Pt(pop-BF2) as a photosensitizer in photocatalytic carbon-chlorine bond formation

Abstract

Palladium complexes perform regioselective C-H functionalizations, which are essential for many syntheses. We are interested in halogenation of C-H bonds using [(benzo[h]quinoline)PdII(μ-OAc)]2 catalysts. Bulk electrolysis expts. show that we can chlorinate C-H bonds using chloride and Pd catalysts, eliminating the need for harsh chlorinating agents. To improve the speed and energetic cost of C-H transformations we are exploring reactions with photooxidants. Electronically excited fluoroborated tetrakis(μ-pyrophosphito)diplatinate(II) (Pt(pop-BF2)) undergoes facile electron transfer reactions. Electrochem. (E°(PtII-PtII/PtIPtII) = 1.3 V vs. SCE in MeCN) and fluorescence data were used to calc. E°(*PtII-PtII/PtII-PtI) = 1.4 V vs. SCE, suggesting that electronically excited Pt(pop-BF2) can oxidize Pd catalysts. Absorbance spectra of the transiently reduced Pt complexes were recorded. Time-resolved laser expts. in the presence of Pd catalyst suggest that *Pt(pop-BF2) generates catalytically active Pd intermediates, making it a viable sensitizer for photocatalyic C-H functionalizations.

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