Tellurium -chloride TeCl

Triethyl tellurium chloride,2 (CgHg TeCl, is isolated when an ether solution of tellurium tetrachloride is added dropwise to a similar solution of zinc diethyl. It crystallises from alcohol as colourless plates, M.pt. 174° C., readily soluble in alcohol, sparingly soluble in ether. It is deliquescent in air, and with moist silver oxide gives a hydroxide. 

Di-o-tolyl methyl tellurium chloride,2 (C7H7)2(CH3)TeCl, is obtained by boiling the corresponding iodide with silver chloride and water. It separates from water as four-sided plates containing two molecules of water of crystallisation, melting at 93° C. and again at 148° C. from chloroform it crystallises with half a molecule of chloroform, and melts at 155° to 156° C. The basic zinc chloride double salt melts with decomposition at 186° to 187° C. 

Tellurium Halides. Tellurium forms the dihalides TeCl and TeBi, but not Tel2. However, it forms tetrahalides with all four halogens. Tellurium decafluoride [53214-07-6] and hexafluoride can also be prepared. No monohalide, Te2X2, is believed to exist. Tellurium does not form well-defined oxyhalides as do sulfur and selenium. The tellurium halides show varying tendencies to form complexes and addition compounds with nitrogen compounds such as ammonia, pyridine, simple and substituted thioureas and anilines, and ethylenediamine, as well as sulfur trioxide and the chlorides of other elements. 

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). 

Volumetrically tellurium may be determined by several methods (1) Tellurous acid is oxidized to telluric by permanganate either in acid solution 3 or alkaline solution.4 (2) Tellurous acid in hydrochloric acid solution is reduced by an excess of standard stannous chloride, according to the reaction TeCl< + 2 SnCU — Te + 2 SnCL. The excess stannous chloride is determined iodometrically.5 (3) Telluric acid may be reduced to tellurous by the use of potassium bromide in sulfuric acid solution, thus H2TeO< + 2 HBr = H2TeO + H20 + Br2. The bromine is distilled into a solution of potassium iodide, the liberated iodine being determined by standard thiosulfate.6... 

The solvated entities Te ", Teo, and Tel have been identified in reaction mixtures of dilute solutions of TeCU and elemental tellurium in the low-melting NaCl-AlCl3(37 63 mol%) solvent at 250 The enthalpy of formation of the complex ion TeCl " has been determined as AHf=-1020.4 kJmorS and the affinity of gaseous TeCU for chloride ion to be -304.1 kJ mor ... 

Sulfur and selenium diamides are obtained by the reaction of sulfur or selenium chlorides with an aliphatic secondary amine. Polyselanes Se,c(NR2)2 ( = 2-4, NR2=morpholinyl x = 4, NR2=piperidinyl) are formed in the reaction of elemental selenium with the boiling amine in the presence of Pb304. The acyclic tellurium(II) diamide [Te(NMe2)2]oo (see Figure 1) is prepared by the reaction of TeCL with LiNMc2. ... 

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