N-heterocyclic carbene ligands with a bicyclic framework fused with either naphthalene or anthracene

N-heterocyclic carbene (NHC) ligands equipped with a bicyclic framework fused with either naphtha-lene or anthracene (NCPSI and ACPSI, respectively) were synthesized, and their silver and iridium com-plexes were obtained. Tolman's electronic parameter (TEP) values for these NHC ligands were calculated by using the Ir complexes, which indicated that the electron-donating ability of these NHCs was almost identical to that of the structurally related NHCs, DHASI and BCPSI, that we had previously reported. The structures of [(NHC)AgCl] and [Ir(COD)Cl(NHC)] were analyzed via XRD study, which showed struc-tural changes that depended on the bound metals. Although the NHCs analyzed in this study involve the same bicyclo[2.2.1]heptene core, three aromatic rings, benzene, naphthalene, and anthracene, caused different interplanar angles between the aromatic rings and the NHC's five-membered rings. The regio-selectivities during copper-catalyzed allylic arylation were found to be related to the interplanar angles of the [(NHC)AgCl] complexes, indicating that the interplanar angles would be a useful factor in tuning the steric properties of these NHC ligands.(c) 2022 Elsevier B.V. All rights reserved.

Automated summary

N-heterocyclic carbene (NHC) ligands with bicyclic frameworks fused with naphthalene or anthracene were synthesized and their silver and iridium complexes were obtained. The electron-donating ability of these NHCs was found to be similar to structurally related NHCs that were previously reported. The structures of [(NHC)AgCl] and [Ir(COD)Cl(NHC)] were analyzed, revealing structural changes depending on the bound metals. The interplanar angles between the aromatic rings and the NHC's five-membered rings were found to be a useful factor in tuning the steric properties of these NHC ligands.