Biphasic hydroformylation in new molten salts—analogies and differences to organic solvents

Stenzel, O.; Raubenheimer, Helgard G.; Esterhuysen, Catharine

doi:10.1039/b107720a

Cited by 38 publications

(21 citation statements)

References 55 publications

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“…None of the aminocarbene-borane adducts gave evidence of dissociation at ambient temperature. [179] [MeBF 3 ]K 157.5 [186] 107 163.5 [180] [PhBF 3 ]K 161 [187] 108 166.9 [180] 109 168.8 [181] 110 160.3 [182] [MeBH 3 ]Li 159.7 [188] 111 159.6 [183] [(tBu) 2 BH 2 ]K 164.3 [188] 118 159.6 [191] 120 164.5 [192] [Ph 4 B][NR 4 ] 164-165 [189] 121 163.4 [193] Ph 3 B-NR 3 162-164 [189] 125 162.3 [194] 163.2 [190] 127 163.3 [195] Borane adducts of phosphanylcarbenes proved to be less robust. The adduct 112, derived from a phosphanyl(silyl)-carbene, was observed by NMR spectroscopy at Ϫ80°C, but decayed rapidly due to elimination of Et 2 BNR 2 .…”

Section: Reverse Ylidesmentioning

confidence: 99%

Carbene Complexes of Nonmetals

Kirmse

2005

Eur J Org Chem

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Electrophilic carbenes accept a variety of n‐ and π‐donors. The products range from persistent ylides to matrix‐isolated xenon complexes. Ylides can be viewed as carbene complexes if they regenerate carbenes thermally or undergo concerted methylene transfer reactions. According to these definitions, the present review focuses on oxonium and iodonium ylides. Transient π‐complexes appear to be involved in addition reactions of carbenes with arenes (but not with alkenes). Nucleophilic carbenes form adducts with Lewis acids which are, for the most part, stable and have been well characterized structurally. Only recently attention has been directed to reversible systems. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

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Section: Reverse Ylidesmentioning

confidence: 99%

Carbene Complexes of Nonmetals

Kirmse

2005

Eur J Org Chem

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“…High conversions with varying linear/branched aldehyde ratios were observed. Compared to the conventional solvent toluene, similar turnover numbers, but a higher tendency toward isomerization and hydrogenation, were found [96].…”

Section: Supported Complexesmentioning

confidence: 80%

Carbonylation of Alkenes and Dienes

Kégl

2008

Modern Carbonylation Methods

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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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“…A polysilicate immobilized rhodium complex with ligand was found to perform as a selective hydroformylation catalyst showing an overall selectivity for the linear aldehyde of 94.6% in the case of 1-octene hydroformylation at 80 8C and 50 bar CO/H 2 1:1. In addition the formation of 1-nonanol (3.6% at 20% conversion) was observed via the hydrogenation of the corresponding aldehyde [13]. Functionalization of MCM-41 with 3-aminopropyltrimethoxyesiline (APTS), and subsequent encapsulation and anchoring of HRh(CO)(PPh 3 ) 3 in the mesoporous material was recently reported [4].…”

Section: Introductionmentioning

confidence: 94%

“…However, the small amount of the impregnated catalyst and probably the instability of the active rhodium intermediate species made the identification and the characterization of these species difficult. In order to improve the selectivity of the reaction, we have designed some experiments for which 10 mg of the catalyst Rh A 12MCM-M and 0.02-0.08 mmol PPh 3 were added in THF (Table 5, entries [13][14]. The conversions were low (45-53%).…”

Section: Rhodium(i) Supported Catalysts In the Heterogeneous Hydroformentioning

confidence: 99%