Phosphino(silyl) Nickel Complexes for Alkene Hydroboration Catalysis: Steric Tuning of Pre‐Catalyst Provides High Regioselectivity

Abstract Bis(phosphino)silyl nickel complexes featuring diethylphosphino donors on the tridentate PSiP ligand are effective pre‐catalysts for room temperature alkene hydroboration with HBPin. Terminal and geminal alkenes, including a wide scope of vinyl arenes, reacted to afford exclusively the linear, anti‐Markovnikov boronate ester product in all cases. Internal alkene substrates undergo Ni‐mediated tandem alkene isomerization‐hydroboration to afford the terminal borylation products with high selectivity. Deuterium labeling studies employing DBPin support a Ni‐H‐based mechanism for this reactivity, whereby alkene isomerization occurs via reversible alkene insertion/β‐hydride elimination steps. We propose that steric tuning of the PSiP ligand influences the observed regioselectivity.