Development of Pd Supported Catalysts Using Thiol‐Functionalized Mesoporous Silica Frameworks: Application to the Chemo‐ and Regioselective C‐3 Arylation of Free‐Indole. Issue 9 (17th February 2021)

• Record Type: Journal Article
• Authors: Renom Carrasco, Marc; Khodja, Walid; Demarcy, Clément; Veyre, Laurent; Camp, Clément; Thieuleux, Chloé
• Is Part Of: European journal of inorganic chemistry. Issue 9(2021)
• Page Start: 814
• Page End: 820
• Publication Date: 2021-02-17
• Subjects: Arylation -- C−H activation -- Heterogeneous catalysis -- Mesoporous functionalized silica -- Palladium; Chemistry, Inorganic -- Periodicals; Organometallic chemistry -- Periodicals; Bioinorganic chemistry -- Periodicals; Solid state chemistry -- Periodicals; 546
• DOI: 10.1002/ejic.202001086
• Languages: English
• ISSNs: 1434-1948

Abstract

Abstract: We report here the development of Pd‐supported catalysts for the selective C ‐3 arylation of free‐indole using thiol‐functionalized silica supports to anchor the palladium centers. The palladium (II) complex, Pd(OAc)2, was efficiently loaded into various thiol‐functionalized mesostructured silicas at room temperature. These materials exhibit different contents of surface SH groups (0.3 to 1.8 SH/nm 2 ) and various SH/Pd molar ratios from 6 to 65. It was found that the catalysts containing the most isolated surface SH groups (0.3 SH/nm 2 ) and the highest loading of Pd were the most active, reaching 70 % of conversion, 1400 as turnover numbers and 100 % selectivity in the C ‐3 arylated product using only 0.05 mol % of Pd. However, a leaching of active Pd species (1.7 ppm) was detected. The best compromise was found for a specific solid containing isolated surface thiol groups (0.3 SH/nm 2 ) and a very low loading of Pd (SH/Pd=65). It exhibited a high TON (608) with a very low Pd leaching of 0.5 ppm in the course of the catalytic reaction. These results thus illustrate that both surface SH sites isolation and concentration, as well as the SH/Pd molar ratio are key parameters to access high catalytic performances and very low leaching of metal during catalysis. Abstract : A highly active, leaching resistant and re‐usable Pd‐based supported catalyst for the C ‐3 selective arylation of free‐indole was prepared. It was obtained by coordination of Pd(OAc)2 into a mesostructured silica matrix containing surface thiol groups. It was shown that the regular distribution and the isolation of thiol groups along with the amount of loaded Pd per SH group play a key role to develop this promising catalytic material.