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

Both M(3)(dppm)(3)CO2+ 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)Cl-2 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 (K-11 for M = Pd in methanol), the photochemical quantum fields of cluster disappearance (Phi(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 (tau(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 Pd-3(PH3)(6)CO2+... Cl-, Pd-3(PH3)(6)(2+), Pd-3(PH3)(6)CO2+... Cl-0, Pd-3(PH3)(6)CO2+... Cl-CH3, and Pd-3(PH3)(6)CO3+ in their ground slates.