Tellurocyanate

A versatile route to 3-benzoheteropines has been reported starting from o-phthalaldehyde, including the first preparations of 3-benzarsepines and the parent 3-benzothiepin and 3-benzoselenepins <96CC2183>. l,7-Dihydro-l//-dibenzo[c,c]tellurepin has been prepared from 2,2 -bis(bromomethyl)biphenyl and potassium tellurocyanate and its complexes with palladium and ruthenium species have been studied, a number of mono- and binuclear complexes are formed <96RTC427>. 

However, selenium and tellurium do not react with hydrogen, so the hydrogen compounds are prepared by reacting the elements with a metal, then treating it with an acid. Selenium and tellurium undergo addition reactions with cyanides to yield selenocyanates and tellurocyanates ... 

Another method that uses arenediazonium fluoroborates to prepare diaryl tellurides is the reaction with potassium tellurocyanate. Aryl teUurocyanides are postulated as intermediates. 

Aryl tellurocyanates are easily prepared by reacting aryltellurenyl bromides (generated in situ by reduction of the corresponding tribromides) with potassium cyanide. ... 

The stable (o-nitrophenyl) teUurenyl bromide reacts directly with potassium cyanide to give the corresponding tellurocyanate. 

A useful modification of the bis(p-methoxyphenyl) telluroxide reagent is its immobilization on a polymeric resin. This polymer-supported reagent, prepared from p-methoxyphenyl tellurocyanate and polylp-Uthiostyrene), exhibits several advantages over the monomeric reagent, such as easier product work-up and multiple recycle from the spent reagent. 

Dibenzyl ditelluride, benzyl telluride and benzyl tellurocyanate generate benzyl bromide on treatment with excess bromine. 

The group VIB cyanides, thiocyanates and selenocyanates and their complexes with species such as thiourea have been described.1,45 For example, the tellurium dithiocyanate complex has been prepared45 by treatment of tellurium dichloride or tellurium dibromide with ammonium thiocyanate. It seems that little information exists on the preparation of tellurocyanates and there is a sparsity of data on polonium derivatives. Indeed, the only known cyanide of polonium is probably a salt of the quadrivalent element.1... 

Triazenes, sulfur diimines, azides, cyanates, thiocyanates, selenocyanates and tellurocyanates 793... 

Tellurocyanate complexes of silver(I) have not been reported. 

Another approach to aryl tellurides involving nucleophilic tellurium species consists in the use of aryldiazonium salts as substrates. Arenediazonium tetrafluoroborates 64 react with sodium telluride,128 potassium tellurocyanate 65, sodium 0,0-diethylphosphorotellurolate 66, or aryl tellurolate 2 to give the corresponding diaryl tellurides 3 in moderate yields (Scheme 33).129,130... 

Tetraphenylarsonium tellurocyanate and triphenylphosphane in acetonitrile formed bis[triphenylphosphane] tellurium3. 

Bis[triphenylphosphane] Tellurium3 1.0 g (1.86 mmol) of tetraphenylarsonium tellurocyanate is dissolved in 20 ml of purified acetonitrile and 2.0 g (7.64 mmol) of triphenylphosphane are added under nitrogen. Then a solution of 0.34 g (3.2 mmol) of lithium perchlorate in 10 m/of acetonitrile is added dropwise, the mixture is stirred at 20° for several min, 2.0 g of triphenylphosphane dissolved in 15 ml of acetonitrile are added, and the mixture is stirred at 35° until the white precipitate has dissolved. The mixture is then filtered to collect the remaining yellow solid. This solid is dissolved in 20 ml of acetone containing 3.0 g of triphenylphosphinc, the mixture is filtered, and the filtrate is kept at 0° for several hours until the first crystals of triphenylphosphine appear. The mixture is then filtered rapidly, the solid is washed with ice-cold acetone containing triphenylphosphine, and the solid is dried yield 0.36 g (30%) m.p. 83-85° (dec.). 

Although the tellurocyanate ion was suspected for a long time to exist in solution, attempts to isolate tellurocyanates had failed3 until 1968, when tetraethylammonium tellurocyanate was isolated as a moisture- and air-sensitive, pale-yellow solid. Several other tellurocyanates with large onium cations were subsequently isolated. 

Although alkali metal cyanides react with tellurium in liquid ammonia4 or in dimethyl sulfoxide5 8 under an inert atmosphere, alkali metal tellurocyanates cannot be isolated from such solutions. Evaporation of the solvent leaves a residue of tellurium and the... 

The crude products are obtained in almost quantitative yields. Purification of the tellurocyanates by recrystallization causes considerable losses by decomposition. 

Tetraphenylarsonium tellurapentathionate reacted readily in acetonitrile with tetra-phenylphosphonium cyanide to produce tellurocyanate9. The tellurocyanate was not isolated. 

Tellurocyanate ion reacts with benzyl halides1-3, aryl iodides10, arenediazonium tetraflu-oroborates4, and with azulene11 to form aryl tellurium cyanides. 

Tellurocyanates converted tertiary phosphanes to phosphane tellurides1,2. The equilibrium constant for this reaction varies with the nature of the groups bonded to phosphorus2. 

Bis[triphenylphosphane]iminium tellurocyanate converted pentacarbonyl(diphenylcarb-ene)tungsten to pentacarbonyl(tellurodiphenylketone)tungsten3. 

Dibenzyl ditellurium compounds were obtained as photo- and thermolabile crystals, when dibenzyl tellurocyanates were treated with hypophosphorous acid4. 

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