Aerobic Photooxidation and C-C Bond Cleavage of the Acetylacetonate Ligand in (2-Arylazo)arylpalladium(II) Complexes Induced by Visible Light

Article abstract of DOI:10.1039/DT9940001505

(Arylazo)aryl(acetylacetonato)palladium(II) complexes, (R = H 1a, Me 1b or OMe 1c; Hacac = acetylacetone), upon irradiation of their acetone solutions at room temperature by UV, or even long-wavelength visible (λ > 500 nm) light, were readily oxidized by atmospheric oxygen to give the corresponding acetato derivatives 2 (R = H 2a, Me 2b or OMe 2c), providing a model for some chemical and biological processes.The oxidation reaction of complex 1b was first order in the complex <1b>₀ -3.Complexes 1b and 1c were photooxidized at approximately twice the rate of complex 1a.In the presence of a scavenger of C-centred radicals (CCl4) the rate of complex 2b accumulation was reduced.When pyridine was added or co-ordinating solvents (acetonitrile or nitromethane) were used no photooxidation of comlex 1 occured.In the presence of PPh3 an induction period was observed and the oxidation of 1 strted only after all the PPh3 was oxidized under irradiation into OPPh3.Spectroscopic data suggested that these ligands inhibit this photochemical oxidation because they change the type of co-ordination of the azobenzene chromophore and/or the acac ligands inducing a disconnection between the chromophore (antenna) and the acac ligand.

Full text of DOI:10.1039/DT9940001505

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