N-Acylamidine Palladium(II) Complexes. Synthesis, Structures, and Catalytic Activity for Suzuki−Miyaura Cross-Coupling Reactions:  Experiments and DFT Calculations

Abstract

N-Acylamidines 2 are easily prepared by acylation of amidines 1. Upon treatment with PdCl(2)(PhCN)(2), they form 2:1 PdCl(2) complexes 3 with trans configuration, acting as monodentate ligands via the nitrogen atom remote from the carbonyl group. The structures of the complexes 3a-c in the solid state were obtained by X-ray crystallography. As studied by DFT calculations on 2:1 model complexes, many isomeric structures 6 with different conformations and configurations are associated with local minima on the energy hyperface within an energy range of 4 kcal/mol. The complexes 3 show very high catalytic activity in Suzuki-Miyaura cross-coupling reactions, either as isolated crystals or prepared in situ without isolation.

Nanocrystalline Titania‐Supported Palladium(0) Nanoparticles for Suzuki–Miyaura Cross‐Coupling of Aryl and Heteroaryl Halides

“…[7,8] The use of such ligands is undesirable because of their toxicity and airas well as moisture-sensitive nature with conversion to, for example, phosphine oxide species. However, few phosphine-free N-based ligands, such as NheteroA C H T U N G T R E N N U N G cyclic carbenes, [9] N,O-or N,N-bidentate ligands, [10] aryloximes, [11] arylimines, [12] N-acylamidines, [13] and simple amines, [14] have been used in the Suzuki cross-coupling reaction. Despite the synthetic elegance and high turnover numbers, the non-reusability of the precious palladium precludes wide synthetic applications in the pharmaceutical industry.…”

A Tetranuclear Hydroxo‐Bridged Copper(II) Complex with PrimaryN‐Acylamidines as Ligands: Preparation, Structural, and Magnetic Characterisation

“…[13] In another publication we presented experimental and theoretical results concerning the complexation of substituted N-acylamidine ligands 1 towards palladium(ii), the structures of the complexes as well as their catalytic properties in cross-coupling reactions. [15] Results and Discussion Synthesis N-Acylamidines (1) are interesting yet rarely used ligands for metal complexation. They resemble β-dialkylamino-acroleine derivatives which have found various applications in coordination chemistry.…”

Pyridine‐Based Oligonitriles as Pincer Ligands for Palladium(II), Copper(II), Cobalt(II), and Nickel(II) Ions

“…[5] Triazapentadienes may also be considered to be short examples of oligonitriles. These compounds also form six-membered chelate complexes, for example with Co II , Ni II , Cu II , Pd II and Zn II ions.…”