Organotellurium-halogen compounds

As a soft element tellurium becomes involved in secondary bonding in many of its compounds and interesting self-assemblies are produced leading to supramolecular architectures. Tellurium is attractive because of its diversity of oxidation states and coordination numbers. 

Several structurally characterized organotellurium halides have been found to be associated in the solid state. For example, a-dimethyltellurium dichloride, Me2TeCl2, forms a polymeric array (Te-Cl 2.541 and 2.480 A Te- Cl 3.46 and 3.52 A) [482]. -Me2Tel2 is a self-organized polymer (Te-12.854-2.994 A, Te- -13.659-4.030 A) [483] whereas j5-Me2Tel2 is a ionic compound [Me3Te]+[MeTel4] with cation-anion secondary bond interactions (Te- - -I 3.84-3.400 A) [484]. 

4 Supramolecular Self-Assembly by Formation of Secondary Bonds 

Perfluoroethyltellurium trifluoride, C2F5Tep3 is associated into infinite chains (terminal Te-F 1.870, 1.874 A, bridging Te-F 2.190, 2.196 A, Te- - F 3.168 A). The self-organized structure of (C6F5)2TeCl2 is shown in 207 and that of the corresponding bromide in 208. 

Weak Te- -Cl bonds lead to intermolecular association of phenylazophe-nyltellurium chloride [493]. Phenoxatellurin-10,10-dichloride is a tetramer (Te-Cl 2.478, 2.576 A, Te - Cl 3.504, 3.368 A) [494] whereas the 10,10-diiodide is an iodine-bridged polymeric chain-like array (Te-I 2.941, 2.945 A, Te---I 3.739, 3.788 A) [495]. 

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Diorganyl tellnrides, which as shown in Section 3.1 are the primary products of several methods for the synthesis of organotellurium compounds, can easily be converted into the corresponding dihalides by the simple addition of halogens. 

The transformation of a carbon-tellurium bond into a carbon-halogen bond has been achieved in several types of organotellurium compound. 

This class of electrophilic organotellurium compounds is prepared by the controlled addition of a halogen to diorganoditellurides. For many years, naphthyltellurium iodide, prepared for the first time in 1959,78 was the only stable organotellurium halide known in the solid state. Those containing an ortho-group able to coordinate with tellurium can be isolated (Scheme 10).S 10,11 79... 

The transformation of a carbon-tellurium bond into a carbon-halogen bond can be performed with several types of organotellurium trihalide or diorganotellurium dihalide compounds, in which the organic group is an alkyl, an alkenyl or an aryl substituent. A variety of reaction conditions have been described to realize these transformations, which belong to three main types ... 

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