T:Toxic;591-78-6Relevant articles and documents
Investigation of the Wacker Process in Formamide Microemulsions
Rico, I.,Couderc, F.,Perez, E.,Laval, J. P.,Lattes, A.
, p. 1205 - 1206 (1987)
Formamide microemulsions have been used as reaction media for the Wacker process, giving much faster oxidation of hex-1-ene to hexan-2-one than in classical media.
Specific Oxidation of 2 by O2 via the Coordination of in Situ Generated HOOH. Implications for the Rh(III)/Cu(II)-Catalyzed O2 Oxidation of 1-Alkenes to 2-Ketones
Nyberg, Eric D.,Pribich, David C.,Drago, Russell S.
, p. 3538 - 3544 (1983)
The oxidation of 1-hexene to 2-hexanone catalyzed by Rh(III)/Cu(II) mixtures is investigated.In order to study the reactions that rhodium undergoes to form an active catalyst, 2 (A) is used as a catalyst precursor.A number of results are obtained that indicate that this species must be converted to a rhodium(III) complex before catalysis occurs.With A as a catalyst precursor in the absence of Cu(II), long induction are observed for catalytic oxidations.Rhodium(I) is oxidized to rhodium(III) chloride during the induction period.Furthermore, at higher chloride/rhodium ratios (up to a 10:1 mole ratio), greater initial rates and catalyst stabilities are found.These observations are used as partial justification for characterizing rhodium(III) as an active catalyst in the oxidation of 1-hexene to 2-hexanone.The oxidation of 2 to rhodium(III) chloride is investigated in detail.An unusual mechanism for this reaction is proposed.Hydrogen peroxide, produced in situ from the reduction of O2 by alcohol solvent, oxidizes 2.An intermediate hydroperoxide complex is formed in the course of the oxidation to rhodium(III) which contains a coordinated carbonyl ligand (B).This intermediate is studied in dilute solution and is found to decompose immediately when attempts are made to isolate it.Very few stable hydroxyperoxide and alkylperoxide complexes of the platinum metals have been reported; some are capable of oxidizing terminal olefins to 2-ketones.In contrast, the oxidation of 2 to rhodium(III) chloride under identical conditions is much faster and proceeds by a mechanism avoiding detectable quantities of this hydroperoxo intermediate, while 2 is not oxidized even after 48 h.The oxidation of A to B occurs only in solvents capable of reducing O2.
New insight into the mechanism of the reaction between α,β-unsaturated carbonyl compounds and triethylborane (Brown's reaction)
Beraud, Valérie,Gnanou, Yves,Walton, John C.,Maillard, Bernard
, p. 1195 - 1198 (2000)
A study of the reaction of α,β-unsaturated carbonyl compounds with triethylborane under free radical conditions (Brown's reaction) including spectroscopic analyses (11B NMR, IR, EPR) of products and intermediates indicated that these reactions involve the prior formation of an 'α,β- unsaturated carbonyl compound-organoborane' complex. (C) 2000 Elsevier Science Ltd.
Activation of Molecular Hydrogen and Oxygen by PSiP Complexes of Cobalt
Murphy, Luke J.,Ruddy, Adam J.,McDonald, Robert,Ferguson, Michael J.,Turculet, Laura
, p. 4481 - 4493 (2018)
The syntheses of CoII halide complexes supported by κ3-(2-Cy2PC6H4)2SiMe (Cy-PSiP) ligation are detailed. Reduction of (Cy-PSiP)Co(PMe3)I could be achieved under mild conditions using magnesium metal to generate the CoI complex (Cy-PSiP)Co(PMe3)N2 in high yield. When this reaction was carried out under an atmosphere of CO, (Cy-PSiP)Co(CO)2 was obtained. Unlike the facile reduction of CoII to CoI, attempts to access CoIII species supported by Cy-PSiP ligation proved challenging. Attempted oxidative addition reactions involving (Cy-PSiP)Co(PMe3)N2 were generally unsuccessful, with the sole exception of H2, which reacted to afford the dihydride complex (Cy-PSiP)Co(PMe3)(H)2. The dihydride complex undergoes Co-H site exchange in solution and readily eliminates H2. The CoI precursor (Cy-PSiP)Co(PMe3)N2 is a competent precatalyst for the hydrogenation of terminal alkenes. Exposure of (Cy-PSiP)CoI to O2 gas under anhydrous conditions led to rapid ligand oxidation at Si and P, with no evidence observed at low temperature for a CoIII superoxo or peroxo intermediate. Exclusive oxidation at Si to afford a CoII-siloxy complex was observed upon treatment of (Cy-PSiP)CoI with one equiv. Me3NO. While this siloxy complex did not react further with O2, treatment with a second equiv. of Me3NO led to subsequent oxidation involving one phosphino donor. This observation supports the notion that in the ligand oxidation reactivity observed with O2, the O atoms incorporated at both Si and P are likely derived from the same O2 molecule.
Mechanisms for High Selectivity in the Hydrodeoxygenation of 5-Hydroxymethylfurfural over PtCo Nanocrystals
Luo, Jing,Yun, Hongseok,Mironenko, Alexander V.,Goulas, Konstantinos,Lee, Jennifer D.,Monai, Matteo,Wang, Cong,Vorotnikov, Vassili,Murray, Christopher B.,Vlachos, Dionisios G.,Fornasiero, Paolo,Gorte, Raymond J.
, p. 4095 - 4104 (2016)
Carbon-supported, Pt and PtCo nanocrystals (NCs) with controlled size and composition were synthesized and examined for hydrodeoxygenation (HDO) of 5-hydroxymethylfurfural (HMF). Experiments in a continuous flow reactor with 1-propanol solvent, at 120 to 160 °C and 33 bar H2, demonstrated that reaction is sequential on both Pt and PtCo alloys, with 2,5-dimethylfuran (DMF) formed as an intermediate product. However, the reaction of DMF is greatly suppressed on the alloys, such that a Pt3Co2 catalyst achieved DMF yields as high as 98%. XRD and XAS data indicate that the Pt3Co2 catalyst consists of a Pt-rich core and a Co oxide surface monolayer whose structure differs substantially from that of bulk Co oxide. Density functional theory (DFT) calculations reveal that the oxide monolayer interacts weakly with the furan ring to prevent side reactions, including overhydrogenation and ring opening, while providing sites for effective HDO to the desired product, DMF. We demonstrate that control over metal nanoparticle size and composition, along with operating conditions, is crucial to achieving good performance and stability. Implications of this mechanism for other reactions and catalysts are discussed.
Selective oxidation of n-hexane by Cu (II) nanoclusters supported on nanocrystalline zirconia catalyst
Acharyya, Shankha Shubhra,Ghosh, Shilpi,Adak, Shubhadeep,Singh, Raghuvir,Saran, Sandeep,Bal, Rajaram
, p. 5816 - 5822 (2015)
Cu (II) nanoclusters supported on nanocrystalline zirconia catalyst (with size ～15 nm), was prepared by using cationic surfactant cetyltrimethylammonium in a hydrothermal synthesis method. The catalyst was characterized by XRD, XPS, TGA, SEM, TEM, FTIR and ICP-AES. The catalyst was found to be efficient in selective oxidation of n-hexane to 2-hexanol. An n-hexane conversion of 55%, with a 2-hexanol selectivity of 70% was achieved over this catalyst in liquid phase, without the use of any solvent. The catalyst can be reused several times without any significant activity loss.
Synthesis and Reactivity of Cobalt(I) and Iridium(I) Complexes Bearing a Pentadentate N-Homoallyl-Substituted Bis(NHC) Pincer Ligand
Tian, Yingying,Maulbetsch, Theo,Jordan, Ronja,T?rnroos, Karl W.,Kunz, Doris
, p. 1221 - 1229 (2020)
Two methods for the synthesis of the bis(imidazolin-2-ylidene)carbazolide cobalt(I) complex [Co(bimcaHomo)] (2) have been developed. The first route relies on the direct transmetalation of the in situ generated lithium complex [Li(bimcaHomo)] with CoCl(PPh3)3. The second route is a two-step synthesis that consists of the transmetalation of [Li(bimcaHomo)] with CoCl2 followed by reduction of the Co(II) complex to yield the desired Co(I) complex 2. The analogous iridium complex [Ir(bimcaHomo)] (4) was prepared by transmetalation of [Li(bimcaHomo)] or [K(bimcaHomo)] with [Ir(μ-Cl)(COD)]2. The catalytic activity of complexes 2 and 4 in the epoxide isomerization was tested in the absence and presence of H2. When [M(bimcaHomo)] (M = Ir (4), Rh (3)) was exposed to 1 bar of H2 at 80 °C, single crystals formed whose X-ray structure analyses revealed the hydrogenation of the N-homoallyl moieties and formation of the dimeric hydrido complexes [Ir(bimcan-Bu)(H)2]2 (7) and [Rh(bimcan-Bu)(H)2]2 (8).
Experimental and theoretical study of gold(III)-catalyzed hydration of alkynes
Cordon, Jesus,Jimenez-Oses, Gonzalo,Lopez-De-Luzuriaga, Jose M.,Monge, Miguel,Olmos, M. Elena,Pascual, David
, p. 3823 - 3830 (2014)
The properties of different Au(III) halo dithiocarbamate complexes of structure [AuX2(S2CN(R)2)] as suitable catalysts for the hydration reaction of phenylacetylene have been tested. Moderate catalytic activity was found for X = Cl, Br, while those compounds in which X = I, C6F5 are inert. A working mechanism involving the initial dissociation of a labile ligand (Cl or Br) followed by coordination and activation of the alkyne, solvent-assisted attack of water, and enol tautomerization has been proposed through computational studies.
Wacker-type oxidation in vapor phase using a palladium-copper chloride catalyst in a liquid polymer medium supported on silica gel
Okamoto, Masaki,Taniguchi, Yuichi
, p. 195 - 200 (2009)
Pd(II) chloride and Cu(II) chloride in various liquid polymer media supported on silica gel were prepared and used in a catalyst system for vapor-phase synthesis of acetaldehyde by Wacker-type oxidation of ethylene. This catalyst system supported on silica gel prepared by impregnation was quickly deactivated, while use of polyethylene glycol (PEG) as a liquid polymer medium supported on silica gel showed stable catalytic activity. PEG inhibited the formation of Pd metal particles, which deactivate the catalyst system. Addition of alkali metal salts, especially LiCl, to the PdCl2-CuCl2 catalyst system with PEG enhanced catalytic activity for 22 h, even when the Pd content was high, leading to high activity but poor stability. LiCl also inhibited the formation of metal particles.
High-throughput measurement of the enantiomeric excess of chiral alcohols by using two enzymes
Li, Zhi,Buetikofer, Lukas,Witholt, Bernard
, p. 1698 - 1702 (2004)
Rapid ee determination: Enantioselective alcohol dehydrogenases A and B were used to oxidize chiral alcohols in a sensitive, accurate, high-throughput method (see scheme). The reaction rates were determined by monitoring the formation of NAD(P)H by UV spectroscopy. The ee value was calculated from the reaction rates and the kinetic constants of the enzymes.
