Photolysis of diorganoditellurides in the presence of tertiary phosphines

Ultraviolet irradiation of solutions of R2Te2 (R = Et or PhCH2) produces R2Te and Te quantitatively. In the presence of teretiary phosphines, R′3P[R′3 = Ph2Me or Ph2(CH2PPh2)], 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 R2S2 and R2Se2 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.