Photochemistry of diplatinum(III,III) pyrophosphite complexes. Efficient photochemical reduction of [Pt2(pop)4X2]4- to [Pt2(pop)4]4- in methanol

Abstract

UV-vis irradiation of [Pt2(pop)4X2]4- [pop = P2O5H2 2-; X = Cl, Br, SCN, I, Im (ImH = imidazole)] in methanol leads to reduction to [Pt2(pop)4]4- with nearly quantitative yield (over 92%). Upon ligand-to-metal charge-transfer [σx → dσ*] excitation, the quantum yield (φr) for the reduction of [Pt2(pop)4X2]4- decreases with X2 = (CH3)(I) 〉 (SCN)2 〉 I2 〉 Im2 〉 Cl2 〉 Br2. The φr values are wavelength dependent, being higher with σx → dσ* excitation than that with dπ → dσ*. Flash photolysis experiments indicate that the primary step of the photoreactions is the homolytic breakage of the Pt-X bond, [Pt2(pop)4X2]4- → [PtIIIPtIII(pop)4X]4- + •X. © 1988 American Chemical Society.