New Pd-PEPPSI complexes bearing meta-cyanobenzyl-Substituted NHC: Synthesis, characterization, crystal structure and catalytic activity in direct C-H arylation of (Hetero)arenes with aryl bromides

The prestige of the PEPPSI (Pyridine-Enhanced Precatalyst Preparation Stabilization and Initiation) complexes in organometallic chemistry is increasing day by day. Herein, the well-defined seven meta-cyanobenzyl-substituted N-heterocyclic carbene (NHC)-Pd(II)-pyridine (Pd-PEPPSI) complexes were synthesized using palladium acetate, which unlike general procedure is a more economical method than palladium chloride. The new Pd-PEPPSI complexes were obtained from the reaction of the cyanobenzyl substituted NHC precursors and palladium acetate in pyridine. The new complexes have been fully characterized by H-1 NMR, C-13 NMR, FTIR spectroscopy and elemental analysis techniques. Also, the X-ray diffraction method was used to determine the single-crystal structure of a complex. The Pd-PEPPSI complexes have been examined as catalysts in the direct arylation reactions of 2-n-butylfuran and 2-n-butylthiophene with aryl bromide. All complexes have demonstrated excellent activity in these reactions. The Molecular and crystal structure of one of the cyanobenzyl substituted Pd-PEPPSI complexes was determined by the single-crystal X-ray diffraction method. X-ray diffraction studies show that the molecular structure adopts a slightly distorted square-planar geometry with the palladium (II) center. (c) 2019 Elsevier B.V. All rights reserved.