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TOF Values (tof + value)

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Chemistry	100%

Selected Abstracts

Very Fast Suzuki,Miyaura Reaction Catalyzed by Pd(OAc)2 under Aerobic Conditions at Room Temperature in EGME/H2O

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 1 2009
Alessandro Del Zotto
Abstract The results of a ligand-free Pd(OAc)2 -catalyzed Suzuki,Miyaura C,C coupling performed at room temperature under aerobic conditions are presented. It was found that the use of an ethylene glycol monomethyl ether/H2O mixture as the solvent resulted in very rapid reactions of aryl bromides with arylboronic acids. As a matter of fact, under optimized conditions, some substrates were converted quantitatively in less than 1 min with exceptionally high TOF values. For example, the reaction between 4-methoxyphenylboronic acid and bromobenzene afforded 4-methoxybiphenyl in 30 s with TOF = 180000 h,1. Furthermore, the reaction tolerates a wide range of functional groups and can be successfully applied to heteroaryl bromides such as 2-bromopyridine and 5-bromopyrimidine. Interestingly, also an activated aryl chloride such as 1-chloro-4-nitrobenzene reacted quantitatively with phenylboronic acid at 373 K. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

A Convenient and Efficient Rhenium-Catalyzed Hydrosilylation of Ketones and Aldehydes

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2009
Hailin Dong
Abstract The easily available rhenium(I) complex [Re(CH3CN)3Br2(NO)] catalyzes the homogeneous hydrosilylation of a great variety of organic carbonyl compounds (ketones and aldehydes). The reaction is quite sensitive to the solvent applied. Chlorobenzene was found to be superior over all the other solvents used. Various aliphatic and aromatic silanes were tested. Excellent yields were achieved at 85,°C in chlorobenzene using triethylsilane, the reaction affording TOF values of up to 495,h,1. A possible reaction mechanism for the hydrosilylation is presented. [source]

Decomposition of Formic Acid Catalyzed by a Phosphine-Free Ruthenium Complex in a Task-Specific Ionic Liquid

CHEMCATCHEM, Issue 10 2010
Jackson D. Scholten
Abstract The dehydrogenation of formic acid is effectively catalyzed by the Ru complex [{RuCl2(p -cymene)}2] dissolved in the ionic liquid (IL) 1-(2-(diethylamino)ethyl)-3-methylimidazolium chloride at 80,°C without additional bases. This catalytic system gives TOF values of up to 1540,h,1. Preliminary kinetic insights show formal reaction orders of 0.70(±0.15), 0.78(±0.03) and 2.00(±0.17) for the Ru catalyst, IL,1, and formic acid, respectively. The apparent activation energy of this process is estimated to be (69.1±7.6),kJ,mol,1. In addition, dimeric Ru hydride ionic species involved in the reaction, such as [{Ru(p -cymene)}2{(H),-(H)-,-(HCO2)}]+ and [{Ru(p -cymene)}2{(H),-(Cl),-(HCO2)}]+, are identified by mass spectrometry. The presence of water in large amounts inhibits higher conversions. Finally, a remarkable catalytic activity is observed during recycles, indicating this system's potential for hydrogen gas production. [source]

Mechanistic Insights into Acetophenone Transfer Hydrogenation Catalyzed by Half-Sandwich Ruthenium(II) Complexes Containing 2-(Diphenylphosphanyl)aniline , A Combined Experimental and Theoretical Study

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 28 2008
Alessia Bacchi
Abstract Several new half-sandwich ruthenium(II) complexes containing 2-(diphenyphosphanyl)aniline (PNH2) of formula {Ru[(,2P,N)PNH2](p -cymene)Cl}Y [Y = Cl (1a), PF6 (1b), BF4 (1c), BPh4 (1d), TfO (1e)] were synthesized and fully characterized both in solution (1H NMR and 31P{1H} NMR spectroscopy) and in the solid state (FTIR, X-ray analysis on single crystal). Complexes 1a and 1b are active precatalysts in the hydrogen transfer reaction of acetophenone, leading to tof values up to 4440 h,1. In comparison, the {Ru[(,2P,N)PNMe2](p -cymene)Cl}Cl complex leads to a tof value of 100 h,1 under the same catalytic conditions. The mechanism through which the precatalysts operate was deeply explored by high-resolution MS (ESI) and DFT/PCM studies. The results reveal that the complexes containing PNH2 operate through a bifunctional mechanism analogous to that proposed for diamines and amino alcohol ligands. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]