Alkenes rhodium

The nature of the oxidation products is traceable to the nature of the rhodium-alkene interaction. Terminal alkenes and internal ones (e.g. cycloheptene), which form 77-complexes of rhodium(I), e.g. [RhCl(alkene)2]2, are selectively converted into methyl ketones, whereas alkenes which form 7r-allylic complexes of rhodium(III) (e.g. cyclopen-tene) give alkenyl ethers via oxidative substitution of the alkene by the solvent alcohol.204... 

Indenyl-fluorenyl systems, propylene polymerization, 4, 1068 Indenylidenes, in ROMP initiation, 11, 633 7]5-Indenyl ligand, in molybdenocene dihalides, 5, 573 Indenyl ligands, in cobalt(III) complexes, 7, 20 7]5-Indenyl ligands, in rhodium alkene complexes, 7, 197 2-(Indenyl)—phenoxo complexes, with mono-Cp Ti(IV),... 

The mechanism of asymmetric hydrogenation of dehydroaminoacids has been studied by a combination of kinetic and spectroscopic methods, mainly by Halpern et al. [38] and Brown et al. [39]. It was proved that the substrate bound by both the double bond and the amide group. It was surprising to see that the major diastereomeric rhodium-alkene complex detected in solution was the less reactive one towards hydrogen. This showed the inaccuracy of previous models of the lock and key type between the prochiral double bond and the chiral... 

Dubbaka and Vogel reported on rhodium-catalysed Mizoroki-Heck-type reactious employing arenesulfonyl chlorides as inexpensive electrophiles. Thereby, styrene derivatives were arylated under base-free conditions. Again, rhodium-alkene complex 89 was found to be significantly more active than phosphine-derived rhodium species (Scheme 10.32) [60],... 

The complex between the rhodium and the alkene is called a complex. In it, two electrons are donated by the alkene to the rhodium. Alkenes are often called tt donors to distinguish them from tr donors such as PhaP , Cl , and so on. 

The X-ray crystal structure of [Rh( n -CsH4Ph)( n -C2H4)2] has been reported and the conformation discussed in terms of CNDO-MO calculations. A series of rhodium-alkene complexes ctnitaining the potentially bidentate phosphine ligands [Pr P(CH2)nX] (n >2,3, X > NMe2 n>2, X > OMe) have been synthesised and characterised. Reaction of [RhCl(ri -... 

Thus, the relative reactivity is ptrallel to the order of rhodium/alkene complex stability and the insertion rate whidi can be estimated by the LUMO oiersy level of alkenes. Howeva, the additions to trisubstituted unsaturated ketones and esters are significantly slow. The rhodium oanplexes catalyze a similar reaction of 1-alkenylboronic acids, but all attempts at the addition of alkylboronic acids or trialkylboranes having a P-hydrogen are unsuccessful. 

Cationic rhodium complexes catalyse the oxidative anti-Markovnikov amination of aromatic alkenes to enamines, a process that is accompanied by a simultaneous formation of 1 equiv. of ethylbenzene. Kinetic and mechanistic studies reveal that the yield and the rate of the reaction increase on increasing the styrene amine ratio. Furthermore, the type of phosphine ligand greatly influences the reaction. The formation of cationic rhodium-alkene-amine complexes has been proposed to be the first step towards the active catalytic species. ... 

The compound Rh(acac)(coe)2 is long known, but a new synthetic protocol from [Rhl/t-ClXcoelzlz with Na(acac) (without the use of a thallium salt) was reported and the crystal structure of the compound was determined by X-ray diffraction studies. The thermal reaction of Rh(acac)(CO)2 with alkenes was studied and a series of rhodium alkene complexes, Rh(acac)(CO)(alkene) (alkene = ethylene, 1-propene, 1-octene), were characterized. The catalytic... 

C2.7.6.1 WILKINSON HYDROGENATION OF ALKENES CATALYSED BY A RHODIUM COMPLEX... 

Halpern J, Okamoto T and Zakhariev A 1976 Mechanism of the chlorotris(triphenylphosphine)rhodium(l)-catalyzed hydrogenation of alkenes J. Mol. Catal. 2 65-9... 

The uncatalyzed addition of hydrogen to an alkene although exothermic is very slow The rate of hydrogenation increases dramatically however m the presence of cer tain finely divided metal catalysts Platinum is the hydrogenation catalyst most often used although palladium nickel and rhodium are also effective Metal catalyzed addi tion of hydrogen is normally rapid at room temperature and the alkane is produced m high yield usually as the only product... 

Alkenes react with hydrogen in the presence of a platinum palladium rhodium or nickel catalyst to form the corresponding alkane... 

The conditions for hydrogenation of alkynes are similar to those employed for alkenes In the presence of finely divided platinum palladium nickel or rhodium two molar equivalents of hydrogen add to the triple bond of an alkyne to yield an alkane... 

Hydrogenation of benzene and other arenes is more difficult than hydrogenation of alkenes and alkynes Two of the more active catalysts are rhodium and platinum and it IS possible to hydrogenate arenes m the presence of these catalysts at room temperature and modest pressure Benzene consumes three molar equivalents of hydrogen to give cyclohexane... 

The stereospecific polymerization of alkenes is catalyzed by coordination compounds such as Ziegler-Natta catalysts, which are heterogeneous TiCl —AI alkyl complexes. Cobalt carbonyl is a catalyst for the polymerization of monoepoxides several rhodium and iridium coordination compounds... 

Olefin isomerization can be catalyzed by a number of catalysts such as molybdenum hexacarbonyl [13939-06-5] Mo(CO)g. This compound has also been found to catalyze the photopolymerization of vinyl monomers, the cyclization of olefins, the epoxidation of alkenes and peroxo species, the conversion of isocyanates to carbodiimides, etc. Rhodium carbonylhydrotris(triphenylphosphine) [17185-29-4] RhH(CO)(P(CgH )2)3, is a multifunctional catalyst which accelerates the isomerization and hydroformylation of alkenes. 

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