Unexpected Nickel Complex Speciation Unlocks Alternative Pathways for the Reactions of Alkyl Halides with dppf-Nickel(0)

The mechanism of the reactions between dppf-Ni0 complexes and alkyl halides has been investigated using kinetic and mechanistic experiments and DFT calculations. The active species is [Ni(dppf)2], which undergoes a halide abstraction reaction with alkyl halides and rapidly captures the alkyl radical that is formed. The yields in prototypical nickel-catalysed Kumada cross-coupling reactions are shown to be improved by the addition of free phosphine ligands