Ligand-enabled PtII–C(sp3) bond functionalization with dioxygen as a direct oxidant

Abstract

This feature article summarizes the progress achieved in the field of aerobic functionalization of Pt^II monoalkyl complexes in protic solvents, water and alcohols. These functionalization reactions are possible in the presence of tripodal semi-labile ligands such as di(2-pyridyl)methanesulfonate (dpms). The reactions include two subsequent transformations: (i) direct (mediatorless) oxidation of a Pt^II monoalkyl or a Pt^II-oxetane to produce a Pt^IV(OH) alkyl or a Pt^IV(OH)-oxetane, respectively, and (ii) reductive elimination from the Pt^IV center of an oxygenated organic derivative with a new C–O bond such as alcohols (MeOH, HOC₂H₄OH), ethers (Me₂O), or olefin (ethylene, cis-cyclooctene, norbornene) oxides. All the reactions are highly chemo- and stereoselective. Mechanisms of dioxygen activation with (dpms)Pt^II alkyls and C–O reductive eliminations from a Pt^IV center are discussed, including the direct C–O elimination of epoxides from Pt^IV oxetanes previously undocumented for this metal. Modification of the “slow” Pt^II-based systems led to the discovery of a “fast” dioxygenase-like acetoxylation of benzylic C–H bonds catalyzed by homogeneous Pd complexes with O₂ as the sole oxidant.