Photoinduced oxidative degradation of unsaturated M3(dppm)3CO2+ clusters (M = Pd, Pt) by chlorocarbons and chloride ion

Article abstract of DOI:10.1139/v96-255

Both M₃(dppm)₃CO²⁺ clusters (M = Pd, Pt) photoreact with chlorocarbons (Cl-R; R = CCl₃, CHCl₂, CH₂Cl, C₆H₅, C₁₀H₁₅ (adamantyl)) and chloride ion (slowly) to produce the oxidized mononuclear species M(dppm)Cl₂ as a sole isolated M-coordinated inorganic product. Such reactions do not proceed in the dark, except for R = CH₂C₆H₅. Among the organic products, the coupling compound R-R (R = C₆H₅) is observed along with many phosphine compounds such as P(C₆H₅)₃. In an attempt to elucidate the photoinduced mechanism at the early stage of the phototransformations, the following have been investigated : the ground state binding constants (K₁₁ for M = Pd in methanol), the photochemical quantum yields of cluster disappearance (Φ_dis for M = Pd) as a function of substrates, substrate concentrations, excitation wavelengths, solvents (ethanol vs toluene), and presence of CO, and the emission lifetimes (τ_e for M = Pt) at 77 K as a function of substrate concentrations (CH₂Cl₂ and CHCl₃) in ethanol and toluene. Some of the experimental conclusions have also been corroborated theoretically using density functional theory. Geometry optimization calculations have been performed for the model compounds Pd₃(PH₃)₆CO²⁺...Cl^-, Pd₃(PH₃)₆²⁺, Pd₃(PH₃)₆CO²⁺...Cl⁰, Pd₃(PH₃)₆CO²⁺...Cl-CH ₃, and Pd₃(PH₃)₆CO³⁺in their ground states.