High-Valent Platinum Complexes

High Selectivity in Csp2–Csp2 versus Csp3–O Reductive Elimination from Cycloplatinated(IV) Complexes

“…Transition metal-catalyzed selective C–H functionalization of hydrocarbons is one of the major challenges of organometallic chemistry. − This transformation involves a number of fundamental steps such as oxidative addition (OA), β-hydride elimination, migratory insertion, and reductive elimination (RE). ,, RE reactions are critical for the final product-forming step. − To reduce deleterious side reactions and enhance overall catalyst efficiency, the metal must undergo the appropriate series of fundamental reactions with great selectivity . Understanding the parameters that influence the selectivity of these reactions is key to designing and improving novel transition metal-catalyzed transformations. − High-valency octahedral metal complexes have more donor ligands at the metal center than their more common square planar counterparts, which may indicate greater competitiveness in the formation of C–C or C–X (X = heteroatom such as O, N, and S) bonds and thus require greater control over the reaction selectivity. , For instance, as different research groups have reported, competitive carbon–carbon and/or carbon–heteroatom bond RE can be seen at Pt­(IV) and Pd­(IV) centers in a single complex. ,− Notably, high-valency d 6 metal systems typically prefer the C–C over the C–X coupling reaction, though exceptions to this trend have been noted. ,− On the other hand, the formation of new C–C or C–X (X = heteroatom) bonds through RE from a M­(IV) center (group 10) constitutes the product-forming step in various catalytic oxidative transformations that have garnered considerable attention over the past 2 decades. ,− Despite some noteworthy advancements in this field, mechanistic studies in selective C–X vs C–C bond RE reactivity have not been extensively investigated. ,, Furthermore, the chemoselectivity of C–X bond RE is poorly known in systems where different competing coupling reactions may occur . As a result of their kinetic inertness, Pt­(IV) compounds can be considered excellent models for studying these coupling processes. ,,…”