Heteroatom Donor‐Decorated Polymer‐Immobilized Ionic Liquid Stabilized Palladium Nanoparticles: Efficient Catalysts for Room‐Temperature Suzuki‐Miyaura Cross‐Coupling in Aqueous Media

Abstract

Palladium nanoparticles stabilized by heteroatom donor-modified polystyrene-based polymer immobilized ionic liquids (PdNP@HAD-PIILP; HAD-PPh 2 , OMe, NH 2 , CN, pyrrolidone) are highly efficient catalysts for the Suzuki-Miyaura cross-coupling in aqueous media under mild conditions. Catalyst modified with phosphine was consistently the most efficient as it gave high yields across a range of substrates under mild conditions at low catalyst loadings. Incorporation of polyethylene glycol into the phosphine modified immobilised ionic liquid support improved catalyst efficacy by improving dispersibility and facilitating access to the active site. Moreover, each of the heteroatom modified catalysts was more active than the corresponding unsubstituted imidazolium-based polystyrene benchmark as well as commercial samples of Pd/ C. Catalyst generated in situ from either [PdCl 4 ]@PPh 2 -PIILP or its PEGylated counterpart [PdCl 4 ]@PPh 2 -PEGPIILP, by reduction with phenylboronic acid, outperformed their pre-formed counterparts for the vast majority of substrates examined. The turnover frequency of 16,300 h À1 obtained at room temperature is one of the highest to be reported for palladium nanoparticle-catalysed Suzuki-Miyaura cross-coupling between 4bromoacetophenone and phenylboronic acid in aqueous media under such mild conditions.

Pillarquinone‐Based Porous Polymer for a Highly‐Efficient Heterogeneous Organometallic Catalysis

“…We also compared the TOF value of Pd-PPQ with other existing heterogeneous catalysts reported in literatures. [35][36][37][38][39][40][41][42][43][44][45] Entry 1 ( Table 2) was used as an example and the comparison was summarized in Figure 4a. We concluded that Pd-PPQ reached unprecedented catalytic efficiency compared to literature reports!…”

Catalyst shuttling enabled by a thermoresponsive polymeric ligand: facilitating efficient cross-couplings with continuously recyclable ppm levels of palladium

“…55 However, heterocycles are likely to coordinate with transition metals, thus representing a challenging class of starting materials for metal-catalyzed reactions with low catalyst dosages. 56 With this method, a variety of heterocyclic compounds including pyridine (24)(25)(26)(27)(28), quinoline (29), carbazole (27), dibenzofuran (28), indole (30), pyrimidine (31-32), pyrazine (33), pyrazole (34), imidazo[1,2-a]pyrazine (35), thiophene (36)(37)(38)(39)(40), benzothiophene (41), and furan (42), could be used to generate corresponding products, representing the broadest substrate scope obtained with a polymeric catalyst as far as is known.…”

“…12,22,23 Based on previous achievements of using electron-rich phosphine ligands to promote SM couplings, [24][25][26][27][28][29][30][31] Carrow and co-workers revealed that a tri(adamantyl)phosphine-Pd complex catalyzed a process with low Pd loadings in an organic solvent. 13 Whereas polymeric materials loaded with Pd are easily recyclable for homo/heterogeneous SM couplings, [32][33][34][35][36][37][38][39][40][41][42] in comparison to small molecule catalysts, polymeric catalysts generally exhibit: (a) limited functional group tolerance, (b) decreased reactivity toward deactivated aryl chlorides, and (c) unsatisfactory compatibility with heterocycles. 43 Furthermore, tandem/ iterative catalysis based on chemoselective SM coupling [44][45][46] has rarely been realized with polymeric catalysts.…”

Biological and catalytic potential of sustainable low and high valent metal-Schiff base sulfonate salicylidene pincer complexes

“…At the optimal reaction condition, i.e. 6 hours heating at 100 C, the % yield of the cross-coupling product was monitored by GC-MS which displayed in percentages amount of the C-C product under the same sustainable conditions (50,49,61 and 39%, respectively), as shown in Table 9. Potassium carbonate is the most favored base for the C-C catalytic process, due to the strong interaction between the catalyst, solvent (H 2 O) and the base to enhance the catalytic potential.…”

“…46 Sustainably, the incorporated sodium sulfonate group to the synthesized Schiff base ligand improves its reactivity and the corresponding metal complexes under green conditions. 41 Ionic liquids, as imidazolium-and pyridinium-based liquids are of interest as solvents [47][48][49][50] or co-catalysts 51-54 for many C-C biaryls syntheses, e.g. Suzuki-Miyaura cross-coupling protocols.…”