2‐Hydroxyethyl‐Substituted Pd‐PEPPSI Complexes: Synthesis, Characterization and the Catalytic Activity in the Suzuki‐Miyaura Reaction for Aryl Chlorides in Aqueous Media

Abstract

In recent years, PEPPSI (Pyridine‐Enhanced Precatalyst Preparation Stabilization and Initiation) complexes have attracted attention in organometallic chemistry. This study contains the synthesis of the 2‐hydroxyethyl‐substituted Pd‐PEPPSI complexes and their catalytic activity in the Suzuki‐Miyaura reaction aryl chlorides in aqueous media. The Pd‐PEPPSI complexes have been prepared from the 2‐ hydroxyethyl‐substituted N‐heterocyclic carbene (NHC) precursors, palladium chloride and 3‐chloropyridine. The Pd‐PEPPSI complexes have been characterized by using 1H NMR, 13C NMR, FTIR spectroscopy and elemental analysis techniques. The Pd‐PEPPSI complexes have been examined as catalysts in the Suzuki‐Miyaura reactions in aqueous media with arylboronic acid derivatives. Also, they have demonstrated excellent activity in these reactions. Molecular and crystal structure of one of the 2‐hydroxyethyl substituted Pd‐PEPPSI complex was determined by single crystal X‐ray diffraction method. X‐ray studies show that the molecular structure adopts a slightly distorted square‐planar geometry with the palladium (II) center.

2‐hydroxyethyl‐substituted (NHC)PdI2(pyridine) (Pd‐PEPPSI) Complexes: Synthesis, Characterization and the Catalytic Activity in the Sonogashira Cross‐coupling Reaction

“…The FT‐IR data clearly indicated the presence of ν (OH) at 3431, 3475, 3458, 3347, 3408, 3438, 3397, 3469, 3465 and 3230 cm −1 for the (NHC)PdI 2 (pyridine) complexes ( 1 a‐j ), respectively. These NMR and FT‐IR data are consistent with literature ,. The results of the elemental analysis were evaluated and it was observed that the calculated values were very close to the found values.…”

“…(C−Br). However, the electron‐donor group on the benzene ring strengthens the bond by reducing the polarity of the covalent bond between the bromide atom and the carbon atom in the para position (C−Br) …”

“…The (NHC)PdX 2 L (L, pyridine derivative) complexes from metal‐NHC complexes are known as Pd‐PEPPSI (PEPPSI, Pyridine‐Enhanced, Precatalyst, Preparation, Stabilisation and Initiation) ,. The high catalytic activity of the Pd‐PEPPSI complexes is principally attributed to the rapid elimination of the pyridine derivative co‐ligand in the catalytic cycle and to the high stability of the Pd‐NHC bond .…”

“…[15][16][17][18][19][20][21] The (NHC)PdX 2 L (L, pyridine derivative) complexes from metal-NHC complexes are known as Pd-PEPPSI (PEPPSI, Pyridine-Enhanced, Precatalyst, Preparation, Stabilisation and Initiation). [22,23] The high catalytic activity of the Pd-PEPPSI complexes is principally attributed to the rapid elimination of the pyridine derivative co-ligand in the catalytic cycle and to the high stability of the Pd-NHC bond. [24][25][26][27][28] In recent years, the Pd-PEPPSI complexes, the catalytic properties of which have been discovered by Organ et al, were synthesized.…”

Efficient Suzuki–Miyaura C-C Cross-Couplings Induced by Novel Heterodinuclear Pd-bpydc-Ln Scaffolds

“…This synthesis approach has revolutionized the production of advanced materials [15,16,17,18], pharmaceuticals [19,20,21], agrochemicals [21,22], liquid crystals [23], and natural or biologically active compounds [24,25,26,27,28], etc. Numerous attractive strategies have been developed to address the ample scope of this catalytic process including the utilization of palladium nanoparticles [29,30,31,32,33,34,35], or palladium immobilized on magnetic nanoparticles [36] and natural supports [37], use of nucleophilic carbene ligands (mostly NHCs) [38,39,40,41,42,43,44,45,46], Schiff bases [47,48], water-soluble ligands like poly(ethylene glycol)-functionalized N-heterocyclic carbenes [49], thiourea [50] or phosphines [51,52], induction by microwave (MW) acceleration [53,54], use of “greener” solvents, such as water [55,56,57,58,59,60,61,62,63,64,65] (activated by MW [66,67] or in catalysis under micellar conditions [68] for enhancing the solubility of the aromatic halide), water–DMF […”