Heterogeneous Pd/POSS Nanocatalysts for C–C Cross‐Coupling Reactions

Abstract

An insoluble solid support of N−heterocyclic imidazolium‐functionalized cage‐like silsesquioxane (SQ); Bim‐SQ, was synthesized by nucleophilic substitution of octakis(3‐chloropropyl)octasilsesquioxane with an excess bis‐(imidazol‐1‐yl)methane and investigated as a new organic‐inorganic hybrid support. In the presence of Bim‐SQ, Pd(II) from [PdCl4]2− can be stabilized via both electrostatic interactions and imidazole‐N‐coordination, giving an amorphous material of Pd(II)@Bim‐SQ. Subsequent in situ reduction of Pd(II)@Bim‐SQ during Suzuki−Miyaura cross‐coupling reactions afforded monodispersed Pd nanoparticles (2.33 ± 1.50 nm) stablized on Bim‐SQ support, PdNp@Bim‐SQ with Pd loading up to 14% w/w. Catalytic studies revealed that the pre‐catalyst Pd(II)@Bim‐SQ was active heterogeneous catalyst for Suzuki−Miyaura cross‐coupling reactions, having the maximum TOFs of 5400 h−1 under mild conditions and in aqueous ethanol medium. Furthermore, PdNp@Bim‐SQ was also shown to be an efficient catalyst for Heck reactions. Simple catalyst recovery and reusability of PdNp@Bim‐SQ for at least 5 catalytic cycles without loss of activity were also demonstrated.

Silsesquioxane‐Containing Hybrid Nanomaterials: Fascinating Platforms for Advanced Applications

“…Imidazolium‐containing POSS was synthesized and used to stabilize Pd nanoparticles via both electrostatic interactions and imidazloe‐N‐coordination. The obtained Pd@POSS nanoparticles worked as an active heterogeneous catalyst for Suzuki–Miyaura cross‐coupling reactions and Heck reactions with good reusability …”

“…The obtained Pd@POSS nanoparticles worked as an active heterogeneous catalyst for Suzuki-Miyaura cross-coupling reactions and Heck reactions with good reusability. [98] Through a green synthetic methodology without the addition of an alkali solution, Mohapatra's group fabricated octakis(3-(1-methylimidazolium) propyl) octasilsesquioxane (POSS-MPIm)-supported palladium NPs. As shown in Figure 3, POSS-MPImCl reacted with Pd(OAc) 2 for 72 h at 100 °C via a solid state annealing process to form Pd(II)-MPIm-POSS (1).…”

Octa[4‐(9‐carbazolyl)phenyl]silsesquioxane‐Based Porous Material for Dyes Adsorption and Sensing of Nitroaromatic Compounds

“…In the preparation of silsesquioxane-based porous polymers,w hether cubic cages keep intact or not depends on many factors, for example, monomer types, reactiont ype or condition etc. Usually, cage tends to collapsei no rder to release structurals tress in the stiff network formed by Heck, Sonogashira,S uzuki and Ullmann reactiona nd hierarchicalp orous structures easily formed; [9,19] however,t he flexible linking units helpt ok eep cage intact and bimodal pore structures usually formed, for ex-ample,s ome silsesquioxane-based porous polymers, which are prepared by the Friedel-Crafts reaction of octavinylsilsesquioxane with aromatic compounds to form the flexible linker of CH 2 -CH 2 -Ar. [7a] The destruction of cage in this case might be due to the following factors.…”

Triazole‐based ligands functionalized silica: Effects of ligand denticity and donors on catalytic oxidation activity of Pd nanoparticles

“…[10] On the contrary, the heterogeneous Pd NPs catalysts require only molecular oxygen as oxidant and are reusable with usually low metal contamination in the oxidized products. [11][12][13] Although chemically robust, N-rich aromatic triazole compounds have been demonstrated as good stabilizers for MNPs, [14] only a handful of examples involving Pd NPs catalysts supported by triazole-functionalized solid supports have so far been reported. [11][12][13] Although chemically robust, N-rich aromatic triazole compounds have been demonstrated as good stabilizers for MNPs, [14] only a handful of examples involving Pd NPs catalysts supported by triazole-functionalized solid supports have so far been reported.…”

“…Recently, we have shown that Pd NPs stabilized by functionalized polyhedral oligomeric silsesquioxanes (POSS) serve as active catalysts for aerobic alcohol oxidation and Suzuki-Miyaura cross coupling reactions. [11][12][13] Although chemically robust, N-rich aromatic triazole compounds have been demonstrated as good stabilizers for MNPs, [14] only a handful of examples involving Pd NPs catalysts supported by triazole-functionalized solid supports have so far been reported. [15][16][17][18][19] Notably, Astruc and co-workers showed that Pd NPs stabilized on tris (triazolyl)-functionalized silica-coated magnetic supports could quantitatively convert benzyl alcohol to benzaldehyde in toluene at 90°C in air.…”