P,N Ligand in Ni-Catalyzed Cross-Coupling Reactions: A Promising Tool for π-Functionalization

Abstract

Bidentate P,N ligands, integrating phosphine and nitrogen donors, are highlighted for their versatile characteristics, offering both electronic and steric tunability. Their hemilabile nature, coupled with the ability to modulate both electronic and steric properties through the choice of donor atoms and substituents, has expanded the horizons of chemical transformations. This Review focuses on Nicatalyzed cross-coupling reactions mediated by P,N ligands. The asymmetrical nature of P,N ligands, with each donor atom playing a specific role in the catalytic cycle, offers control, stability, and unique regioselectivity in catalytic processes. In particular, the Ni/P,N-catalytic system exhibits remarkable reactivity with πsubstrates including alkenes, alkynes, and allenes. A thorough mechanistic understanding of these processes offers insights into the trends and future directions in Ni/P,N-catalyzed cross-coupling reactions.

Ni-catalyzed regioselective C–C bond formation of 1,1-disubstituted allenes with aldehydes

“…4 In a distinctive photoredox/Ni-dual catalysis approach by the Breit group, the selective formation of the branched coupling product was achieved through the initial formation of a π-allyl Ni intermediate in the presence of a base. 5–8 Subsequently, this intermediate underwent nucleophilic addition to the aldehyde via the Zimmerman–Traxler transition state (Scheme 1a-ii).…”

Enantioselective Directed Nickel-Catalyzed Three-Component Reductive Arylalkylation of Alkenes via the Carbometalation/Radical Cross-Coupling Sequence

“…The intermediate D performed facile reductive elimination to give the final product and release L*Ni­(I) E . Finally, the species L*Ni­(II) F was reduced by Mn to regenerate the catalytically active L*Ni 0 ( A ) complex. ,− …”

Isolation and Reactivity of Arylnickel(II) Complexes in Nickel-Catalyzed Borylation of Aryl Fluorosulfates

“…Organoborons have gained recognition as key organometallic reagents owing to their synthetic versatility, bench stability, low toxicity, and ease of handling. − Recent progress in palladium-catalyzed C–B bond formation, including the Miyaura borylation of aryl halides, has paved the way for the establishment of straightforward and reliable routes to prepare arylboron compounds. − However, comparatively less attention has been focused on elucidating the reaction pathways in nickel-catalyzed processes. , Nickel catalysts, in addition to being cost-effective, exhibit superior performance compared to palladium ones in activating less reactive electrophiles such as pseudohalides, esters, or even ethers. , Despite these advantages, nickel can exist in diverse oxidation states, and the facile interconversion between these states can pose challenges in controlling the desired reactivity. − Furthermore, the requirement of relatively high catalyst loading limits the practical application of nickel catalysis. Therefore, gaining a comprehensive understanding of the reaction mechanism, especially when it involves the activation of C–O bonds, is crucial.…”

“… 13 , 14 Despite these advantages, nickel can exist in diverse oxidation states, and the facile interconversion between these states can pose challenges in controlling the desired reactivity. 15 − 19 Furthermore, the requirement of relatively high catalyst loading limits the practical application of nickel catalysis. Therefore, gaining a comprehensive understanding of the reaction mechanism, especially when it involves the activation of C–O bonds, is crucial.…”