New bis(N‐heterocyclic carbene) palladium complex immobilized on magnetic nanoparticles: as a magnetic reusable catalyst in Suzuki‐Miyaura cross coupling reaction

Abstract

A new bis(N-heterocyclic carbene) (NHC) palladium complex supported on silica coated magnetic nanoparticles (MNPs) was prepared using the reaction of synthesized Pd-NHC complex with MNPs. The Pd-NHC complex was prepared using the reaction of a hydroxyl-functionalized bis-imidazolium ionic liquid. The Pd-NHC organometallic complex was used as a heterogeneous recyclable and active catalyst in the Suzuki-Miyaura reaction and various aryl halides were coupled with arylboronic acids in order to synthesize diverse biaryls in good to excellent yields. The prepared catalyst was characterized by use of some different microscopic and spectroscopic techniques including elemental analysis, FT-IR spectroscopy, diffuse reflectance UV-Vis spectrophotometery, scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM) and X-ray diffraction (XRD). The Pd-NHC catalyst system is a magnetic reusable catalyst and it can be separated from the reaction mixture using an external magnetic field. The catalyst was reusable in the Suzuki-Miyaura coupling reaction at least for 6 times without significant decreasing in its catalytic activity.

Zwitterionic Rhodium and Iridium Complexes Based on a Carboxylate Bridge-Functionalized Bis-N-heterocyclic Carbene Ligand: Synthesis, Structure, Dynamic Behavior, and Reactivity

“…Chemical shifts are reported in ppm relative to tetramethylsilane and coupling constants (J) are given in Hertz (Hz). The 1 H and 13 C{ 1 H} spectra were referenced using the residual solvent signal as internal standard, while 19 F and 31 Electrospray Ionization (ESI) mass spectra were recorded using a Bruker Esquire3000 plus™ ion-trap mass spectrometer equipped with a standard ESI source. Samples were introduced on a continuous flow of 0.2 mL/min.…”

“…[26][27][28][29][30] In fact, advantage of the presence of an hydroxyl group has been taken for the immobilization of palladium complexes on solid supports. 27,31 As far as we know, the only example of tripodal  3 C,C,O coordination is a rhodium(III) compound having a bis-NHC ligand functionalized with a 2-phenolate substituent in the bridge. 16 Inspired by this ligand scaffold and with the aim of developing our research on the synthesis and catalytic applications of transition-metal complexes containing functionalized NHC ligands with a hemilabile character, 32, 33,34, we envisaged the potential of a carboxylate-functionalized methylene-bridged bis-NHC ligand for the construction of a versatile metal-ligand platform.…”

About Solid Phase vs. Liquid Phase in Suzuki-Miyaura Reaction

“…The reaction of 4-iodoanisole with phenylboronic acid catalysed by a Pd-NHC complex supported on silica coated magnetic nanoparticles (Pd-NHC-MNP) was performed for 6 successive runs at 80 • C (Entry 31, Table 3). The yield decreased continuously from 97% to 88% in the last run, which gives a TON (TOF tot ) equal to 4633 (908 h −1 ) [88]. Considering the ICP-AES analysis showing 0.15% of Pd leaching, corresponds values for TON (TOF leach ) are 539,000 (634,000 h −1 ).…”

“…Transmission electron microscopy (TEM) is an illustrative method used by many authors to compare images of the surface before and after the reaction and try to get an information about the absence of leaching or aggregation. Several authors have used this technique without finding any variation between the fresh and the used catalyst, for TONs between 300 and 1200 [8,52,65,69,88]. Other authors have been able to see a variation of the particle size for TONs between 1300 and 6000 [74,75,85].…”

Advances in Magnetic Nanoparticles-Supported Palladium Complexes for Coupling Reactions

“…Faregh-Alamdari and co-workers synthesized a catalyst for a Suzuki‒Miyaura cross-coupling reaction based on bis( N -heterocyclic carbene) palladium complex supported on silica-coated magnetic NPs (MNPs) by treatment of the magnetic NPs (D) with thionylchloride. In this approach, the Pd-NHC complex (C) was prepared from the reaction of a hydroxyl-functionalized bis-imidazolium ionic liquid (B) with Pd(OAc) 2 ( Scheme 75 ) [ 61 ].…”