Tellurium chloride structure

In the sulphides, selenides, tellurides and arsenides, all types of bond, ionic, covalent and metallic occur. The compounds of the alkali metals with sulphur, selenium and tellurium form an ionic lattice with an anti-fluorite structure and the sulphides of the alkaline earth metals form ionic lattices with a sodium chloride structure. If in MgS, GaS, SrS and BaS, the bond is assumed to be entirely ionic, the lattice energies may be calculated from equation 13.18 and from these values the affinity of sulphur for two electrons obtained by the Born-Haber cycle. The values obtained vary from —- 71 to — 80 kcals and if van der Waal s forces are considered, from 83 to -- 102 kcals. 

Crystal structures of ort/io-substituted phenyl tellurium halides and of 1-phenyl-3-(4 -methoxyphenyl)-l-propen-l-yl tellurium chloride clearly show that tellurium interacts with the heteroatom, thus stabilizing the compounds. In the absence of a stabilizing group in the ortho-y>o% i on, aryl tellurium halides are probably polymeric as solids and in solution with... 

The reaction of Me3SiN=S=NSiMe3 with TeC is a fruitful source of tellurium-nitrogen chlorides that also contain sulfur, as depicted by structures... 

The simplest recording medium is a bilayer structure. It is constructed by first evaporating a highly reflective aluminum layer onto a suitable disk substrate. Next, a thin film (15-50 nm thick) of a metal, such as tellurium, is vacuum deposited on top of the aluminum layer. The laser power required to form the mark is dependent on the thermal characteristics of the metal film. Tellurium, for example, has a low thermal diffusivity and a melting point of 452 °C which make it an attractive recording material. The thermal diffusivity of the substrate material should also be as low as possible, since a significant fraction of the heat generated in the metal layer can be conducted to the substrate. For this reason, low cost polymer substrates such as poly (methylmethacrylate) or poly (vinyl chloride) are ideal. 

Two types of three-coordinate selenium(II) complexes, isolated as the triselenocyanate and the triselenourea salts, and which have essentially similar structures, have been identified.66 Several three-coordinate tellurium(II) complexes have also been obtained67 when one of the ligands has a very strong trans effect, for example a phenyl group, as in phenylbis(thiourea)tellurium(II) chloride.68... 

However, an X-ray crystal study of one of the derivatives of 21, 3-phenyl-5-(4-methoxyphenyl-1,2-oxatellurolyl-l-ium chloride 21 (R = Ph, Ar = C6H4OMe-4) justifies its T-shaped tricoordinate tellurium structure (83JA875), which is portrayed in Fig. 4. 

Square-planar, four-coordinate tellurium(II) complexes, whose structural chemistry has recently been summarized by Foss 89>, offer illustrations of this highly approximate, constant-volume rule. Fig. 27 is a drawing, approximately to scale, of a schematic, electron-domain representation of a section through the 1 1 complex of benzenetellurenyl chloride with thiourea 90>. Shown are the electron domains of the tellurium kernel (largest, nearly centrally located solid circle) the ligands kernels (two chlorine kernels, a sulfur kernel of thiourea, and a carbon kernel of benzene) and the domains of the tellurium atom s shared valence-shell electrons (open circles) and, most schematically of all, the tellurium atom s unshared valence-shell electrons (shaded region). 

The platinum metal chalcogenides in general are easier to prepare than the corresponding oxides. Whereas special conditions of temperature and pressure are required to prepare many of the oxides, the platinum metals react most readily with S, Se, and Te. A number of additional differences concerning the chemistry of the chalcogenides and the oxides are summarized as follows The metal—sulfur (selenium, tellurium) bond has considerably more covalent character than the metal-oxygen bond and, therefore, there are important differences in the structure types of the compounds formed. Whereas there may be considerable similarity between oxides and fluorides, the structural chemistry of the sulfides tends to be more closely related to that of the chlorides. The latter compounds... 

Oxatellurolium compounds are stable in air as solids and in solution. They are not decomposed by light. Thermolysis at temperatures up to 300° and irradiation with unfiltered light from a Hanovia 450-V lamp failed to deposit tellurium. An X-ray structural study of 5-f4-methoxyphenyl)-3-phenyl-1,2-oxatellurolium chloride showed the Cl — Te —O bonds to be linear and to have bond orders of approximately 0.5. ... 

In the series of the binary halides of selenium and tellurium, the crystal structure determinations of tellurium tetrafluoride (100) and of tellurium tetrachloride on twinned crystals (65, 66) were the key to understanding the various and partly contradictory spectroscopic and other macroscopic properties (e.g., 66,161,168,169,219,220, 412), as well as the synthetic potential of the compounds. In contrast to the monomeric molecular i//-tbp gas phase structures with C2v symmetry (417), the solid state structures of both are polynuclear. As the prototype of the chlorides and bromides of selenium and tellurium, crystalline tellurium(IV) chloride has a cubane-like tetrameric structure with approximate Td symmetry (Fig. 1). Within the distorted TeCla+a octa-hedra the bonds to the triply bridging chlorine ligands are much longer than to the terminal chlorines. The bonding system can be described either covalently as Te4Cli6 molecules, or, in an ionic approximation, as [(TeCl Cn4] with a certain degree of stereochemical activity of the lone pairs toward the center of the voluminous cubane center (65, 66). 

Fig. 2. Comparison of the molecular structures of the tellurium(IV) fluoride, chloride, and iodide types in the solid state. The selenium(IV) chlorides and bromides as well as tellurium(IV) bromide and one of the five forms of tellurium(lV) iodide are isostructural to the cubane-like Te4Cli6 molecules (244).

Dibenzylidene-l, 3-ditelluretane was prepared by reacting tellurium with sodium phenylacetylide and acidifying the resulting mixture, which contains sodium phenylethyne-tellurolate, with hydrogen chloride in diethyl ether The structure of the compound was confirmed by single crystal X-ray analysis . The earlier reported formulation of this compound as 2-benzylidene-4-phenyl-l,3-ditelluracyclopent-4-ene is incorrect. ... 

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