and selenenyl chloride could be produced through the following synthetic routes.

A. Diphenyl diselenide (CAS NO.: ). A 2-l., three-necked, round-bottomed flask is equipped with a mechanical stirrer, a pressure-equalizing dropping funnel, and an efficient reflux condenser mounted with a combined inlet-outlet assembly connected to a nitrogen source and a bubbler. The apparatus is flamed dry while a slow stream of nitrogen is passed through the system. In the cooled flask a solution of phenylmagnesium bromide is prepared from 160 g. (1.02 mole) of bromobenzene, 24.0 g. (0.988 g.-atom) of magnesium, and 550 ml. of anhydrous diethyl ether. The dropping funnel is removed, and an Erlenmeyer flask containing 70 g. (0.89 g.-atom) of selenium is attached to the neck of the flask with a section of nylon tubing. The selenium is added in portions at a rate sufficient to maintain a vigorous reflux. The addition requires 15–30 minutes, after which the mixture is stirred and heated at reflux for another 30 minutes. The Erlenmeyer flask and nylon tubing are removed, and 3 g. (0.2 mole) of water is added to hydrolyze any excess Grignard reagent. The mixture is stirred and cooled in an ice bath while 74.3 g. (23.8 ml., 0.465 mole) of bromine is added dropwise at a rate such that the ether does not reflux. Cooling and stirring are continued as a solution of 53.5 g. (1.00 mole) of ammonium chloride in 140 ml. of water is added slowly. The mixture is filtered by gravity into a 1-l., round-bottomed flask, and the granular precipitate is washed thoroughly with three 100-ml. portions of ether. The combined filtrates are evaporated, the remaining solid is dissolved insofar as possible in 500 ml. of hot hexane, and a small amount of insoluble material is separated by gravity filtration. The filtrate is allowed to crystallize at room temperature and then at 6°. The yellow microcrystalline solid is collected, washed with 30 ml. of pentane, and dried in the air, 89–97 g. (64–70%) of diphenyl diselenide, m.p. 60–62°.

B. Benzeneselenenyl chloride (CAS NO.: ). A 1-l., three-necked, round-bottomed flask equipped with a magnetic stirring bar, a thermometer, a gas-inlet tube, and a reflux condenser is charged with 50 g. (0.16 mole) of diphenyl diselenide and 350 ml. of hexane. The mixture is warmed to 40–50°, dissolving the solid. The resulting solution is stirred while chlorine gas is passed through the gas-inlet tube into the flask 1 cm. above the surface of the liquid, at a rate sufficient to maintain the temperature between 40° and 50°. Chlorination is continued until 11.3 g. (0.159 mole) of the gas is absorbed. The solution is heated to reflux, filtered by gravity, and allowed to cool slowly at room temperature, then at 6°. The mother liquor is decanted, the large, deep-orange crystals are washed with 25 ml. of pentane, and the residual solvent is evaporated by passing a slow stream of nitrogen over the crystals for 30 minutes, giving 51–54 g. (84–88%) of benzeneselenenyl chloride, m.p. 60–62°.

Notice: Most selenium compounds are toxic; care should be exercised to avoid contact with skin. All operations in this procedure should be conducted in a well-ventilated hood.