SBA‐15/POSS‐Imidazolium Hybrid as Catalytic Nanoreactor: the role of the Support in the Stabilization of Palladium Species for C−C Cross Coupling Reactions.

Abstract

Supported imidazolium modified polyhedral oligomeric silsesquioxanes (POSS) on SBA‐15 have been used as platform for Pd(II) species. The so‐obtained material was firstly characterized by means of TGA, solid state NMR, TEM, XPS, SAXS, porosimetry and ICP‐OES and it was successfully tested as pre‐catalyst in C−C cross couplings, namely Suzuki‐Miyaura and Heck reactions. In both cases, the solid proved to be highly efficient and easily recoverable from the reaction mixture. The recyclability was verified for up to seven cycles without showing any activity decrease. Interestingly, only Pd(II) was detected in the reused catalyst in the Heck reaction. Therefore, the versatility of the material was investigated by using various aryl halides. Our palladium nanocomposite was able to promote both Suzuki and Heck reactions down to 0.0007 mol% showing outstanding turnover frequency (TOF) values of 114,286 and 32,381 h−1, respectively. Comparison with the palladium catalyst on SiO2‐POSS‐imidazolium support showed interesting differences in terms of stabilization of Pd species and recyclability. The excellent outcome of the reactions could be ascribed to the textural properties of the SBA‐15 support and the presence of the imidazolium‐POSS nanocage within the pores of SBA‐15, that worked as a sort of nanoreactor.magnified image

Amino‐Induced 2D Cu‐Based Metal–Organic Framework as an Efficient Heterogeneous Catalyst for Aerobic Oxidation of Olefins

“…After six successive cycles, the Cu-AIA-PC-Pd catalystr emains substantially active and no significant decreasesi nt he catalytic efficiency are observed ( Figure S22). Compared with the catalysts reported in literatures (TableS5), [73][74][75][76][77][78][79][80][81][82][83] the obtained Cu-AIA-PC-Pd also exhibits excellentc atalytic activity.T he results confirm that Cu-AIA as a2 Dcarriertos upport metal catalysts is feasible.…”

Tailor-Made POLITAG-Pd0 Catalyst for the Low-Loading Mizoroki–Heck Reaction in γ-Valerolactone as a Safe Reaction Medium

“…Metal nanoparticles have become widely interesting for the development of highly effective catalytic systems, exploiting larger surface properties. , However, due to their obvious small size, heterogeneous matrix supports (i.e., silica, − zirconia, , polymers, − and carbon-based supports) − are often required to optimize their use. The major challenge to exploit the high efficiency of palladium nanoparticles is the control of size distribution, which is strictly connected to the catalyst activity.…”

“…One of the strategies utilized to avoid aggregation/agglomeration of palladium particles is the deployment of ionic moieties. − The presence of organic cation with an inorganic counterion is effective to coordinate and stabilize the particles of metals. Furthermore, these ionic tags, by complexing the metal, can also prevent and minimize palladium leaching in solution, making the procedure cleaner and also the overall catalytic system reusable. ,,− …”

An Imidazole‐Rich Pd(II)‐Polymer Pre‐catalyst for the Suzuki‐Miyaura Coupling: Stability Influenced by Dissolved Oxygen and Reactants Concentration

“…In addition, efforts to develop easily recoverable imidazolebased catalysts have been reported, such as immobilization of Pd in nano silicon functionalized with a N-heterocyclic carbenes, [14] covalent organic frameworks, [24] silsesquioxane matrix, [39] and a SBA-15 derivative. [40] Although the materials display high catalytic activity in cross-coupling reactions, their preparation involve many steps, rendering them less practical for industrial applications. [41] This issue brought to attention by De Vries and co-workers [11,42,43] who pointed out the disadvantages in the immobilization of Pd on heterogeneous supports prepared by dispendious synthetic routes, with long reactions time and under harsh conditions.…”