111-67-1Relevant articles and documents
Olefin isomerization by iridium pincer catalysts. experimental evidence for an η3-allyl pathway and an unconventional mechanism predicted by DFT calculations
Biswas, Soumik,Huang, Zheng,Choliy, Yuriy,Wang, David Y.,Brookhart, Maurice,Krogh-Jespersen, Karsten,Goldman, Alan S.
, p. 13276 - 13295 (2012)
The isomerization of olefins by complexes of the pincer-ligated iridium species (tBuPCP)Ir (tBuPCP = κ3-C 6H3-2,6-(CH2PtBu2) 2) and (tBuPOCOP)Ir (tBuPOCOP = κ3-C6H3-2,6-(OPtBu 2)2) has been investigated by computational and experimental methods. The corresponding dihydrides, (pincer)IrH2, are known to hydrogenate olefins via initial Ir-H addition across the double bond. Such an addition is also the initial step in the mechanism most widely proposed for olefin isomerization (the "hydride addition pathway"); however, the results of kinetics experiments and DFT calculations (using both M06 and PBE functionals) indicate that this is not the operative pathway for isomerization in this case. Instead, (pincer)Ir(η2-olefin) species undergo isomerization via the formation of (pincer)Ir(η3-allyl)(H) intermediates; one example of such a species, (tBuPOCOP) Ir(η3-propenyl)(H), was independently generated, spectroscopically characterized, and observed to convert to ( tBuPOCOP)Ir(η2-propene). Surprisingly, the DFT calculations indicate that the conversion of the η2-olefin complex to the η3-allyl hydride takes place via initial dissociation of the Ir-olefin π-bond to give a σ-complex of the allylic C-H bond; this intermediate then undergoes C-H bond oxidative cleavage to give an iridium η1-allyl hydride which "closes" to give the η3-allyl hydride. Subsequently, the η3-allyl group "opens" in the opposite sense to give a new η1-allyl (thus completing what is formally a 1,3 shift of Ir), which undergoes C-H elimination and π-coordination to give a coordinated olefin that has undergone double-bond migration.
Rh(i) complexes supported on a biopolymer as recyclable and selective hydroformylation catalysts
Makhubela, Banothile C. E.,Jardine, Anwar,Smith, Gregory S.
, p. 338 - 347 (2012)
Chitosan-supported Rh complexes were prepared in a stable form to form new catalysts and have been characterized using elemental analysis, UV-vis, FT-IR, ICP-MS, PXRD, solid state 31P and 13C NMR spectroscopy and TEM. Mononuclear Rh(i) complexes (as models for the heterogenized catalysts) were also prepared via the Schiff-base condensation reaction and the crystal structure of the cyclohexyl iminophosphine Rh(i) complex was elucidated. The chitosan-supported Rh complexes and mononuclear analogues are active catalysts in the hydroformylation of 1-octene with optimal reaction conditions realized at 75 °C and 30 bar syngas pressure. Under these conditions, 1-octene conversion to the desired linear aldehydes was observed and the best selectivity in this regard was shown by the supported iminophosphine-based rhodium catalyst. Overall, the supported catalysts showed similar chemo- and regioselectivities in comparison to their mononuclear counterparts but where more stable, being reused up to four times without loss of activity and selectivity.
Activation of tetrabutylammonium hydrogen difluoride with pyridine: A mild and efficient procedure for nucleophilic fluorination
Moughamir, Khadija,Atmani, Aziz,Mestdagh, Helene,Rolando, Christian,Francesch, Charlette
, p. 7305 - 7306 (1998)
The nucleophilic fluorination of alkyl iodides, bromides and tosylates and of α-bromo- or α-chloroketones is smoothly effected by tetrabutylammonium hydrogen difluoride in the presence of pyridine, in dioxane or THF, with good or satisfying substitution-to-elimination ratio.
Impact of Alkali and Alkali-Earth Cations on Ni-Catalyzed Dimerization of Butene
Ehrmaier, Andreas,L?bbert, Laura,Sanchez-Sanchez, Maricruz,Bermejo-Deval, Ricardo,Lercher, Johannes
, p. 3705 - 3711 (2020)
The presence of alkali (Na+ or Li+) or alkali-earth (Ca2+ or Mg2+) cations adjusting the acid-base properties on amorphous silica-alumina influences markedly the catalytic properties of supported Ni for 1-butene dimerization. The low concentration of Br?nsted acid sites on these catalysts reduces the double bond isomerization of butene and inhibits the formation of dimethylhexene as primary product. While the alkali and alkali-earth cations act as weak Lewis acid sites, only Ni2+ sites are catalytically active for dimerization of 1-butene. n-Octene and methylheptene are formed selectively as primary products; dimethylhexene is a secondary product. The open environment of the Ni2+ sites does not induce different reaction pathways compared to Ni2+ in the pores of zeolites.
Indenyl- and fluorenyl-functionalized n-heterocyclic carbene complexes ofrhodium and iridium synthetic, structural and catalytic studies
Downing, Stephen P.,Pogorzelec, Peter J.,Danopoulos, Andreas A.,Cole-Hamilton, David J.
, p. 1816 - 1824 (2009)
Rhodium and iridium complexes with N-heterocyclic carb-enes (NHC) functionalized with neutral or anionic indenyland fluorenyl groups are reported. In the complexes the li-gands adopt monodentate, bidentate or bridging bondingmodes with the NHC group ?-bonded and the fluorenyl orindenyl functionalities either dangling or coordinated to themetal with various hapticities (?1, ?3 and ?5). Metallation ofthe C-H bond of the alkylene linker in the ligand has also been observed. Catalytic studies on the bidentate RhIcom-plex 6 show that it is weakly active for the hydroformylationof 1-octene with poor linear selectivity, but it shows slightlylower activity than the standardMonsanto system for the car-bonylation of methanol. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009.
Synthesis of the deuterated sex pheromone components of the grape borer, xylotrechus pyrrhoderus
Kiyota, Ryutaro,Yamakawa, Rei,Iwabuchi, Kikuo,Hoshino, Keita,Ando, Tetsu
, p. 2252 - 2256 (2009)
Adult males of the grape borer, Xylotrechus pyrrho- derus, secrete (S)-2-hydroxy-3-octanone [(S)-1] and (2S,3S)-2,3-octanediol [(2S,3S)-2] from their nota of prothoraces as sex pheromone components. Their structural similarity suggests that one of them is the biosynthetic precursor of the other component. In order to confirm the biochemical conversion, deuterated derivatives of both components were synthesized by starting from a Wittig reaction between hexanal and an ylide derived from D5-iodoethane and ending with enantiomeric resolution by chiral HPLC. The molecular ions of 1 and 2 could scarcely be detected by using a GC- MS analysis, and the labeled compounds showed similar mass spectra to the unlabeled pheromone components. However, several fragment ions, including four deuterium atoms, were observed in the mass spectra of their acetate derivatives, indicating that the conversion could be confirmed by examining a compound with the diagnostic ions after acetylation of the volatiles collected from insects treated with the labeled precursors.
POLYMER-SUPPORTED 2,2'-DIPYRIDYLMETHANE: SYNTHESIS AND FORMATION OF TRANSITION METAL COMPLEXES
Elman, Bjoern,Moberg, Christina
, p. 117 - 122 (1985)
The chelating ligand 2,2'-dipyridylmethane can be anchored to styrene-divinylbenzene polymers by reaction of the anion of 2,2'-dipyridylmethanol with chloromethylated or chloroacetylated resins under mild conditions.A number of transition metal complexes of the polymeric ligand have been prepared.Alkenes and alkynes are readily hydrogenated with the Pd(OAc)2 complex of the polymeric ligand as catalyst.
Hydroformylation in fluorous solvents
Foster, Douglas F.,Adams, Dave J.,Gudmunsen, David,Stuart, Alison M.,Hope, Eric G.,Hamilton, David J.
, p. 722 - 723 (2002)
Triaryl-phosphines and -phosphites bearing fluorous ponytails give high rates, good linear selectivity and good retention of catalyst in the fluorous phase during hydroformylation of alkenes in fluorous solvents.
Studies on organolanthanide complexes. XLI. Cata;ytic isomerization of olefins by organolanthanide complex/sodium hydride systems
Qian, Changtao,Zhu, Dunming,Li, Dongmei
, p. 175 - 180 (1992)
Isomerization of several 1-alkenes catalyzed by organolanthanide complex/sodium hydride systems in THF at 45 deg C, affords cis- and trans-2-alkenes in excellent yields.Effects of solvent and ?-ligand of complex on this isomerization are also examined.The catalytic isomerization may occur via organolanthanide hydride intermediate.
Comparative Dimerization of 1-Butene mith a Variety of Metal Catalysts, and the Investigation of a New Catalyst for C-H Bond Activation
Small, Brooke L.,Schmidt, Roland
, p. 1014 - 1020 (2004)
Catalytic dimerization of 1-butene by a variety of catalysts is carried out, and the products are analyzed by gas chromatography and mass spectrometry. Catalysts based on cobalt and iron can produce highly linear dimers, with the cobalt-based dimers exceeding 97% linearity. Catalysts based on vanadium and aluminum prefer to make branched dimers, which are most often methyl-heptenes in the case of vanadium and almost exclusively 2-ethyl-1-butene in the case of aluminum. The vanadium catalyst also produces substantial amounts of dienes and alkanes, suggesting a competing hydrogenation/dehydrogenation pathway that appears to involve vinyl C-H bond activation. Nickel catalysts are generally less selective than those based on iron or cobalt for making linear dimers, but they can make dimers with 60% linearity. The major by-products for the nickel systems are trisubstituted internal olefins. An important side reaction that must be considered for dimerization reactions is 1-butene isomerization to 2-butene, which makes recycling the butene difficult for a linear dimerization process. Aluminum, iron, and vanadium systems promote very little isomerization, but nickel and cobalt systems tend to isomerize the undimerized substrate heavily.
