Homogeneous Transition Metal Catalysis Research Articles

Cyclovoltammetric studies on the dimerization of methyl acrylate by ruthenium complexes

Electrochemical measurements are described on transition metal complexes which are or might be catalyst precursors for the tail-to-tail dimerization of methyl acrylate (MA). Thus, RuH 2(PPh 3) 4 and RuHCl(CO)(PPh 3) 3 are studied electrochemically by cyclic voltammetry (CV) in various solvents including neat MA. It is shown that the activation of the catalyst precursor RuH 2(PPh 3) 4 with trifluoromethanesulfonic acid and of RuHCl(CO)(PPh 3) 3 with triethyloxonium tetrafluoroborate generates new complexes that are easy to reduce and rather difficult to oxidize. The electrochemical measurements provide information on the deactivation of the catalyst. CpRuH(PPH 3) 2, which can easily be oxidized but can not be reduced, even at −2.5 V versus SCE, does not act as a catalyst precursor neither in pure form nor in the presence of activating compounds. The ease of reduction or oxidation seems to be connected to a possible catalytic activity. It is, therefore, postulated that cyclic voltammetry can be a useful tool in the study of homogeneous transition metal catalysis.

Dimerization of methyl acrylate by homogeneous transition metal catalysis. Part II. Activation of dihydridoruthenium(II) phosphane complexes by CF 33H

The tail-to-tail dimerization of methyl acrylate (MA) in the presence of H 2Ru(PPh 3) 4 ( 1) or H 2(CO)Ru(PPh 3) 3 ( 2) and CF 3SO 3H to give a mixture of linear dimers is described. In neat methyl acrylate at 85°C the reaction shows turnover numbers of 300 in 20 h and 640 in 7 d. Mechanistic studies show that the initial step of the reaction is the reduction of H 2Ru(PPh 3) 4 ( 1) by MA to form Ru(MA) 2 (PPh 3) 2 ( 5). After activation with CF 3SO 3H the catalytically active species contains only one phosphane ligand. The basic mechanistic features of the dimerization reaction have been revealed by 2H NMR spectroscopy involving the use of CF 3SO 3D. The deuterium-labelling studies indicate the intermediate formation of a ruthenium(II) hydride complex. Subsequent olefin insertions in this complex, followed by β-hydride elimination,lead to the linear dimeric products.

Dimerization of methyl acrylate by homogeneous transition-metal catalysis. Part I. Activation of hydrido (carbonyl) chloro-[bis(triisopropylphosphane)] ruthenium by CF 3SO 3Ag

The dimerization of methyl acrylate in the presence of RuH(CO)Cl[P(i-Pr) 3] 2 and CF 3SO 3Ag to a mixture of linear tail-to-tail dimers is described. The mixture consists of 90% trans-2-hexene-1,6-dioic acid dimethyl ester, of 6% cis-2-hexene-1,6-dioic acid dimethyl ester and of 3% trans-3-hexene-1,6-dioic acid dimethyl ester. The reaction is carried out in neat methyl acrylate at 85°C and displays turnover numbers of 600.

Nickel: An Element with Wide Application in Industrial Homogeneous Catalysis

AbstractThe efficiency and future development of the chemical industry are closely linked to catalysis. It has been estimated, for example, that 60 to 70% of all industrial chemicals have involved the use of a catalyst at some point during their manufacture. In the past two decades the share of the market credited to homogeneous transition metal catalysis increasead to 10–15%. Besides cobalt, which is used mainly in hydroformylation reactions, nickel is the most frequently used metal. Many carbon–carbon bond formation reactions can be carried out with high selectivity if catalyzed by organonickel complexes. Such reactions include, inter alia, carbonylation reactions, cyclic and linear oligomerization and polymerization reactions of monoenes and dienes, and hydrocyanation reactions. It was Reppe and Wilke who pioneered and shaped the field of homogeneous nickel catalysis. Great impetus was also given to the development of organonickel chemistry by Wilke and his students. Research in this area has contributed immensely towards an understanding of the reactions involved in catalysis.—This review is primarily concerned with nickel‐catalyzed reactions which are of interest both preparatively and industrially; some mechanistic aspects are also dealt with.

Homogeneous transition-metal catalysis. Cleavage of the CN bond of tertiary amines by acid anhydrides in the presence of transition metal ions

Abstract In the presence of transition metal chlorides, acid anhydrides are highly active in promoting the dealkylation of tertiary amines, and good yields of N , N -dialkylamides are obtained.

ChemInform Abstract: CONTROLLING FACTORS IN HOMOGENEOUS TRANSITION METAL CATALYSIS. CONTROL OF METAL‐CATALYZED REACTIONS. PART XII

Chemischer InformationsdienstVolume 12, Issue 1 Reviews ChemInform Abstract: CONTROLLING FACTORS IN HOMOGENEOUS TRANSITION METAL CATALYSIS. CONTROL OF METAL-CATALYZED REACTIONS. PART XII P. HEIMBACH, P. HEIMBACHSearch for more papers by this authorH. SCHENKLUHN, H. SCHENKLUHNSearch for more papers by this author P. HEIMBACH, P. HEIMBACHSearch for more papers by this authorH. SCHENKLUHN, H. SCHENKLUHNSearch for more papers by this author First published: January 6, 1981 https://doi.org/10.1002/chin.198101365AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume12, Issue1January 6, 1981 RelatedInformation

Separation of Steric and Electronic Effects in the Reaction Enthalpies of Association of Phosphorus Ligands

An understanding of the directing influence of Lewis bases in homogeneous transition metal catalysis is brought nearer by data characterizing the metal-ligand bond. The enthalpy of reaction of (1) with L was measured for 22 phosphorus ligands L and resolved into “steric” and “electronic” components.

The stereochemistry of the silicon-cobalt bond and some implications for homogeneous transition-metal catalysis

The stereochemistry of the silicon-cobalt bond and some implications for homogeneous transition-metal catalysis