Tellurium compounds hydrolysis

When stirred for a few minutes with equimolar amounts of rm.-butyl hypochlorite in methanol/dichloromethane at 0° and then with aqueous sodium hydrogen carbonate solutions, diorgano tellurium compounds were converted in good yields to diorgano tellurium oxides1. The /ct/.-butanol formed during hydrolysis is easily removed under reduced pressure. 

Selenide precursors based on selenourea display similar hydrolysis reactions and effects of substitution N,N dimethylselenourea is for instance more stable than selenourea [5]. However, the reactivity of selenoureas, especially in contact with oxygen, is much larger than their sulfur analogues, making the use of these precursors more difficult. Tellurium compounds are even more reactive. To overcome this problem, reducing agents, like sulfite ions, have to be added to the bath [5]. 

It was noted that cross-linked polystyrene-telluric acid (a product of TeCl4 polycondensation with a copolymer of divinylbenzene and styrene and subsequent hydrolysis in an alkaline medium) is an active catalyst of olefin epoxidation by hydrogen peroxide [210]. At 333 K and in dioxane and terf-butanol solutions, the above catalyst quantitatively yielded epoxides from a wide range of unsaturated compounds such as aromatic and aliphatic hydrocarbons, alcohols and their derivatives. A plausible mechanism for the catalytic properties of a tellurium compound during polycondensation was discussed. 

Aryltellurinic acids were described in the early period of tellurium chemistry as the products of the alkaline hydrolysis of the trichlorides. However, the structure of these compounds was later argued about, and the corresponding anhydrides are today accepted as the unequivocal products.The anhydrides are stable, colourless, solids with high melting points and have recently attained a relevant role as synthetic reagents. 

The hydroxy methoxy tellurium tetrafluorides are surprisingly stable compounds. No hydrolysis or isomerization occurred in 96% sulfuric acid up to a temperature of 150°. The Pwi.v-compound seems to be thermodynamically more stable than the ds-derivative1. 

Organo tellurium trihalides are the best known and most numerous compounds among the tellurinic acid derivatives. Most of the other derivatives are represented only by a few compounds, some of which have not been adequately characterized. Frequently, different products are claimed for similar reactions with identical starting materials. Much more work needs to be done with the various hydrolysis products of organo tellurium halides before this area of organic tellurium chemistry can be considered to be adequately explored. 

The hydrolysis of phenyl tellurium pentafluoride with an equimolar amount of water in acetonitrile for one hour at 20 produced a 1 3 mixture of cis- and trcms pheriyl tellurium tetrafluoride hydroxides. The compounds were characterized by 19F-NMR spectroscopy. ... 

The freshly obtained products of the alkaline hydrolysis of several diaryl tellurium dichlorides were claimed to be dihydroxides that were dehydrated to diaryl tellurium oxides on heating to 100°13, on heating their solutions in organic solvents to 80°13, or on keeping the compounds for several hours at 20° 13. 

The HjC-O-Te bonds are remarkably stable no cis-trans isomerization was observed when the hydroxy methoxy tellurium tetrafluorides were kept at temperatures below 130°. The bonds are not cleaved by 65% oleum or chlorosulfonic acid at room temperature, instead, the sulfate esters HjCO-TeF tO-SOjH) were formed. These sulfate esters were transformed to HO-TeFiCO-SOjH) upon heating to 100°. Cesium chloride dissolved in an excess of cis- or /run.s-hydroxy methoxy tellurium tetrafluoride liberated hydrogen chloride with the formation of very hygroscopic cesium methoxo(oxo)letrafluorotellurates(VI). Trunj-hydroxy methoxy tellurium tetrafluoride reacts instantaneously with water with loss of fluoride. The cu-compound is stable toward hydrolysis at room temperature. ... 

The dihalides are susceptible to decomposition by hydrolysis. The dibromides oxidize thiols to disulfides, selenols to diselenides, and diphenyl tellurium to diphenyl tellurium oxide. Hydrazine reduces the dihalides to the parent compounds. ... 

Triseleno and tritellurio analogues have been prepared similarly [60,68]. The tris(methylseleno) compound closely resembles its sulphur analogue but the tellurium analogue differs spectroscopically and is less stable [60]. All develop noxious odours on exposure to air, consequent upon partial hydrolysis. N.m.r. spectra indicate conjugative interaction of the sulphur atoms with the cyclopropenium ring [67]. 

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