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Herein, the influence of group 1 and 2 metal cations on base-catalyzed dehydrogenative coupling of formate to form oxalate is reported. Treatment of sodium formate with a various types of bases (group 1 and 2 metal carbonates or metal hydroxides) revealed that, compared with carbonate salts, group 1 metal hydroxides behaved as efficient bases for the formation of oxalate, in which cesium hydroxide (CsOH) showed the best catalytic activity. DFT calculation for the reaction mechanism suggested that its kinetic advantage was generated from not only an increase of basicity but also destabilization of the intermediate species due to Na/Cs mixed cation system. The effect of cations in formate salts were also discussed both experimentally and theoretically, in which the yield of oxalic acid depended on thermodynamic stability of both products (oxalate salts) and intermediates.

Global iron and steel production continues to expand. The iron-making industry is, however, one of the main contributors to global warming due to its reliance on fossil fuel-based high temperature ...

The μ3-η2-iminoacyl-μ3-hexylidyne complex, [(Cp*Ru)3(μ3-CC5H11)(μ3-η2-HN═CMe)(μ-H)] (2a) (Cp* = η5-C5Me5), was prepared by the reaction of the μ3-η2:η2(⊥)-hexyne complex, [{Cp*Ru(μ-H)}3(μ3-η2:η2-nB...

Studies on the deactivation mechanism of the reaction of N,N-dialkylamides with TMDS catalyzed by Vaska’s complex, IrCl(CO)(PPh3)2 (1a), triggered the discovery of highly active Ir-PPh3 catalysts: photochemically activated 1a and thermally activated IrCl(PPh3)3 (8). Both catalysts showed excellent activity toward the selective conversion of a variety of N,N-dialkyl-, N-alkyl-N-aryl-, and N,N-diarylamides to the corresponding enamines with low catalyst loadings. The 14-electron species “ClIr(PPh3)2”, which is stabilized by solvents or reactants in the actual catalytic reactions, could be involved in the catalysis, which produces “HIr(PPh3)2” and “SiIr(PPh3)2” (Si = Me2HSiOMe2Si−) species in the catalytic cycle. An in situ generation method for the “ClIrL2” species was established by simply mixing [IrCl(η4-COD)]2 with PPh3 or other phosphorus ligands, which realized the facile large-scale syntheses of enamines.

Palladium-catalyzed reactions of dodecamethylcyclohexasilane [(SiMe2)6] (1) with alkynes led to efficient preparation of 1,1,4,4-tetramethyl-1,4-disilacyclohexadienes (3). The reactions were best catalyzed by Pd(0) species generated from Pd2(dba)3·CHCl3 and 1-isocyanoadamantane (AdNC). Terminal and internal alkynes bearing aryl and alkyl substituents could be used as substrates, and the reaction allowed gram-scale preparation of 3. A dimethylsilylene (Me2Si:) species, generated by activation of Si–Si bonds in 1 by Pd(0) species, was involved in the reaction mechanism. The DFT calculations suggest that oxidative addition of Si–Si bonds in 1 to Pd(CNAd)2 species is followed by extrusion of a Me2Si═Pd(CNAd) intermediate. Reaction of the resulting palladium-coordinated silylene with an alkyne forms a silacyclopropene, which dimerizes to give 3. The extrusion is accompanied by ring contraction of 1 to generate (SiMe2)5, which also contributes to formation of 3 and (SiMe2)4 by the Pd(0)-catalyzed reaction with ...

The appropriate design of a ligand (L) in IrCl(CO)(L)2 (4) realized the efficient synthesis of π-conjugated enamines possessing hole-transport properties. The iridium complex with electron-withdrawing phosphorus ligands catalyzed the hydrosilylation of amides to the corresponding silylhemiaminals, which were transformed to the enamines by heat or by treatment with acids. High catalytic efficiency (TON > 10,000) was achieved, which made it possible for the residual iridium in the enamine product to be below 20 ppb.

A triruthenium complex containing μ3-η2(∥)-ethyne and μ3-methylidyne ligands, (CpRu)3{μ3-η2(∥)-HC≡CH}(μ3-CH)(μ-H)2 (2a), was synthesized via the treatment of {Cp*Ru(μ-H)}3(μ3-H)2 (3) (Cp* = η5-C5Me5) with propene. In the low-temperature region, VT 1H NMR spectra showed that complex 2a is in equilibrium with a nonclassical μ3-vinyl complex, (CpRu)3(μ3-η2:η2-HC═CH2)(μ3-CH)(μ-H) (5a), which features an interaction between one of the β-vinyl protons and a Ru center. The presence of the unusual 3c-2e interaction of the β-C–H bond of the vinyl group is strongly supported by the small JC–H value (98 Hz) found for the β-carbon as well as the small JH–H value for the α-vinyl proton. Treatment of the equilibrated mixture of phenyl-substituted complexes (CpRu)3{μ3-η2(∥)-HC≡CPh}(μ3-CH)(μ-H)2 (2b) and (CpRu)3(μ3-η2:η2-HC═CHPh)(μ3-CH)(μ-H) (5b) with tBuNC afforded a μ-styryl complex, (CpRu)3(μ-η2-HC═CHPh)(μ3-CH)(μ-tBuNC)(μ-H) (6), while analogous treatment of 2a and 5a resulted in the formation of μ3-dimetalloallyl com...