Tellurium crystal structure

Fig. 3.12 Two views of the normal tellurium crystal structure, side view (a) and view along the chain direction (b).

In contras t with dially lamines and their sulfonyl derivatives, IV-acy Idially lamines react with tellurium tetrahalides to give zwitterionic oxazolines 29 containing five-coordinated tellurium (85T1607). Molecular and crystal structures of one of this type of compound (29, R = Me, X = Cl) were studied by X-rays (85T1607). 

A new structure type is found for Ag2Hg(Se03)2. Both Ag+ and Hg2+ ions are in octahedral coordination in this compound.137 The polyhedra are linked by the pyramidal shaped selenite anions.138 In the crystal structure of the red tellurate Ag2Hg2(Te04)3, the tellurium atoms are in octahedral coordination of oxygen atoms, and the octahedra are linked to infinite chains running along the u-axis. 

Structural steels, tellurium in, 24 425 Structure(s), see also Chain structure Chemical structures Cocontinuous structures Controlled structure Crystal structure Molecular structure Morphology Phase structure of carbon fibers, 26 737-739 detersive systems for, 8 413t HDPE, 20 157-162 LLDPE, 20 182-184, 203-205 polyesterether elastomer, 20 72-73 polyester fiber, 20 21 polyether antibiotics, 20 137-139 polyimide, 20 276-278 polymer, 20 395-405 protein, 20 449 PTT, 20 68t... 

Sulphur, Selenium, and Tellurium Compounds.—The crystal structure of the metal-rich zirconium sulphide Zr Sj has been determined and each sulphur atom shown to be at the centre of a square antiprism of zirconium atoms. The reaction of ZrS2 with potassium in liquid ammonia has been shown to give four K ZrS2 phases (.x = 1, 0.86, 0.71, or 0.71—0.22) which differ in the nature of the co-ordination sites occupied by the potassium atoms between the ZrS2 layers. ZrCl reacts with NaS2P(OEt)2 in toluene to form [Zr S2P-(OEt)2 4], which appears to involve a trigonal-dodecahedral arrangement of sulphur atoms about the metal. ... 

Once Te-III was identified as incommensurate, subsequent analysis was conducted on the previously-collected powder-diffraction data using the formalism of 4D superspace [234], and the JANA2000 software for structure refinement [235]. The Rietveld refinement of the incommensurate Te-III diffraction profile is shown in Fig. 9, and the modulated structure is shown in Fig. 10. Tellurium was only the second element found to have a modulated crystal structure at high-pressure, the... 

Nickel—Iron and Cobalt—Iron Alloys. Sdenium improves the machinability of Ni—Fe and Co—Fe alloys which are used for dectrical applications. Neither sulfur nor tellurium are useful additives because these dements cause hot brittleness. The addition of 0.4—0.5% sdenium promotes a columnar crystal structure on solidification, doubling the coercive force of cobalt—iron—titanium alloy permanent magnets produced with an equiaxial grain structure. 

TELLURIUM. TCAS 13494-80-91. Chemical element, symbol Te, at. no. 52. at. wL 127.60, periodic table group 6, mp 450°C, bp 690°C, density 6.24 g/cm3 (crystalline form at 25°C), 6.00 (amorphous farm at 25°C). Elemental tellurium has a hexagonal crystal structure with trigonal symmetry. Tellurium is a silver-white brittle semi-metal, stable in air, and in boiling H2O, insoluble in HC1, but dissolved by HNOj or aqua regia to form telluric acid. The element is dissolved by NaOH solution and combines with chlorine upon heating to form tellurium tetrachloride. 

The chemistry of 1,3-diketone complexes of nonmetallic elements (B, Si, Ge, Sb, Te) has been reviewed.68 Condensation of acetylacetone with TeCl4 yields Te(CH2COCH2COCH2)Cl2 (8a), which may be reduced to Te(CH2COCH2COCFI2) (8b). The crystal structures of these compounds demonstrate an unusual coordination of tellurium to the terminal carbons of the diketonate.61 72 In the dichloride complex, Teiv exhibits a distorted trigonal bipyramidal geometry with a stereochemi-cally active lone electron pair in the equatorial plane. In S2(MeCOCHCOMe)2 the acetylacetonate methine carbons are bonded to a disulfur unit.73... 

The X-ray crystal structure determination of telluradiazole 39 showed that it exists as a weakly associated dimer in the solid state half of the dimer represents the asymmetric unit <1996IC9>. Selected bond distances and bond angles are summarized in Table 11. The intramolecular Te-N distances of 2.002(3) and 2.006(4) A are slightly shorter than the reported average distances of 2.02A for the parent 1,2,5-telluradiazole and phenanthro[9,10-c]-l,2,5-telluradiazole <1984AXC653>. The bond angle of 85.8(1)° at tellurium is comparable to the values of 82.5(5)° and 84.3(3)° found for the other telluradiazoles. These data indicate that the tellurium(ll) resonance form 40A is a more important contributor than the tellurium(rv) form 40B to the overall structure 39. 

In this chapter, the theoretical methods, crystal structures, characteristic nuclear magnetic resonances, reactivities, and formation of four-membered rings with two heteroatoms including selenium or tellurium that have appeared in the last decade are described. 

Crystal structures have been determined for a series of highly crowded bistricyclic selenium- and tellurium-bridged compounds 21-23 as well as a nonhindered analogue 24 <2000J(P2)725>. The conformational behavior of the selenoxanthylidene and telluroxanthylidene moieties within these molecules has been described (see Section 7.11.4.1). 

Crystal structures of ortho-substituted phenyl tellurium halides and of J-phenyl-3-(4 -methoxyphenyl)-l-propen-l-yl tellurium chloride6clearly show that tellurium interacts with the heteroatom, thus stabilizing the compounds. In the absence of a stabilizing group in the ortho-position, aryl tellurium halides are probably polymeric as solids and in solution with... 

Crystal structures of the dihalotellurates show that the molecules have a T shape with the halogens in a Irony-position to each other6 1. The chalcogenocyanate groups are bonded to tellurium via the chalcogen atom7. 

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