A detailed study of acetate-assisted C-H activation at palladium(IV) centers.

This report describes a detailed investigation of acetate-assisted C-H activation at Pd(IV) centers supported by the tris(2-pyridyl)methane (Py3CH) ligand. Mechanistic information about this transformation has been obtained through the following: (i) extensive one- and two-dimensional NMR analysis, (ii) reactivity studies of a series of substituted analogues, and (iii) isotope effect studies. These experiments all suggest that C-H activation at [(Py3CH)Pd(IV)(biphenyl)Cl2](+) occurs via a multistep process involving chloride-to-acetate ligand exchange followed by conformational and configurational isomerization and then C-H cleavage. The data also suggest that C-H cleavage proceeds via an acetate-assisted mechanism with the carboxylate likely serving as an intramolecular base. The viability of acetate-assisted C-H activation at high valent palladium has important implications for the design and optimization of catalytic processes involving this transformation as a key step.