Hydroformylation of 1-octene using rhodium-1,3-R2-3,4,5,6-tetrahydropyrimidin-2-ylidenes (R=2-Pr, mesityl)

Bortenschlager, Martin; Mayr, Monika; Nuyken, Oskar; Buchmeiser, Michael R.

doi:10.1016/j.molcata.2005.02.005

Cited by 39 publications

(24 citation statements)

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“…First the COD-ligand is substituted by CO. Second the rhodiumhydrido-complex, the active species, is formed by an oxidative addition of hydrogen and a consecutive reductive elimination of HX. During the whole process, the rhodium-NHC-bond remains stable as successfully has been shown by several groups [12,13,16]. Complex 7 has been investigated by 13 C NMR after 20 h hydroformylation (100°C, 50 bar CO/H 2 ).…”

Section: Resultsmentioning

confidence: 67%

“…Catalysts 5-8 have been investigated under the same reaction conditions and activities were calculated in all cases from the point of inflection in the slope of aldehyde formation. As has been shown recently neither the cyclooctadiene (COD) nor the halide has any influence on the results of the hydroformylation of 1-octene (Table 1, entries 1-4) [13]. In all cases, the catalytically active species is supposed to be a Rh(NHC)-carbonyl-hydrido-complex which is formed in situ under hydroformylation conditions analogous to the Wilkinson-catalyst [19] (Fig.…”

Section: Resultsmentioning

confidence: 85%

“…1) have been characterized with regard to their catalytic activity and selectivity of the hydroformylation of 1-octene. The results have been compared to that of the recently published tetrahydropyrimidine-based NHC-complexes (1-4) [13]. The synthesis and structural data of the rhodium-NHCcomplexes presented here have already been published elsewhere by Buchmeiser and Herrmann, respectively [17,18].…”

Section: Resultsmentioning

confidence: 98%

“…Both parameters are determined by the attached NHC-ligand only. The activity and selectivity of catalysts 1-4 was recently studied in our group [13]. Catalysts 5-8 have been investigated under the same reaction conditions and activities were calculated in all cases from the point of inflection in the slope of aldehyde formation.…”

Section: Resultsmentioning

confidence: 99%

“…Recently, it could even be shown that rhodium-NHC-bonds remain stable under hydroformylation conditions (CO/H 2 -pressure: up to 50 bar, temperature up to 100°C) [12,13], meaning that CO is not able to substitute NHC-ligands in rhodium-NHC complexes. Therefore, rhodium-NHCcomplexes should be well suitable as catalysts for hydroformylation, even in aqueous systems, as has been repeatedly proven [12][13][14][15]. More recently, we demonstrated the first successful aqueous biphasic hydroformylation of 1-octene with a NHC/rhodium catalyst when immobilized to an amphiphilic polymer [16].…”

Section: Introductionmentioning

confidence: 99%

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Rhodium–NHC-complexes as potent catalysts in the hydroformylation of 1-octene

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Section: Resultsmentioning

confidence: 67%

Section: Resultsmentioning

confidence: 85%

Section: Resultsmentioning

confidence: 98%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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In the beginning, only cobalt catalysts were utilized for hydroformylation under relatively vigorous conditions. The moderate selectivity of the generally more desired linear isomers, the substantial formation of by-products, and the low stability of the catalysts forced more appropriate catalytic systems to be developed. Using donor ligands such as phosphanes resulted in an increase in the linear selectivity. Rhodium-containing catalysts, however, permitted the use of much milder conditions in combination with suitable ligands. Other transition metals such as ruthenium, palladium, platinum, and iridium also tended to show activity for hydroformylation, albeit a vast majority of works on hydroformylation still concentrated on rhodium-containing systems. Cobalt CatalystsThe initial rate of Co 2 (CO) 8 -catalyzed cyclohexene hydroformylation, triethyl orthoformate carbonylation, and CoH(CO) 4 formation from Co 2 (CO) 8 and H 2 is reduced by the addition of dinitrogen, argon, or xenon. It is assumed that the additional gas competes with one or more reactants for a coordinatively unsaturated site responsible for their activation, thus affecting the reaction rate [1].The carbonylation reaction of propylene oxide in the presence of various [Lewis acid] þ [Co(CO) 4 ] À salts was investigated using in situ attenuated total reflection infrared (ATR-IR) spectroscopy. b-Alkoxy-acyl-cobalttetracarbonyl species were found to be key intermediates from which two reaction routes start depending on the applied Lewis acid. Labile Lewis acid-alkoxy combinations primarily favor the production of lactone products [2].The reaction of olefins (1-octene, 3,3-dimethylbutene, cyclohexene) introduced into a preequilibrated Co 2 (CO) 8 þ H 2 system was investigated by high-pressure infrared spectroscopy. Based on the observed induction period for the formation of the corresponding aldehyde, the decrease in HCo(CO) 4 concentration and increase in Co 2 (CO) 8 concentration during the induction period, the active catalytic species of the type H x Co y (CO) z was proposed [3]. Experiments with isotope mixtures of H 2 /D 2 in the gas phase during the various steps of the reaction showed that the ratio of H/D isotopes in the hydrocarbon portion of the aldehyde product correlates with the HCo(CO) 4 /DCo(CO) 4 ratio in solution, whereas the RC(¼O)H/RC(¼O)D product ratio correlates with the H 2 /D 2 in the gas phase. It was concluded that the dominant pathway for the hydrogenolysis step in this type of hydroformylation is the direct reaction of hydrogen or deuterium with the acyl complex intermediate [4].The effect of argon (280 bar) on the rate of aldehyde formation in 1-hexene hydroformylation catalyzed by Co 2 (CO) 8 at 50 C, 70 bar P(CO) and 85 bar P(H 2 ) in toluene was investigated by high-pressure FT-IR spectroscopy. The initial rate of the reaction was found to be reduced by the presence of argon. A similar effect was observed in the RhH(CO)(PPh 3 ) 3 -catalyzed cyclohexene hydroformylation reaction [5]. 162j 7 Carbonylation of Alkenes and D...

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Hydroformylation of 1-octene using rhodium-1,3-R2-3,4,5,6-tetrahydropyrimidin-2-ylidenes (R=2-Pr, mesityl)

Cited by 39 publications

References 45 publications

Rhodium–NHC-complexes as potent catalysts in the hydroformylation of 1-octene

Rhodium–NHC-complexes as potent catalysts in the hydroformylation of 1-octene

Natural Products

Carbonylation of Alkenes and Dienes

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