Photochemical reactions between tertiary phosphines and organic diselenides

Abstract

Tertiary phosphines, PR¹₃, react with organic diselenides, Se₂R²₂, under u.v. radiation to produce PR¹₃Se and SeR²₂. The reaction rates decrease in the orders R¹₃, = Me₂Ph > MePh₂ > Ph₃ and R²= CH₂Ph > Et > Me > Ph. A radical-chain mechanism appears to operate via SeR2˙ and PR¹₃(SeR²)˙. Although cleavage of Se–C bonds may be involved in the u.v. irradiation of Se₂R²₂, cleavage of Se–Se bonds seems more important in these reactions, even for R²= CH₂Ph.