Mixed Phosphite/N-Heterocyclic Carbene Complexes: Synthesis, Characterization and Catalytic Studies

Abstract

A series of mixed P(OR) 3 /NHC Pd complexes was synthesized and fully characterized. The steric properties of both types of ligands were computationally determined using X-ray data. These structural studies clearly show that N-heterocyclic carbenes modulate their bulkiness with respect to the steric requirements of the coligands. Catalytic studies were performed using this new class of complexes for the Suzuki-Miyaura reaction. It was found that alkoxide or hydroxide bases and/or alcohols were necessary to achieve good catalytic activity. Mechanistic studies were undertaken in order to gain insights into the role of alkoxide groups. These studies suggest that alcohols or alkoxide groups play a major role in the activation of the precatalyst to generate the catalytically active species. Catalytic studies proved these systems to be efficient using 0.1 mol % of Pd loading for the coupling of aryl, benzyl, and heterocyclic chlorides with boronic acids.

Di- and tri-nuclear-palladium complexes bearing piperidoimidazolin-2-ylidenes: synthesis, characterization, and catalytic applications

“…The PdeC carbene bonds [1.961(8) A for 1, 1.941 (14), 1.964(12) A for 2c] and PdeN bonds [2.108(6) A for 1, 2.157(9), 2.149(10) A for 2c] are comparable to those found in mononuclear pyridine/NHC palladium complexes, PdCl 2 (NHC)(L) [e.g., PdeC carbene : 1.990(3) for PdCl 2 (SIPr)(L), (SIPr¼N,N 0 -bis(2,6-diisopropylphenylimidazolidin-2-ylidene, L¼3-chloro-pyridine); 22 PdeC carbene : 1.953(4) for PdBr 2 ( i Pr-Bimy)(L), ( i Pr-Bimy¼N,N 0 -diisopropylbenzimidazolidin-2-ylidene, L¼pyridine) 23 ].…”

Polymer precursors from catalytic reactions of natural oils

“…Moreover, this base was found to be the most efficient one in a previous study on NHCphosphite Pd(II) pre-catalysts for the Suzuki-Miyaura coupling reaction. 260 Therefore, sodium hydroxide was selected for this study.…”

[{Pd(μ‐OH)Cl(IPr)}2]—A Highly Efficient Precatalyst for Suzuki–Miyaura Coupling also Able To Act under Base‐Free Conditions

“…Among these processes, Suzuki–Miyaura (SM) cross‐coupling is one of the most frequently used in organic synthesis . Presently, a number of NHC palladium complexes, including a family of [PdCl 2 (NHC)(pyridine)] (PEPPSI) precatalysts, analogues bearing various throw‐away ligands, and related dimeric complexes of the type [{Pd(μ‐Cl)(Cl)(NHC)} 2 ], have been reported to be excellent precatalyst for Suzuki–Miyaura coupling ,…”