Anaerobic oxidation of methane and its homologues in the presence of gold compounds

Catalysts for C–H functionalization: Platinum, gold and even nanodiamonds

“…In a biomimetic Au-rutin system, its value of 12 M 1 min 1 [ 93] is close to the upper limit constant value in a natural system. Therefore, the Aurutin-K 3 Fe(CN) 6 with rutin or quercetin as ligands are able to activate aliphatic -bonds of lower alkanes in mild conditions [96].…”

“…In the biomimetic systems, "noble" gold catalyzes the oxidation of light alkanes (C 1 -C 3 ) under aerobic or anaerobic conditions [80,82,93 ]. Bimolecular rate constant in the latter case is close to the upper limit of the constant in the natural system.…”

“…This conclusion allows one to interpret consistently the two-order increase in oxidation rate for light alkanes (methane, ethane, propane) in the biomimetic Au-rutin system at 25° in anaerobic conditions in the presence of one-electron oxidant K 3 [Fe(CN) 6 ] (Fig. 11) [93].…”

Direct Partial Oxidation of Methane Catalyzed by an In Situ Generated Active Au(III) Complex at Low Temperature in Ionic Liquids

“…The partial oxidation of CH 4 in homogeneous systems has attracted considerable interest since Shilov et al reported the direct conversion of CH 4 to CH 3 OH using Pt II as the C–H activation catalyst and Pt IV as the oxidant at 120 °C . Mechanistic studies and numerous efforts have been made to improve the efficiency of this “Shilov Chemistry”. − A large number of works on selective CH 4 oxidation have been focused on metal complexes, including precious metals such as Pt II , Pd II , Au III/I , and Ir III and main-group metals such as Hg II , Sb V , In III , Sn IV , Ti II , and Pb IV in strongly acidic media . A landmark work by Periana et al showed the conversion of CH 4 to methyl bisulfate, (CH 3 )­HSO 4 , as a primary product that was subsequently worked up by hydrolysis to produce CH 3 OH.…”

“…Although Shilov Chemistry is based on the Pt II catalyst, the isoelectronic structure of Au III and Pt II in the same d electronic configuration and the similar preference for square-planar complexes shared by Au III and Pt II suggest that Au complexes could be potential catalyst candidates for selective C–H activation in analogous to Shilov Chemistry. − The selective oxidation of CH 4 using H 2 SeO 4 as an oxidant with dissolved Au 0 and Au 2 O 3 as catalysts in concentrated H 2 SO 4 was reported with the highest TON of 32, producing (CH 3 )­HSO 4 with CO 2 as a minor byproduct . Shilov and co-workers reported the conversion of CH 4 to CH 3 OH catalyzed by Au complexes with rutin and quercetin ligands in the presence of NADH, by mimicking the function of aurophilic microbes. ,− Overall, in the reported Shilov Chemistry system and its analogues, the necessity of having oleum or high valent metal ions as oxidants in strongly acidic media, forming esters as the primary products, the difficulty in product separation and solvent recovery, reduced activity due to weakened acidity caused by water byproduct, strong corrosivity, and low CH 4 solubility in the acidic reaction media remain the common problems to be addressed in continued research. − …”