Cyclometalated Iridium(III) Complexes Containing Benzoxazole Derivatives and Different Ancillary Ligands for Catalytic Oxidation of Toluene

Abstract

A series of cyclometalated iridium(III) complexes that have the general formula [(C^N)2Ir(NR)(X)] (C^N = monoanionic bidentate cyclometalating ligands; NR = pyridine derivatives; X = Cl− or I−) are designed, prepared, and applied for the transformation of toluene to benzaldehyde using a clean, highly efficient, and environmentally-friendly process. The activation energies that are needed for the catalytic oxidation of toluene when using these complexes as catalysts are quite low: between 22.9 and 30.8 kcal mol−1. The catalytic frequencies (TOF) are fairly high (up to 7.0 × 102 h−1) with excellent reliability, and the turnover number (TON) can reach 4.2 × 103 after 6 h of processing time. Catalytic tests, X-ray absorption near-edge structure (XANES), and kinetic modeling are used to derive detailed insights into the characteristics of the catalysts and their effects on the reactions that are featured in the catalytic oxidation of toluene.

Solvent-free liquid-phase selective catalytic oxidation of toluene to benzyl alcohol and benzaldehyde over CeO2–MnOx composite oxides

“…Instead, due to the reaction safety (temperature <200 °C) and high selectivity, the liquid-phase aerobic oxidation of toluene was industrially first adopted, which avoided the production of undesirable low value-added products by deep oxidation. [20][21][22] Peta et al explored Ticontaining mesoporous silica catalysts for the oxidation of toluene with H 2 O 2 , giving ∼100% selectivity to BAL and 98% toluene conversion. 23 Deng et al developed a metalloporphyrin/NHPI/CTAB composite catalytic system and obtained 40.9% toluene conversion with 28.5% selectivity to BAL and BOL.…”

Graphene oxide–iridium nanocatalyst for the transformation of benzylic alcohols into carbonyl compounds

“…We have previously demonstrated that iridium complexes are highly active catalysts for redox reactions, such as the reduction of carbon dioxide to carbon monoxide, 80 and the selective oxidation of toluene to benzaldehyde. 81,82 Here, graphene oxideiridium complex (GO-Ir complex) was used as a heterogeneous catalyst for a heterolytic catalysis by ultrasonication. The reaction condition is quite simple (Fig.…”

A reduced graphene oxide-supported iridium nanocatalyst for selective transformation of alcohols into carbonyl compounds via a green process

“…We have previously demonstrated that iridium complexes are highly active catalysts for some reactions, such as the selective oxidation of toluene to benzaldehyde and the reduction of carbon dioxide to carbon monoxide [55][56][57][58]. Here, we evaluated the catalytic activity of RGOIrNc compared with GO, RGO, GOIr and an iridium catalyst (IrNc) for the transformation of benzyl alcohol into benzaldehyde via ultrasonication.…”