Chemical elements
  Tellurium
    Isotopes
    Energy
    Production
    Physical Properties
    Chemical Properties
    Physiological_Action
    Atomic Weight
    Alloys
    Detection
    Estimation
    Compounds
      Hydrogen Telluride
      Tellurium Tetrafluoride
      Tellurium Hexafluoride
      Tellurium Oxyfluorides
      Tellurium Dichloride
      Tellurium Tetrachloride
      Tellurium Perchlorate
      Tellurium Dibromide
      Tellurium Tetrabromide
      Tellurium Oxybromides
      Tellurium Tetra-iodide
      Tellurium Monoxide
      Tellurium Dioxide
      Tellurites
      Tellurium Trioxide
      Telluric Acids
      Tellurates
      Tellurium Disulphide
      Tellurium-Sulphur Sesquioxide
      Tellurium Sulphates
      Telluropentathionic Acid
      Tellurium Nitride
      Tellurium Nitrite
      Basic Tellurium Nitrate
      Carbon Sulphidotelluride
      Tellurium Dicyanide
    Application
    PDB 1el7-4fon

Tellurium Dichloride, TeCl2






Tellurium Dichloride, TeCl2 is the first product of the regulated action of chlorine on tellurium, but it is difficult to prevent further conversion into the tetrachloride. A more satisfactory procedure is to boil tellurium tetrachloride with tellurium under reflux:

TeCl4 + Te = 2TeCl2.

When powdered tellurium is heated in a stream of carbonyl chloride, brown vapours of the dichloride are evolved, which may be condensed to a velvety-black crystalline mass.

When in a state of fine division, tellurium dichloride has a yellowish- green colour. On account of its miscibility with tellurium the chloride is difficult to obtain pure and the recorded melting-points range from 209° to 175° C.; the boiling-point is near 324° C. The reddish vapour at 450° C. has a density in keeping with the unimolecular formula TeCl2.

Bivalent tellurium is not stable and the dichloride in the solid state tends to undergo self-oxidation and reduction, forming a solid solution of the element in the tetrachloride. Under the action of water, acids or alkalis, tellurium and tellurous acid are formed:

2TeCl2 + 3H2O = Te + H2TeO3 + 4HCl.

The dichloride is stable only in the gaseous condition or in solution when in equilibrium with its decomposition products. It is hygroscopic, but does not fume in air. When heated in air it burns to tellurium dioxide and tetrachloride. It is also slowly converted by chlorine into the tetrachloride.

Repeated sublimation of tellurium dichloride with a deficiency of ammonium chloride leads to the formation of a greenish-black chlorotellurite, (NH4)2TeCl4, which is stable in air and not hygroscopic.

The dichloride reacts with magnesium phenyl bromide, C6H5.MgBr, in ether solution, with formation of diphenyl telluride, (C6H5)2Te. Tellurium dibromide and di-iodide give a similar result. In ether solution the dichloride absorbs bromine and iodine, but the products, presumably the chlorobromide and chloro-iodide, respectively, have not been isolated.


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