Tellurium compounds structure

Intramolecular heteroatom coordination may also influence the stabilities or structures of catenated tellurium compounds. For example, a rare example of a tritelluride, bis[2-(2-pyridyl)phenyl]tritelluride, is stabilized by a Te N contact of 2.55 The ditelluride (2-MeOCelFtCOTe) has an unusual planar structure. Although the C=0 Te interaction is longer (3.11 A) than the Me 0 contact (2.76 A), ab initio molecular orbital calculations indicate that the planarity results predominantly from the former intramolecular connection. 

A number of selenium and tellurium compounds of the presently discussed metals show a quite different behavior from the Fe-S system. Iron and selenium form two compounds FeSe with a broad stoichiometry range and FeSe2 with a much narrower composition field. Below 400 the non-stoichiometric Fei xSe exists by creation of iron vacancies and can have compositions lying between FeySes and Fe3Se4. At low temperatures there exist two phases an a (PbO type) and a f) (NiAs type) phase. The crystal sUiicture of the diselenide, FeSe2, is an orthorhombic, C18 (marcasite) type. In the Fe-Te system, the defect NiAs structure is found at a composition close to FeTei.s, as about one-third of the Fe atoms are missing. At compositions around FeTe the behavior is complex, and the f)-phase has the PbO structure (like FeSe) but with additional metal atoms (i.e., FeuTe). 

Multicomponent reactions (MCRs) have been known to produce highly complex and diverse structures [76]. There is a considerable interest in the application of new multicomponent reactions to access biologically relevant molecules [77,78] and natural products [79]. A recent report has disclosed multicomponent Passerini and Ugi reactions to produce, rapid and efficiently, a library of redox-active selenium and tellurium compounds [80]. The compounds showed promising cytotoxicity against several cancer cell lines. 

The tetrafluorides of selenium and tellurium are similar to SF4 both structurally (in the gaseous molecules) and in terms of reactivity, ffowever, the bonding in condensed phases is different and leads to several types of structures. Selenium tetrafluoride can be prepared by combining the elements, but it can also be obtained by the reaction of Se02 with SF4 at high temperature. The tellurium compound can be prepared by the reaction of SeF4 and Te02 at 80 °C. 

Magnetic Hyperfine Structure. The magnetic fields in most magnetic iodine and tellurium compounds are not sufficient to separate the 18 magnetic hyperfine lines of the two iodine isotopes. Several measurements (13, 21, 34, 36) have indicated that fields of only about 100 kilo-gauss can be expected from such compounds. Therefore, other methods must be utilized. 

In a forthcoming paper entitled Structural Studies of some Tellurium Compounds Using the Mossbauer Effect in and Nuclei by... 

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. ... 

Organotellurols 1, the tellurium analogs of alcohols, constitute a class of organic tellurium compounds, which have to be prepared and used in situ due to their high succeptibility to oxidation. The participation of this class of compounds in several reactions has been proposed,5-12 but their real existence has never been demonstrated in such processes. A few tellurols exhibiting special structural features could be isolated and characterized (e.g., compound 10, Figure 2).14... 

The divalent tellurium compounds with a C —Te —Y (Y = S, Se) unit in the molecule are stabilized by coordination of tellurium to an electronegative atom appropriately placed in the molecule. Formyl, pyridyl, or azo groups in an or/fto-position to the tellurium atom in phenyl tellurium compounds provide these coordination sites. X-ray structural investigations of such compounds revealed short Te—O and Te —N contacts2-4. 

In earlier work,i 3 Allinger et al. determined MM2 parameters for organoselenium and -tellurium compounds. The selenium parameters were fit to structures and vibrational frequencies of methyl selenol, dimethyl selenide, ethyl selenol, and tetrahydroselenophene. The structures of the tellurium analogs were also calculated, but since only a bond length for Te—C and a bond angle for C-Te-C from dimethyltelluride were known, the authors were unable to compare the results to experimental data. 

To determine the structures of selenium and tellurium compounds, it is convenient to know natural abundance ratios of their isotopes. For selenium, for example, °Se and Se are present in the ratio of 2 1, and this is indicative of the characteristic features of selenium compounds in mass spectra (i.e. monoselenides, M M -2 = 2 1 diselenides, M M -2 = 1 1). Furthermore, satellites based on fhe NMR-active " Se nuclei are helpful for assignment of carbon signals adjacent to Se in NMR. 

The three methanesulfonyl derivatives, sulfur, selenium, and tellurium dimethanethiosulfonates, are isomorphous. Structure analyses have been carried out, starting with tellurium dimethanethiosulfonate and using tellurium as a heavy atom in the first stages. So far, the structure of the tellurium compound has been published in detail 128), and an electron density projection along the short crystal axis of the trisulfide (98) has shown the unbranched sulfur chain structure. 

This family of compounds has been extensively studied in recent years. Wheeler has analyzed the electronic structure of Ni9(//4-Te)6(PEt3)8 with EH calculations. Hoffmann and coworkers have also used EH calculations to examine the electronic structure of this molecular cubic cluster to draw relationships with nickel-tellurium extended structures. More recently, we have performed EH and Xa calculations to rationalize the bonding in these clusters, as a function of different parameters such as the electron count or the nature and the size of the different elements constituting the cluster cage. " For symmetry reasons, a localized two-center-two-electron... 

Tellurium, tris(diethyldithiocarbamato)phenyl-stereochemistry, 82 Tellurium(II) complexes bis(dithiochelatc), 60 six-coordinate compounds structure, 53... 

Pauling But Matt, I m sure that you would be careful. Why don t you think it over and let me know if you would like to work on the structure of some tellurium compounds ... 

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