Alkylpalladium N-Heterocyclic Carbene Complexes: Synthesis, Reactivity, and Catalytic Properties

The dimers [trans-[(neopentyl)Pd(mu-Cl)(I(t)lBu)](2), 2, and (cis-[(neopentyl)Pd(mu-Cl)(IPr)](2), 3 ((IBu)-Bu-t = 1,3-bis-tert-butylimidazol-2-ylidene, IPr = 1,3-bis-2,6-diidopropylimidazol-2-ylidene), have been synthesized from [Pd(neopentyl)(Cl)(1,5-COD)], and their reactivity toward a variety of nucleophiles has been evaluated. In particular, this study revealed that 2 can be readily cleaved by primary and secondary amines, affording stable transamination products, which are surprisingly resistant to deprotonation. Dimer 3 was subsequently used as a catalyst in a series of Buchwald-Hartwig amination reactions of aryl chlorides.