Palladium-Borane Cooperation: Evidence for an Anionic Pathway and Its Application to Catalytic Hydro-/Deutero-dechlorination

Metal-Lewis acid cooperation provides new opportunities in catalysis. In this work, we report a new type of palladium-borane cooperation involving anionic Pd-0 species. The air-stable DPB palladium complex 1 (DPB=diphosphine-borane) was prepared and reacted with KH to give the Pd-0 borohydride 2, the first monomeric anionic Pd-0 species to be structurally characterized. The boron moiety acts as an acceptor towards Pd in 1 via Pd -> B interaction, but as a donor in 2 thanks to B-H-Pd bridging. This enables the activation of C-Cl bonds and the system is amenable to catalysis, as demonstrated by the hydro-/deutero-dehalogenation of a variety of (hetero)aryl chlorides (20 examples, average yield 85 %).