Ligand‐Facilitated Reductive Coupling of Benzyl Chlorides with Aryl Chlorides Catalyzed by Well‐Defined Heteroleptic Ni (II)‐NHC Complexes

Abstract

Novel heteroleptic Ni (II) complexes bearing a highly hindered yet flexible IPr* ligand, Ni (IPr*)(PPh3)Br2 (1) and Ni (IPr*)(PCy3)Br2 (2) (IPr* = 1,3‐bis(2,6‐bis (diphenylmethyl)‐4‐methylphenyl)imidazol‐2‐ylidene), were easily prepared in 78% and 89% yield, respectively. Both were characterized by elemental analysis and NMR spectroscopy, and 1 was subjected to X‐ray crystallography. Compared with 2 and its analogue bearing a less sterically demanding IPr ligand (IPr = 1,3‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene), complex 1 exhibited superior catalytic activity in the magnesium‐mediated reductive coupling of benzyl chlorides with aryl chlorides, featuring outstanding tolerance of both coupling partners with steric demand. This study discloses a ligand‐facilitated reductive coupling of benzyl chlorides with aryl chlorides, which provides a new and practical synthetic tool for the synthesis of diarylmethanes.

Heteroleptic Ni(II) Complexes Bearing a Bulky Yet Flexible IBiox-6 Ligand: Improved Selectivity in Cross-Electrophile Coupling of Benzyl Chlorides with Aryl Chlorides/Fluorides

“…On the basis of our studies on the design and catalytic applications of well-defined heteroleptic Ni­(II) complexes of NHCs, we herein report the preparation and molecular structure of the first heteroleptic Ni­(II) complexes containing an IBiox-type ligand ( 1 and 2 ). The preliminary investigation of their catalytic performances for the cross-electrophile coupling of benzyl chlorides with aryl chlorides or less reactive aryl fluorides in the presence of Mg turnings are also described.…”