Palladium(II) Complexes of (2,6‐Dibenzhydryl‐4‐methylphenyl)diphenyl‐phosphane: Synthesis, Structural Studies, and Catalytic Arylation of Imidazoles Under Aerobic Conditions

Abstract

AbstractThe synthesis and structural studies of palladium(II) complexes of sterically demanding mono‐phosphine Ar*PPh2 (1) (Ar*=2,6‐dibenzhydryl‐4‐methylphenyl) are described. The reactions of 1 with [Pd(COD)Cl2] and [Pd(η3‐C3H5)Cl]2 in 2 : 1 molar ratios afforded mononuclear complexes trans‐[PdCl2{(PPh2Ar*)‐κ1‐P}2] (2) and [Pd(η3‐C3H5)Cl{(PPh2Ar*)‐κ1‐P}] (3), respectively. Both the complexes have been fully characterized through NMR spectroscopy, elemental analyses, and single‐crystal X‐ray analysis. The molecular structures of 2 and 3 showed C−H⋅⋅⋅π interactions between methine hydrogen of one of the Ph2CH groups with the centroid of one of the phenyl rings of the PPh2 group. Complex 2 also showed intramolecular π⋅⋅⋅π stacking interactions between the phenyl rings of Ph2CH and PPh2 groups. In addition, complex 2 also showed C−H⋅⋅⋅Pd anagostic interaction between the methine hydrogen of one of the Ph2CH groups and the palladium center. The palladium complex 2 is found to be an efficient catalyst for the direct C‐5 arylation of imidazole derivatives under aerobic conditions.