Photolysis of diorganoditellurides in the presence of tertiary phosphines

Abstract

Ultraviolet irradiation of solutions of R 2Te 2 (R = Et or PhCH 2) produces R 2Te and Te quantitatively. In the presence of teretiary phosphines, R′ 3P[R′ 3 = Ph 2Me or Ph 2(CH 2PPh 2)], the reactions are accelerated via the formation of R′ 3PTe, which decomposes to liberate Te and reform R′ 3P. A rapid (on the NMR) timescale) equilibrium between R′ 3PTe and R′ 3P + Te is established in solution. All the reactions can satisfactorily be interpreted in terms of an initiation step involving photochemical cleavage of TeC bonds. Comparisons with analogous reactions of R 2S 2 and R 2Se 2 suggest that elementcarbon bonds are more easily cleaved by UV radiation as the group is descended, whereas elementelement bond cleavage becomes less important.