Catalysis with Palladium(I) Dimers

Dinuclear PdI complexes have found widespread applications as diverse catalysts for a multitude of transformations. Initially their ability to function as pre‐catalysts for low‐coordinated Pd0 species was harnessed in cross‐coupling. Such PdI dimers are inherently labile and relatively sensitive to oxygen. In recent years, more stable dinuclear PdI−PdI 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 Pd0/PdII catalysis. This Minireview highlights the use of dinuclear PdI complexes as both pre‐catalysts for the formation of highly active Pd0 and PdII−H species as well as direct dinuclear catalysts. Focus is set on the mechanistic intricacies, the speciation and the impacts on reactivity. While dinuclear PdI complexes first received attention for being excellent pre‐catalysts that lead to high cross‐coupling reactivities, more recent work has uncovered that direct dinuclear catalysis can also take place and reaction modes are accessible which are not amenable to Pd0/PdII cycles. This Minireview highlights the use of dinuclear PdI complexes in catalysis showcasing their unique reactivity and selectivity.