When using platinum as a catalyst for C-H activation and functionalization reactions, cis and trans isomers may have different activity. The configuration may have an effect on oxidative addition, ligand exchange, and reductive elimination. During the course of investigating the platinum-catalyzed C-H acylation reaction of 2-aryloxypyridines, the Huo lab observed that the cis-Pt(PhCN)2Cl2-catalyzed C-H acylation was faster in comparison to using trans-Pt(PhCN)2Cl2 as the catalyst. To further understand this difference in catalytic activity, we carried out a comparative study in the catalytic activity of the two isomeric platinum benzonitrile complexes and other potential intermediate platinum complexes in the catalytic reaction. We chose 2-(2-Methylphenyl)pyridine (L) as the model substrate for the investigation because the presence of the methyl group provides a convenient way to monitor the reaction and quantify the product formation through analyzing the proton NMR spectra of the crude reaction mixture. It was determined that all cis platinum complexes exhibited higher catalytic activity in comparison to their corresponding trans isomers, especially at the initial stage of the reaction. This trend was correlated to the faster ligand exchange and C-H activation/cycloplatination that is exhibited by the cis isomer.

Configuration-dependent difference in catalytic activity of isomeric platinum complexes in catalytic C-H acylation reaction

ACS Fall 2021

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