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Single Crystals of C–La2Se3, C–Pr2Se3, and C–Gd2Se3 with Cation-Deficient Th3P4-Type Structure

✍ Scribed by Matthias Folchnandt; Thomas Schleid

Publisher
John Wiley and Sons
Year
2001
Tongue
German
Weight
90 KB
Volume
627
Category
Article
ISSN
0372-7874

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✦ Synopsis

Ruby-red, bead-shaped single crystals of C-type La 2 Se 3 (a = 905.21(6) pm), Pr 2 Se 3 (a = 891.17(6) pm), and Gd 2 Se 3 (a = 872.56(5) pm) are obtained by oxidation of the respective rare-earth metal (M = La, Pr and Gd) with selenium (molar ratio 2 : 3) in evacuated silica tubes at 750 °C in the presence of fluxing CsCl within seven days. Their crystal structure belongs to a cation-deficient Th 3 P 4 -type variant (cubic, I 4 3d) according to M 2.667 & 0.333 Se 4 (Z = 4) or M 2 Se 3 (Z = 5.333) offering coordination numbers of eight (Se 2± ar-ranged as trigonal dodecahedra) to the M 3+ cations. In spite of the high Cs + activity in molten CsCl, no cesium incorporation into the M 5.333 & 0.667 Se 8 -frame structure (e. g. as CsM 5 Se 8 with Z = 2) could be achieved, judged from both results of electron beam X-ray microanalyses and refined occupation factors of the metal position very close to x = 8/9 for M 3x Se 4 .

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Benzo-1,2,3-triselenolium Trifluoro-meth
Benzo-1,2,3-triselenolium Trifluoro-methanesulfonate—a C2Se3 Radical Cationic Salt with Unusual Solid-State Structure
✍ Dr. Gotthelf Wolmershäuser; Dipl.-Chem. Gert Heckmann 📂 Article 📅 1992 🏛 John Wiley and Sons 🌐 English ⚖ 252 KB

Compound 3 can be compared with its carbocyclic analogue 4[l61 only in solution, since 4 was not structurally characterized. The z o 7 P b 1 H and 207Pb13C coupling constants of 3 (\*Jpb," = 33.6, lJpb,cz = 5.8, 1Jpb,c3 = 31.8 Hz) are smaller than those of 4, which might indicate a larger percentage