Sodium Diselenide1

Na2Se2

[39775-49-0]  · Na2Se2  · Sodium Diselenide  · (MW 203.90)

(nucleophilic agent for synthesis of organic diselenides1,2)

Alternate Name: disodium diselenide.

Physical Data: mp about 495 °C.

Solubility: readily sol water, forming a red solution which easily decomposes on contact with air, separating selenium; sol ethanol, liquid ammonia; sparingly sol THF.

Form Supplied in: dull gray-black, microcrystalline material; used in solution or suspension without isolation.

Preparative Methods: heat equimolar amounts of Sodium and Selenium under nitrogen at 500 °C, or reduce Se with Na in liquid ammonia.4 Sodium Hydroxymethanesulfinate (rongalite) in water5 and Sodium Borohydride in water or ethanol6 are used as reducing agents. Hydrazine in aqueous alkali also reduces Se, giving Na2Se2 or K2Se2 solutions as a source of Se22-.7,8 A combination of electrochemical reduction of Se and ultrasound will produce the Se22- anion in THF, acetonitrile, or DMF.9 A suspension of Na2Se2 (or K2Se2) can be produced in high-boiling polar aprotic solvents, such as DMF, HMPA, or NMP by the direct reaction of selenium powder with sodium or Potassium.10 A similar reduction in THF, carried out in the presence of catalytic amounts of naphthalene, is the best way to prepare of a suspension of Na2Se2 or K2Se2 in this solvent.2

Handling, Storage, and Precautions: very hygroscopic; decomposes in moist air, turning red. It should be used as prepared without isolation. Use in a fume hood.

Synthesis of Diselenides.

The diselenide anion Se22- derived from Na2Se2 or K2Se2 is an excellent nucleophilic agent used for the synthesis of dialkyl diselenides from alkyl halides or sulfates.2,4-8,11 The alkylating agent is added directly to the alkali metal diselenide solution or suspension and the dialkyl diselenide is formed, usually in high yield (eq 1).2 Nucleophilic aromatic substitution with the Se22- anion is achieved on activated aromatic halides, such as 2-nitrochlorobenzene (eq 2).12


1. Paulmier, C. Selenium Reagents and Intermediates in Organic Synthesis; Pergamon: Oxford, 1986.
2. Thompson, D. P.; Boudjouk, P. JOC 1988, 53, 2109.
3. Feher, F. In Handbook of Preparative Inorganic Chemistry; Brauer, G. Ed.; Academic: New York, 1963; Vol. 2, p 421.
4. Brandsma, L.; Wijers, H. E. RTC 1963, 82, 68.
5. Bird, M. L.; Challenger, F. JCS 1942, 570.
6. Klayman, D. L.; Griffin, T. S. JACS 1973, 95, 197.
7. Syper, L.; Mlochowski, J. S 1984, 439.
8. (a) Korchevin, N. A.; Podkuiko, P. A.; Stankevich, V. K.; Deryagina, E. N.; Voronkov, M. G. ZOB 1989, 59, 1788. (b) Jakiwczyk, O. M.; Kristoff, E. M.; McPhee, D. J. SC 1993, 23, 195.
9. Sandman, D. J.; Stark, J. C.; Acampora, L. A.; Gagne, P. OM 1983, 2, 549.
10. Gautheron, B.; Tainturier, G.; Degrand, C. JACS 1985, 107, 5579.
11. (a) Backer, H. J.; van Dam, W. RTC 1930, 49, 479. (b) Rebane, E. AK 1966, 25, 363.
12. (a) Bogert, M. T.; Stull, A. JACS 1927, 49, 2011. (b) Battistoni, P.; Bompadre, S.; Bruni, P.; Fava, G. G 1981, 111, 505. (c) Rheinboldt, H. MOC 1955, 9, 993.

Jacek Mlochowski & Ludwik Syper

Technical University of Wroclaw, Poland



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