10B | 0.053 (12) | 0.060 (11) | 0.03 (2) | 0.034 (10) | −0.001 (11) | 0.003 (13) |
Tm1—O1i | 2.345 (10) | C7A—C8A | 1.49 (2) |
Tm1—O1 | 2.345 (10) | C7A—H7AA | 0.9900 |
Tm1—O1ii | 2.345 (10) | C7A—H7BA | 0.9900 |
Tm1—Se1i | 2.7692 (17) | C8A—C9A | 1.49 (2) |
Tm1—Se1ii | 2.7692 (17) | C8A—H8AA | 0.9900 |
Tm1—Se1 | 2.7692 (17) | C8A—H8BA | 0.9900 |
Se1—C1 | 1.938 (18) | C9A—C10A | 1.50 (2) |
O1—C10A | 1.41 (3) | C9A—H9AA | 0.9900 |
O1—C7A | 1.42 (3) | C9A—H9BA | 0.9900 |
O1—C10B | 1.55 (10) | C10A—H0AA | 0.9900 |
O1—C7B | 1.56 (10) | C10A—H0BA | 0.9900 |
C1—C2 | 1.39 (2) | C7B—C8B | 1.55 (9) |
C1—C6 | 1.39 (3) | C7B—H7AB | 0.9900 |
C2—C3 | 1.38 (3) | C7B—H7BB | 0.9900 |
C2—H2 | 0.9500 | C8B—C9B | 1.55 (9) |
C3—C4 | 1.38 (3) | C8B—H8AB | 0.9900 |
C3—H3 | 0.9500 | C8B—H8BB | 0.9900 |
C4—C5 | 1.39 (2) | C9B—C10B | 1.55 (9) |
C4—H4 | 0.9500 | C9B—H9AB | 0.9900 |
C5—C6 | 1.41 (2) | C9B—H9BB | 0.9900 |
C5—H5 | 0.9500 | C10B—H0AB | 0.9900 |
C6—H6 | 0.9500 | C10B—H0BB | 0.9900 |
O1i—Tm1—O1 | 81.2 (3) | C8A—C7A—H7BA | 110.0 |
O1i—Tm1—O1ii | 81.2 (3) | H7AA—C7A—H7BA | 108.3 |
O1—Tm1—O1ii | 81.2 (3) | C7A—C8A—C9A | 102 (2) |
O1i—Tm1—Se1i | 94.4 (2) | C7A—C8A—H8AA | 111.4 |
O1—Tm1—Se1i | 92.6 (2) | C9A—C8A—H8AA | 111.4 |
O1ii—Tm1—Se1i | 173.0 (2) | C7A—C8A—H8BA | 111.4 |
O1i—Tm1—Se1ii | 92.6 (2) | C9A—C8A—H8BA | 111.4 |
O1—Tm1—Se1ii | 173.0 (2) | H8AA—C8A—H8BA | 109.2 |
O1ii—Tm1—Se1ii | 94.4 (2) | C8A—C9A—C10A | 100 (2) |
Se1i—Tm1—Se1ii | 91.32 (6) | C8A—C9A—H9AA | 111.7 |
O1i—Tm1—Se1 | 173.0 (2) | C10A—C9A—H9AA | 111.7 |
O1—Tm1—Se1 | 94.4 (2) | C8A—C9A—H9BA | 111.7 |
O1ii—Tm1—Se1 | 92.6 (2) | C10A—C9A—H9BA | 111.7 |
Se1i—Tm1—Se1 | 91.32 (6) | H9AA—C9A—H9BA | 109.5 |
Se1ii—Tm1—Se1 | 91.32 (6) | O1—C10A—C9A | 107.3 (17) |
C1—Se1—Tm1 | 103.4 (4) | O1—C10A—H0AA | 110.3 |
C10A—O1—C7A | 106.2 (19) | C9A—C10A—H0AA | 110.3 |
C10B—O1—C7B | 114 (7) | O1—C10A—H0BA | 110.3 |
C10A—O1—Tm1 | 127.8 (12) | C9A—C10A—H0BA | 110.3 |
C7A—O1—Tm1 | 125.8 (11) | H0AA—C10A—H0BA | 108.5 |
C10B—O1—Tm1 | 117 (4) | C8B—C7B—O1 | 100 (7) |
C7B—O1—Tm1 | 128 (4) | C8B—C7B—H7AB | 111.8 |
C2—C1—C6 | 119.4 (16) | O1—C7B—H7AB | 111.8 |
C2—C1—Se1 | 121.6 (13) | C8B—C7B—H7BB | 111.8 |
C6—C1—Se1 | 118.9 (12) | O1—C7B—H7BB | 111.8 |
C3—C2—C1 | 119.3 (16) | H7AB—C7B—H7BB | 109.5 |
C3—C2—H2 | 120.3 | C9B—C8B—C7B | 109 (7) |
C1—C2—H2 | 120.3 | C9B—C8B—H8AB | 110.0 |
C4—C3—C2 | 122.4 (17) | C7B—C8B—H8AB | 110.0 |
C4—C3—H3 | 118.8 | C9B—C8B—H8BB | 110.0 |
C2—C3—H3 | 118.8 | C7B—C8B—H8BB | 110.0 |
C3—C4—C5 | 118.7 (17) | H8AB—C8B—H8BB | 108.3 |
C3—C4—H4 | 120.7 | C8B—C9B—C10B | 105 (7) |
C5—C4—H4 | 120.7 | C8B—C9B—H9AB | 110.9 |
C4—C5—C6 | 119.8 (17) | C10B—C9B—H9AB | 110.9 |
C4—C5—H5 | 120.1 | C8B—C9B—H9BB | 110.9 |
C6—C5—H5 | 120.1 | C10B—C9B—H9BB | 110.9 |
C1—C6—C5 | 120.4 (17) | H9AB—C9B—H9BB | 108.9 |
C1—C6—H6 | 119.8 | C9B—C10B—O1 | 101 (7) |
C5—C6—H6 | 119.8 | C9B—C10B—H0AB | 111.7 |
O1—C7A—C8A | 108.6 (19) | O1—C10B—H0AB | 111.7 |
O1—C7A—H7AA | 110.0 | C9B—C10B—H0BB | 111.7 |
C8A—C7A—H7AA | 110.0 | O1—C10B—H0BB | 111.7 |
O1—C7A—H7BA | 110.0 | H0AB—C10B—H0BB | 109.4 |
C6—C1—C2—C3 | 1 (3) | C10B—O1—C10A—C9A | 170 (51) |
Se1—C1—C2—C3 | −176.1 (14) | C7B—O1—C10A—C9A | 3 (5) |
C1—C2—C3—C4 | −2 (3) | Tm1—O1—C10A—C9A | −163.7 (15) |
C2—C3—C4—C5 | 2 (3) | C8A—C9A—C10A—O1 | −37 (4) |
C3—C4—C5—C6 | −2 (3) | C10A—O1—C7B—C8B | 1 (7) |
C2—C1—C6—C5 | −1 (2) | C7A—O1—C7B—C8B | −103 (15) |
Se1—C1—C6—C5 | 176.5 (12) | C10B—O1—C7B—C8B | −2 (11) |
C4—C5—C6—C1 | 1 (3) | Tm1—O1—C7B—C8B | 168 (5) |
C10A—O1—C7A—C8A | 3 (3) | O1—C7B—C8B—C9B | 23 (10) |
C10B—O1—C7A—C8A | −3 (10) | C7B—C8B—C9B—C10B | −37 (14) |
C7B—O1—C7A—C8A | 85 (15) | C8B—C9B—C10B—O1 | 32 (14) |
Tm1—O1—C7A—C8A | −171.5 (13) | C10A—O1—C10B—C9B | −33 (38) |
O1—C7A—C8A—C9A | −27 (2) | C7A—O1—C10B—C9B | 1 (15) |
C7A—C8A—C9A—C10A | 37 (3) | C7B—O1—C10B—C9B | −19 (14) |
C7A—O1—C10A—C9A | 21 (4) | Tm1—O1—C10B—C9B | 170 (7) |
Symmetry codes: (i) −x+y+1, −x+1, z; (ii) −y+1, x−y, z. |
Experimental details
Crystal data | |
Chemical formula | [Tm(C6H5Se)3(C4H8O)3] |
Mr | 853.42 |
Crystal system, space group | Trigonal, P31c |
Temperature (K) | 120 |
a, c (Å) | 15.277 (2), 7.8708 (16) |
V (Å3) | 1590.9 (6) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 6.25 |
Crystal size (mm) | 0.40 × 0.20 × 0.10 |
Data collection | |
Diffractometer | Bruker–Nonius KappaCCD diffractometer |
Absorption correction | Multi-scan (XPREP in SHELXTL; Sheldrick, 2008) |
Tmin, Tmax | 0.189, 0.574 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 5660, 2151, 2053 |
Rint | 0.053 |
(sin θ/λ)max (Å−1) | 0.662 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.038, 0.087, 1.10 |
No. of reflections | 2151 |
No. of parameters | 127 |
No. of restraints | 9 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.76, −1.43 |
Absolute structure | Flack x determined using 812 quotients [(I+)-(I-)]/[(I+)+(I-)] (Parsons & Flack, 2004) |
Absolute structure parameter | −0.03 (3) |
Computer programs: COLLECT (Bruker, 2008), DENZO-SMN (Otwinowski & Minor, 1997), SIR92 (Altomare et al., 1993), SHELXL2013 (Sheldrick, 2008), DIAMOND (Brandenburg, 2006), WinGX (Farrugia, 2012).
Acknowledgements
EMT thanks the Jenni and Antti Wihuri Foundation for financial support.
References
Altomare, A., Cascarano, G., Giacovazzo, C. & Guagliardi, A. (1993). J. Appl. Cryst. 26, 343–350. CrossRef Web of Science IUCr Journals Google Scholar
Brandenburg, K. (2006). DIAMOND. Crystal Impact GmbH, Bonn, Germany. Google Scholar
Bruker (2008). COLLECT. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Farrugia, L. J. (2012). J. Appl. Cryst. 45, 849–854. Web of Science CrossRef CAS IUCr Journals Google Scholar
Geissinger, M. & Magull, J. (1995). Z. Anorg. Allg. Chem. 621, 2043–2048. CSD CrossRef CAS Web of Science Google Scholar
Lee, J., Brewer, M., Berardini, M. & Brennan, J. G. (1995). Inorg. Chem. 34, 3215–3219. CSD CrossRef CAS Web of Science Google Scholar
Lee, J., Freedman, D., Melman, J. H., Brewer, M., Sun, L., Emge, T. J., Long, F. H. & Brennan, J. G. (1998). Inorg. Chem. 37, 2512–2519. Web of Science CSD CrossRef CAS Google Scholar
Otwinowski, Z. & Minor, W. (1997). Methods in Enzymology, Vol 276. Macromolecular Crystallography, Part A, edited by C. W. Carter Jr & R. M. Sweet pp. 307–326. New York, Academic Press. Google Scholar
Parsons, S. & Flack, H. (2004). Acta Cryst. A60, s61. CrossRef IUCr Journals Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.