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

Abstract

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 (Φdis for M = Pd) as a function of substrates, substrate concentrations, excitation wavelengths, solvents (ethanol vs toluene), and presence of CO, and the emission lifetimes (τe 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 [Formula: see text] Pd3(PH3)62+,[Formula: see text], [Formula: see text] and Pd3(PH3)6CO3+ in their ground states. Key words: atom abstraction, photochemistry, C-Cl bond, clusters, host-guest.