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.
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.
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).
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.
Comparison of HMF hydrodeoxygenation over different metal catalysts in a continuous flow reactor
Luo, Jing,Arroyo-Ramírez, Lisandra,Wei, Jifeng,Yun, Hongseok,Murray, Christopher B.,Gorte, Raymond J.
, p. 86 - 93 (2015)
The three-phase hydrodeoxygenation (HDO) of 5-hydroxymethylfurfural (HMF) and hydrogenation of 2,5-dimethylfuran (DMF) were studied over six carbon-supported metal catalysts (Pt, Pd, Ir, Ru, Ni, and Co) using a tubular flow reactor with 1-propanol solvent, at 180 °C and 33 bar. By varying the space time in the reactor, the reaction of HMF is shown to be sequential, with HMF reacting first to furfuryl ethers and other partially hydrogenated products, which then form 2,5-dimethylfuran (DMF). Ring-opened products and 2,5-dimethyltetrahydrofuran (DMTHF) were produced only from reaction of DMF. Rate constants for the pseudo-first-order sequential reactions were obtained for each of the metals. The selectivities for the reaction of DMF varied with the metal catalyst, with Pd forming primarily DMTHF, Ir forming a mixture of DMTHF and open-ring products, and the other metals forming primarily open-ring products. Catalyst stabilities followed the order Pt ～ Ir > Pd > Ni > Co > Ru. Since the stability order correlated with carbon balances in the product (>93% for Pt; 75% for Ru), deactivation appears to be caused by deposition of humins on the catalyst.
Synthesis of TS-1 zeolites from a polymer containing titanium and silicon
Xing, Jiacheng,Yuan, Danhua,Liu, Hanbang,Tong, Yansi,Xu, Yunpeng,Liu, Zhongmin
, p. 6205 - 6213 (2021/03/22)
The synthesis of TS-1 zeolites is regarded as a milestone in zeolite history, and it has led to the revolution of the green oxidation system of using H2O2as an oxidant, leaving only water as the byproduct. However, because of the highly hydrolyzable titanium source, the preparation of TS-1 requires complex synthesis conditions. Moreover, the difference in the hydrolysis rate between the silicon source and titanium source tends to increase the difficulty of titanium insertion into the framework, and it is easy to generate extra-framework Ti species during the synthesis. Here, a high-quality TS-1 zeolite with a large external surface area and free of extra-framework Ti species has been successfully synthesized by using a kind of novel polymer containing titanium and silicon. Due to the high hydrolysis resistance of the polymer reagent, a good matching of the hydrolysis rate between the silicon source and the titanium source is realized during crystallization, which facilitates the incorporation of titanium into the framework. Furthermore, the TS-1 zeolite exhibited excellent catalytic performance inn-hexane oxidation with hydrogen peroxide as the oxidant. This method of synthesizing zeolites from polymers is expected to be widely applied for the synthesis of other titanium-containing zeotype materials.
Boosting homogeneous chemoselective hydrogenation of olefins mediated by a bis(silylenyl)terphenyl-nickel(0) pre-catalyst
Lücke, Marcel-Philip,Yao, Shenglai,Driess, Matthias
, p. 2909 - 2915 (2021/03/14)
The isolable chelating bis(N-heterocyclic silylenyl)-substituted terphenyl ligand [SiII(Terp)SiII] as well as its bis(phosphine) analogue [PIII(Terp)PIII] have been synthesised and fully characterised. Their reaction with Ni(cod)2(cod = cycloocta-1,5-diene) affords the corresponding 16 VE nickel(0) complexes with an intramolecularη2-arene coordination of Ni, [E(Terp)E]Ni(η2-arene) (E = PIII, SiII; arene = phenylene spacer). Due to a strong cooperativity of the Si and Ni sites in H2activation and H atom transfer, [SiII(Terp)SiII]Ni(η2-arene) mediates very effectively and chemoselectively the homogeneously catalysed hydrogenation of olefins bearing functional groups at 1 bar H2pressure and room temperature; in contrast, the bis(phosphine) analogous complex shows only poor activity. Catalytic and stoichiometric experiments revealed the important role of the η2-coordination of the Ni(0) site by the intramolecular phenylene with respect to the hydrogenation activity of [SiII(Terp)SiII]Ni(η2-arene). The mechanism has been established by kinetic measurements, including kinetic isotope effect (KIE) and Hammet-plot correlation. With this system, the currently highest performance of a homogeneous nickel-based hydrogenation catalyst of olefins (TON = 9800, TOF = 6800 h?1) could be realised.
