Mixed phosphine/N-heterocyclic carbene palladium complexes: synthesis, characterization and catalytic use in aqueous Suzuki–Miyaura reactions

Abstract

A series of N-heterocyclic carbene (NHC)/PR3 palladium(II) and palladium(0) complexes has been synthesized and fully characterized. X-ray crystallographic data have allowed comparison of ligand steric properties. The NHC ligand was found to vary its steric properties as a function of the phosphine co-ligand. These complexes display interesting catalytic properties in the Suzuki-Miyaura reaction performed in aqueous media. The pre-catalyst [PdCl2(IPr)(XPhos)] (IPr = N,N'-bis-(2,6-diisopropylphenyl)imidazol-2-ylidene; XPhos = 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl) was found to be the most efficient system, promoting the coupling of a wide range of aryl chlorides with boronic acids in aqueous media with a typical catalyst loading of 0.03 mol%.

Utilizing a zwitterionic approach for the synthesis of late transition metal – triphosphenium ion coordination compounds

“…In the core of 1Pd, the palladium atoms are square planar with the two phosphorus ligands (1) and also the two phenyl groups being in a cis arrangement to one another. The P-P bond lengths are all similar and in the range that would be expected 44 For the bisortho-metallated platinum compound (1Pt), a partial crystal structure analysis confirms that the gross connectivity is as described and is consistent with the NMR spectral data. The structure was best solved and refined as a C-monoclinic structure, with a thermal ellipsoid diagram and the crystallographic parameters listed in the supporting information.…”

Synthesis of N‐Heterocyclic Carbene–PdII–2‐Methyl‐4,5‐dihydrooxazole Complexes and Their Application Toward Highly Chemoselective Mono‐Suzuki–Miyaura Coupling of Dichlorobenzenes

“…Compound 7 u : Colorless liquid; 1 H NMR (CDCl 3 , 500 MHz): δ =7.63–7.61 (m, 2 H), 7.58–7.56 (m, 2 H), 7.49–7.42 (m, 3 H) 7.35–7.25 (m, 6 H), 2.32 ppm (s, 3 H); 13 C NMR (CDCl 3 , 125 MHz): δ =142.4, 141.8, 141.1, 141.0, 135.4, 130.3, 129.8, 128.8, 128.5, 128.1, 128.0, 127.34, 127.31, 127.2, 125.8, 125.5, 20.5 ppm.…”

Synthesis of Imidazolium Precursors for the Hydroxyl-Group-Modified N-Heterocyclic Carbenes and Applications of the in situ Generated Carbene Ligands in Suzuki-Miyaura and Sonogashira Coupling Reactions

“…Selected examples of reported NHC ligands with hydroxyl-functionalized side arms or related metal complexes 图 2 咪唑盐 3a～3d 和 4a, 4b 结构图 Figure 2 Structure of the imidazolium salts 3a～3d and 4a, 4b N-杂环卡宾钯配合物作为一种高效的催化剂, 已经 被成功应用于许多催化反应中 [9] . 其中, Suzuki-Miyaura 偶联反应是合成联芳类化合物最有效的合成方法 [10] , 并且, 近年来绿色化学的观念逐渐深入人心 [11,12] . 因此, 我们试图在低污染和低能耗下实现对 Suzuki-Miyaura 偶 联反应的高效催化.…”