A Highly Efficient and Selective Aerobic Cross-Dehydrogenative-Coupling Reaction Photocatalyzed by a Platinum(II) Terpyridyl Complex

Thanks to the superior redox potential of platinum(II) complex compared with that of Ru(bpy)32+ in the excited state, an efficient and selective visible-light-induced CDC reaction has been developed by using a catalytic amount (0.25%) of 1. With the aid of FeSO4 (2equiv), the corresponding amide could not be detected under visible-light irradiation (=450nm), but the desired cross-coupling product was exclusively obtained under ambient air conditions. A spectroscopic study and product analysis revealed that the CDC reaction is initiated by photoinduced electron-transfer from N-phenyltetrahydroisoquinoline to the complex. An EPR (electron paramagnetic resonance) experiment provides direct evidence on the generation of superoxide radical anion (O2.) rather than singlet oxygen (1O2) under irradiation of the reaction system, in contrast to that reported in the literature. Combined, the photoinduced electron-transfer and subsequent formation of superoxide radical anion (O2.) results in a clean and facile transformation.