Cationic versus Anionic Palladium Species in the Suzuki–Miyaura Cross‐Coupling

Abstract

The cationic complex [(pym‐Im‐Me)2PdCl][PF6] (pym = pyrimidyl; Im = imidazolin‐2‐ylidene) has been identified as a highly active and reliable catalyst in the Suzuki–Miyaura cross‐coupling reaction in ethanol for a wide range of substrates without the need for an excess of boronic acid. The catalytic activity of the cationic complex is retained at very low catalyst loadings, whereas quick decomposition occurs when using the anionic complex [Bu4N][Pd(DMSO)Cl3] (DMSO = dimethyl sulfoxide). Further investigations of the induction period, the effect of catalyst poisons, and SEM analysis of the particles formed under catalytic conditions show that in both cases the catalytically active species is – at least partially – heterogeneous.

Cyclometalated Palladium NHC Complexes Bearing PEG Chains for Suzuki–Miyaura Cross-Coupling in Water

“…The initial reaction conditions were inspired by our previous results obtained in organic solvents (Table ). ,, However, the pronounced differences between water and organic solvents made it necessary to reoptimize the reaction conditions. When we used potassium phosphate as a base in water without additives, we only obtained trace amounts of product 10a (Table , entry 1).…”

“…In addition, the yield of orthosubstituted biphenyls, such as 10g,i, was as high as for the other substrates, while typically lower yields would be expected. 123,134 Thus, we synthesized different biphenyls with more than one ortho substituent and still achieved excellent yields for compounds 10k−m. However, bis-ortho-substituted boronic acids were less reactive, producing compound 10m in just 48% yield.…”

Actinyl-Modified g-C3N4 as CO2 Activation Materials for Chemical Conversion and Environmental Remedy via an Artificial Photosynthetic Route

“…Motivated by the natural photosynthetic process, metal catalysts (mostly transition metals), ligated by reducing agents, have been used numerous times in synthetic chemistry with the desire to activate CO 2 , by lowering its thermodynamic and kinetic barriers. − However, the commercial applications of these catalysts are limited due to their low activities with regard to the specific selectivity of the CO 2 reduction reaction (CO 2 RR) and its competition with the hydrogen evolution reaction (HER) in aqueous media. ,− Efficient CO 2 activation catalysts thus require suitable electronic structures, which can facilitate electron transfer, along with the ability to optimally (neither too weak nor too strong) hold the reaction intermediates. , …”