Organic Derivatives of Tellurium

ORGANIC DERIVATIVES OF TELLURIUM The dialkyl tellurides are prepared by distilling potassium tel luride with the salts of alkyl sulphuric acids. Dimethyl telluride, a liquid of repulsive odour, boils at 82° C. It is probably the origin of the unpleasant garlic odour noticed in the breath and perspiration of patients or animals treated with tellurium or tellurium compounds. Diethyl telluride, the proposed anti-knock compound, boils at 1375° C. When heated together at 8o° tel lurium and methyl iodide combine to form red dimethyltel luronium di-iodide, (CH3)2TeI2, converted by silver oxide into dimethyltelluronium dihydroxide, a base which on heating yields the complex oxide :0. This oxide forms two iodides, and which unite together yielding greenish-black spangles of the complex iodide [TeCH3I4] (H. D. K. Drew, 1929).

By the action of tellurium tetrachloride on acetylacetone and certain of its homologues, a series of cyclic organotellurium com pounds have been obtained containing the cyclotelluropentane ring. The initial product, cyc/otelluropentane-3 :5-dione dichlo ride, m.p. 115° C (formula I.), is reduced by alkali bisulphites to cyclotelluropentane-3 :5-dione (II.) crystallising in golden yellow needles and melting at 182° C (G. T. Morgan and H. D. K. Drew, 1920-1922). The substance and its homologues have outstanding bactericidal properties, even in extremely dilute solutions.

The condensation of aluminium telluride with pentamethylene ae-dibromide gives rise to three cyclic tellurium compounds from which cyclotelluropentane (formula III.) can be prepared. This compound, the parent substance of the ketonic series (II.) is a

very oxidisable yellow oil (b.p. 82-83712 mm.) with disagreeable odour, and gives rise to crystalline dihalides, (G. T. Morgan and H. Burgess, 1928). When tellurium tetrachloride reacts with acetic anhydride, the product furnishes tellurodia cetic and ditellurodiacetic acids, together with a compound, CH2(TeC13)2, containing no oxygen. This hexachloride on reduc tion with bisulphite loses all its chlorine and yields ditellurome thane (CH2:Te2), a solid existing in red and black modifications (Morgan and Drew, 1925).

Detection and Estimation.

Tellurium is precipitated by hydrogen sulphide and is separated from selenium owing to the greater facility with which the latter is liberated from its com pounds by reducing agents. In strongly acid solutions sulphur dioxide eliminates red selenium but not tellurium. The excess of acid and sulphur dioxide are boiled off; potassium iodide is added. and black is precipitated, redissolving in excess of reagent to from which dark red solution sulphur dioxide now readily precipitates tellurium. Tellurium may be weighed either as such or as the oxide.

Abegg, F. Auerbach and I. Koppel, Handbuch der Anorganischen Chemie, Vol. IV. (Leipzig, 1927), with a chapter on the colloid chemistry of tellurium; B. S. Hopkins, Chemistry of the Rarer Elements (New York, 1923) ; G. A. Roush, The Mineral In dustry (New York, 1916 and annually), containing an epitome of the industrial development of tellurium in the U.S.A. (G. T. M.)