Methanolothermal Design and Structure of Cesium Polyselenidotellurates Cs4TexSe16−x(x=1, 4) and Cs4Te9.74Se13.26with Ordered Se/Te Rings and Chains
✍ Scribed by Michael Wachhold; William S. Sheldrick
- Book ID
- 102974794
- Publisher
- Elsevier Science
- Year
- 1997
- Tongue
- English
- Weight
- 823 KB
- Volume
- 134
- Category
- Article
- ISSN
- 0022-4596
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✦ Synopsis
The methanolothermal reaction of Cs 2 CO 3 with Se in the presence of Bi 2 Te 3 at 160°°C yields two tellurium-poor mixed polychalcogenides of the general type Cs 4 Te x Se 16؊x . Cs 4 TeSe 15 is isostructural with Cs 4 Se 16 and crystallizes in the orthorhombic space group Pbcm with a ؍ 10.042(2), b ؍ 14.029(3), c ؍ 19.120(4) A s , Z ؍ 4, and V ؍ 2693.6(10) A s 3 . It contains discrete [TeSe 15 ] 4؊ anions, in which a central Te atom is coordinated in a distorted square-planar manner by three Se 2؊ 5 chains, one of which is chelating. Cs 2 Te 2 Se 6 crystallizes in the monoclinic space group P2 1 /c with a ؍ 7.436(1), b ؍ 6.771(1), c ؍ 13.489(3) A s , ؍ 95.55(3)°°, Z ؍ 2, and V ؍ 676.0(2) A s 3 and is isostructural with Cs 2 Te 8 . If distances longer than 2.90 A s are ignored, the anionic structure may be described as a discrete [Te 2 Se 6 ] 2؊ chain in which the Te atoms adopt the third and sixth positions. Individual chains are connected through Te 2 Se interactions of lengths 2.922(2) and 3.244(1) A s into sheets. When Sb 2 Te 3 is employed in place of Bi 2 Te 3 , reaction of Cs 2 CO 3 with Se yields Cs 4 [TeSe 3 ] 2 • Te 3 Se 3 • 1.5(Te 3.21 Se 2.79 ) in which pyramidal [TeSe 3 ] 2؊ anions and respectively ordered and disordered Te x Se 6؊x rings are connected through secondary Te 2 Se bonds into polymeric layers. Cs 4 Te 9.74 Se 13.26 crystallizes in the rhombohedral space group R3 with a ؍ b ؍ 12.022(2), c ؍ 44.072(9) A s , Z ؍ 6, and V ؍ 5516(2) A s 3 .