Photolysis of Pincer-Ligated PdII-Me Complexes in the Presence of Molecular Oxygen

The reactions of t-BuPNP and t-BuPCP Pd-II-Me complexes (t-BuPNP = 2,6-bis[(di-tert-butylphosphino)methyl]pyridine and t-BuPCP = 2,6-bis[(di-tert-butylphosphino)methyl]phenyl) with O-2 are described and compared with the reported O-2 reactivity of related Pd-II-Me complexes. [(t-BuPNP)PdMe] Cl was found to react with O-2 upon photolysis resulting in oxidation of the pincer ligand backbone to produce a (t-BuPNO)PdCl complex. In contrast, photolysis of (t-BuPCP)PdMe with O-2 resulted in oxidation of the Pd-Me group to form (t-BuPCP)PdOCO2H. Isotopic labeling, radical initiators, and solvent studies were used to gain insight into the mechanisms of these unusual reactions of late metal alkyls with molecular oxygen.