Pincerlike Cyclic Systems for Unraveling Fundamental Coinage Metal Redox Processes

Pincerlike cyclic ligands have overcome the high instability of transition metals in their higher oxidation states and have permitted the isolation of such species and the exhaustive study of their properties and reactivity. The formation and isolation of organometallic Cu-II and M-III (M-Cu, Ag, Au) complexes stabilized by NCPs, carbaporphyrins, carbaporphyrinoids, heterocalixarenes, and triaza macrocyclic ligands will be discussed in this chapter. The study of these complexes have led to the discovery of unprecedented reactivity and proved the plausibility of often invoked pathways in copper-catalyzed cross-coupling reactions. Aryl-M-III (M=Cu, Ag) stable species have been implicated as the key intermediate species that operate in coupling catalysis through two-electron redox cycles involving oxidative addition and reductive elimination fundamental steps.