Group 16 elements tellurium

Vol 12 PerfluorohaloorganiL Compounds of Main Group Elements Part 2 Compounds of Sulfur (Cuniinuanon) Selenium and Tellurium... 

N,N -Chelation is also exhibited by the dianionic P(III)/P(V) ligands (25) in the MejSn complex (31) [39] and in the magnesium complex (32) [40], which is prepared by oxidation of [Mg(thf)2[ BuNP(p-N Bu)2PN Bu] by elemental tellurium [40]. One of the endocychc N Bu groups in (32) is also weakly coordinated to magnesium, thus providing an intramolecular base-stabihzation similar to that observed for complexes of type (8). 

Wachsmann M, Heumann KG (1992) Negative thermal ionization mass spectrometry of main group elements, part 2. 6th group Sulfur, selenium, and tellurium. Int J Mass Spectrom Ion Proc 114 209-220... 

Among the oxygen group elements, while sulfur is oxidized to +6 oxidation state (in H2SO4), selenium and tellurium are oxidized to +4 oxyacids with the liberation of nitrogen dioxide ... 

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 chapter has been sectioned according to the paired combinations of N—O, N—S, S—O or Se containing bidentates. Another Group VI donor element, tellurium, has not been included since in only one example has this element formed part of a mixed donor bidentate. This is the reported interaction of di(o-aminophenyl)ditelluride (2) with Cu1 and Cu11, where N—Te bidentate behaviour was concluded for the tetrahedral Cu (N—Te)2 chelate.1... 

The scarcity of compounds involving the heavier main-group elements and the early transition metals, apparent in previous discussions, is also apparent in the chemistry of tellurium. Thiele (147) has described the preparation of the zirconium complex [ Zr(C5Me5)2(/i-Te) 2], 152, from a divinyl complex... 

Tellurium tetrachloride 16 was widely used in the past to introduce tellurium into organic substrates. It reacts with several functional groups giving organotellurium trichlorides 5 (X = C1), which constitute an important class of tellurium electrophiles. Tellurium tetrachloride 16 is prepared by passing a stream of dry chlorine over elemental tellurium in an appropriate glass apparatus (Equation (3)). 

Elemental tellurium and bis[di-t-butylphosphano]sulfur diimide in tetrahydrofuran at — 20° produced a dark-brown compound that quickly deposited tellurium from a solution at room temperature. Data from field-desorption mass spectrometry and 31P-NMR spectroscopy suggest an eight-membered ring with a tritelluro group as the structure for this brown compound2. 

The interest in coordination compounds containing transition metal-main group element bonds led to the preparation of tellurium derivatives, in which a bare tellurium atom is bonded to and bridges transition metal atoms such as Zr, Ilf, V, Cr, Mo, W, Mn, Re, Fe, Os, Co,... 

The P —Te and As —Te bonds were not attacked by water5,6 or methanol5. Trimethyl-stannane similarly cleaved the group V element-tellurium bonds in these compounds5 and in their coordination compounds with chromium and molybdenum carbonyls7. 

Chloroalkyl tellurium trichlorides are generally not reduced to ditellurium derivatives by aqueous sodium sulfide. /l /i-elimination of chloride and the trichlorotelluro group forms olefins3,4. 2-Chloro-2-phenylethenyl tellurium trichloride decomposed to elemental tellurium upon treatment with sodium sulfide nonahydrate2. 

S. Yali, G. Xiyun, D. Andao, Determination of platinum group elements by inductively coupled plasma-mass spectrometry combined with nickel sulphide E>re assay and tellurium coprecipitation, Spectrochim. Acta, 53B (1998), 1463D1467. 

Electrodeposition of Main Group Elements and Transition Metals. The electrodeposition of tellurium, Te, has been investigated in an acidic EMlCl-ZnCl2 ionic liquid [84]. Tellurium tetrachloride, TeCLi, is soluble in the ionic liquid. The electrodeposition of metallic tellurium occurs at around 1 V vs. Zn/Zn(II). The formation of the Zn-Te alloys also occurs at more negative potentials. The further reduction of metallic tellurium to Te(—11) is reported as well just as in the chloroaluminate ionic liquid. 

The sixth-group elements sulfur, selenium, and tellurium are much less electronegative than their congener oxygen, which was discussed in Chapter 6, and their chemical properties are correspondingly distinctive. 

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