Preparation of the Principal Classes of Organic Tellurium Compounds

This chapter discusses diorganyl tellurides and ditellurides, organyltellurium trichlorides and diorganyltellurium dichlorides, which were the first classes of compounds investigated at the beginning of tellurium (Te) organic chemistry. Diorganyl tellurides, compounds with two organic groups linked to a Te atom, constitute the most abundant and familiar class of organic Te compounds. The organic groups of the most differentiated types can be identical or different, giving rise to symmetrical or unsymmetrical tellurides. The main routes to symmetrical diorganyl tellurides involve the direct reaction of nucleophilic telluride dianions with alkylating or arylating reagents. Otherwise, the electrophilic Te tetrahalides react with arylmagnesium reagents, giving diaryl tellurides. Diorganyl ditellurides are prepared by three routes: alkylation or arylation of the ditelluride dianion; oxidation of tellurolate anions; and reduction of the corresponding organyltellurium trichlorides. Organyltellurium trichlorides and diorganyltellurium dichlorides are prepared starting from the electrophilic tellurium tetrachloride by (1) condensation reactions with active methylene compounds; (2) addition to a C=C bond; (3) electrophilic substitution in aromatic hydrocarbons; and (4) reaction with organomercury chlorides. This chapter explores the preparation of principal classes of organic Te compounds in detail.