Catalysis with Palladium(I) Dimers

Dinuclear Pd(I) complexes have found widespread applications as diverse catalysts for a multitude of transformations. Initially their ability to function as pre‐catalysts for low‐coordinated Pd(0) species was harnessed in cross‐coupling. Such Pd(I) dimers are inherently labile and relatively sensitive to oxygen. In recent years, more stable dinuclear Pd(I)−Pd(I) frameworks, which feature bench‐stability and robustness towards nucleophiles as well as recoverability in reactions, were explored and shown to trigger privileged reactivities via dinuclear catalysis. This includes the predictable and substrate‐independent, selective C−C and C−heteroatom bond formations of poly(pseudo)halogenated arenes as well as couplings of arenes with relatively weak nucleophiles, which would not engage in Pd(0)/Pd(II) catalysis. This Minireview highlights the use of dinuclear Pd(I) complexes as both pre‐catalysts for the formation of highly active Pd(0) and Pd(II)−H species as well as direct dinuclear catalysts. Focus is set on the mechanistic intricacies, the speciation and the impacts on reactivity.