Macrocycles of Axially Chiral and Racemic N-Heterocyclic Carbene Silver(I), Gold(I) and Palladium(II) Complexes: Synthesis, Characterization and Computational Structures

In this study, Ag(I), Au(I) and Pd(II) bis-N-hetero-cyclic carbene (NHC) complexes derived from axially chiral R-1,1′-binaphthyl-2,2′-diol (R-BINOL) and racemic biphenyl-2,2′-diol scaffolds have been synthe-sized. The metallation of these bis-imidazolium and bis-triazolium types of ligand precursors of R-BINOL and biphenol unit, viz. (1–4)d has been achieved using standard procedure. The {[L(L′-NHC)₂]Ag}Cl-type, chiral (1–2)e and racemic (3–4)e complexes have been obtained by the treatment of ligand with Ag₂O. Similarly, chiral Pd(II) (1f) and Au(I) (1g) complexes have been synthesized and analysed using spectroscopic techniques. The geometry-optimized structures obtained through the density functional theory display good proximity with the reported X-ray structures of similar type of Ag(I), AAu(I) and Pd(II) complexes.