Homogeneous Metal Complex Catalysts Research Articles

Catalysts for Liquid-Phase Oxidation of Organic Compounds by Hydrogen Peroxide: Homogeneous and Phase-Transfer Systems

The review presents a comparative analysis of promising homogeneous metal complex catalysts and presents the results of studies on the synthesis and determination of the structural characteristics of effective catalysts for the oxidation of organic compounds with hydrogen peroxide – Q3{PO4[WO(O2)2]4} (Q is a quaternary ammonium cation) – using methods EXAFS, SAXS, NMR, Raman and IR spectroscopy. The possibilities of using bifunctional homogeneous peroxopolyoxo complexes of metals in combination with organic cations having quaternized nitrogen under the conditions of interfacial catalysis are considered, using examples of reactions of oxidation of various classes of organic compounds with hydrogen peroxide to obtain popular products – aliphatic and aromatic epoxides, mono- and dicarboxylic acids, as well as biologically active compounds for medical and agro-industrial purposes.

Preparation of aurum chloride complex and its use for industrial acetylene hydration catalyst process

The use of a modern homogeneous metal complex catalyst for the hydration of acetylenes is being investigated. The process is relevant both for the industry of basic organic synthesis and for the perfume industry. The analysis of existing processes used in industry for the production of acetaldehyde was carried out. Significant shortcomings of existing processes are revealed: low environmental friendliness and high energy consumption. To solve this problem, the reaction of hydration of an acetylene compound was studied using a modern homogeneous catalyst based on gold, which is not toxic. The study was conducted by selecting aliquots during the reaction. Using the 1H NMR spectroscopy method, the conversion values of phenylacetylene were calculated for the time values corresponding to the moments of aliquot sampling. The reaction order with respect to phenylacetylene was calculated and the reaction constant under the reaction conditions was calculated. When reacting in the presence of the proposed catalyst, a conversion of phenylacetylene of 86.96 % is achieved in 3 hours. The data obtained provide grounds for carrying out the process of catalytic hydration of acetylenes, namely phenylacetylene, with the production of acetophenone, which is important for use in the perfume industry. The data obtained can be applied to the process of hydration of acetylene with the formation of acetaldehyde, which is widely used in the industry of basic organic synthesis. For the process of catalytic hydration of acetylene compounds, a hardware design is proposed, a gas-liquid reactor with a changing hydrodynamic situation, which, together with the product separation column, is combined into a single installation. Using an optimized method, a catalyst based on gold chloride was synthesized from a gold alloy.

Homogeneous Metal-Complex Catalyst Systems in the Partial Oxidation of Propane with Oxygen

Homogeneous Metal-Complex Catalyst Systems in the Partial Oxidation of Propane with Oxygen

“Golden Age” of Homogeneous Catalysis Chemistry of Alkynes: Dimerization and Oligomerization of Alkynes

History of the development and use of homogeneous metal complex catalysts in the chemistry of acetylene and its derivatives is considered. Achievements of the catalytic chemistry of alkynes in the creation of affective catalytic systems (based on Groups 3—11 and 13 of the Periodic Table) for alkyne dimerization, capable of producing desired dimeric isomers possessing high chemo-, stereo- and regioselectivity are analyzed. The nature of elementary stages in four mechanisms of dimerization and the relations of the nature of organometallic intermediates to the nature of catalyst (metal and ligand), substrate, and type of mechanism, and, hence, to the selectivity of dimerization process are discussed.

Encapsulation of Homogeneous Catalysts in Mesoporous Materials Using Diffusion-Limited Atomic Layer Deposition.

The heterogenization of homogeneous metal complex catalysts has attracted great attention. The encapsulation of metal complexes into nanochannels of mesoporous materials is achieved by coating metal oxides at/near the pore entrance by diffusion-limited atomic layer deposition (ALD) to produce a hollow plug. The pore size of the hollow plug is precisely controlled on the sub-nanometer scale by the number of ALD cycles to fit various metal complexes with different molecular sizes. Typically, Co or Ti complexes are successfully encapsulated into the nanochannels of SBA-15, SBA-16, and MCM-41. The encapsulated Co and Ti catalysts show excellent catalytic activity and reusability in the hydrolytic kinetic resolution of epoxides and asymmetric cyanosilylation of carbonyl compounds, respectively. This ALD-assisted encapsulation method can be extended to the encapsulation of other homogeneous catalysts into different mesoporous materials for various heterogeneous reactions.

Encapsulation of Homogeneous Catalysts in Mesoporous Materials Using Diffusion‐Limited Atomic Layer Deposition

AbstractThe heterogenization of homogeneous metal complex catalysts has attracted great attention. The encapsulation of metal complexes into nanochannels of mesoporous materials is achieved by coating metal oxides at/near the pore entrance by diffusion‐limited atomic layer deposition (ALD) to produce a hollow plug. The pore size of the hollow plug is precisely controlled on the sub‐nanometer scale by the number of ALD cycles to fit various metal complexes with different molecular sizes. Typically, Co or Ti complexes are successfully encapsulated into the nanochannels of SBA‐15, SBA‐16, and MCM‐41. The encapsulated Co and Ti catalysts show excellent catalytic activity and reusability in the hydrolytic kinetic resolution of epoxides and asymmetric cyanosilylation of carbonyl compounds, respectively. This ALD‐assisted encapsulation method can be extended to the encapsulation of other homogeneous catalysts into different mesoporous materials for various heterogeneous reactions.

ChemInform Abstract: Chiral Metal Nanoparticle Systems as Heterogeneous Catalysts Beyond Homogeneous Metal Complex Catalysts for Asymmetric Addition of Arylboronic Acids to α,β‐Unsaturated Carbonyl Compounds.

AbstractA secondary amide‐substituted, chiral diene‐modified Rh/Ag nanoparticles system is developed as novel heterogeneous system and employed for asymmetric C—C bond‐forming reactions.

Chiral Metal Nanoparticle Systems as Heterogeneous Catalysts beyond Homogeneous Metal Complex Catalysts for Asymmetric Addition of Arylboronic Acids to α,β-Unsaturated Carbonyl Compounds.

We describe the use of chiral metal nanoparticle systems, as novel heterogeneous chiral catalysts for the asymmetric 1,4-addition of arylboronic acids to α,β-unsaturated carbonyl compounds, as representative C-C bond-forming reactions. The reactions proceeded smoothly to afford the corresponding β-arylated products in high to excellent yields and outstanding enantioselectivities with wide substrate scope. Remarkably, the nanoparticle catalysts showed performance in terms of yield, enantioselectivity, and catalytic turnover that was superior to that of the corresponding homogeneous metal complexes. The catalyst can be successfully recovered and reused in a gram-scale synthesis with low catalyst loading without significant loss of activity. The nature of the active species was investigated, and we found that characteristic features of the nanoparticle system were totally different from those of the metal complex system.

Hybrid photocatalytic H2 evolution systems containing xanthene dyes and inorganic nickel based catalysts

Abstract The application of nickel based earth abundant inorganic solids as catalysts in xanthene dye sensitized systems was evaluated for photocatalytic H2 production from water. The introduction of heterogeneous nanoparticles into molecular systems as catalysts is the conceptual begin to broaden the construction of photocatalytic H2 production systems. A series of Ni based inorganic nanoparticles, including Ni metal, NiO, NiS and NiSe, are capable of producing H2 from triethanolamine sacrificial aqueous solution when photosensitized by xanthene dyes. NiS catalysts synthesized from different methods were also evaluated for H2 production performance. The best H2 production result is obtained with the use of Erythrosin Y as the photosensitizer and NiS synthesized in ethylene glycol as the catalyst. This system is active even under photons with wavelengths longer than 520 nm with a H2 production of 2.5 mmol within 26 h of irradiation from a 300 W Xenon lamp. Meanwhile, it can generate over 4.2 mmol of H2 within 16 h of irradiation with a 440 nm long-pass cut-off filter. Within the visible light range we examined, the highest quantum efficiency is around 15% at 520 nm. The high activity of NiS could be contributed by its high electrochemical activity, metallic nature, unsaturated Ni environment and suitable Fermi energy level. These hybrid systems consist of earth abundant elements, and the catalyst is photostable and recyclable compared to homogeneous metal complex catalyst.

Catalytic oxidation of organic substrates with hydrogen peroxide in two-phase systems in the presence of peroxo-polyoxotungstates containing organic ligands

The prospects of using bifunctional homogeneous metal-complex catalysts based on peroxo-polyoxotungstates with organic ligands (tertiary phosphine oxides) were exemplified by oxidation of benzyl alcohol and cyclooctene with hydrogen peroxide in two-phase systems (organic phase — liquid phase).

Green Carbon—Carbon Bond‐Forming Reactions by Heterogeneous Metal Catalysts

AbstractFor Abstract see ChemInform Abstract in Full Text.

不均一系金属触媒を用いた自然共生型炭素‐炭素結合形成反応

The organic reactions mediated by solid surface come closest to an ideal simplified version of chemical processes. This article describes development of heterogeneous metal catalysts aiming at 'green' carbon-carbon bond-forming reactions, based on unique properties of inorganic crystals, i.e. hydroxyapatite, montmorillonite, and hydrotalcite.A coordinatively-unsaturated Ru species generated on the hydroxyapatite surface efficiently catalyzes Diels-Alder reaction as well as aldol reaction of nitriles with carbonyl compounds in water solvent as a Lewis acid. A robust Pd2+ species on a Ca-deficient hydroxyapatite is capable of promoting Heck and Suzuki coupling reactions.A Sc (H2O) 6 species within the expansible interlayer space of montmorillonite shows an outstanding catalysis for Michael reaction of 1, 3-dicarbonyls even under solventless conditions. Allylation of carbonyl compounds with allyltrimethylsilane proceeds smoothly using Mn+-montmorillonite catalysts to afford homoallylic alcohols. Self-organized hydrotalcite provides a unique base catalyst in aldol reaction of aldehydes in water.The above functionalized and recyclable solid catalysts offer 'green' protocols of carbon-carbon bond-forming reactions to replace conventional methods using stoichiometric reagents and homogeneous metal complex catalysts.

Synthesis of acetic acid from methanol alone by homogeneous metal complex catalyst. Part 4 . In-situ formation of catalyst species and halogen effect in the RuCl 3·3H 2O–SnX 2 (X=F, Cl, Br, I) composite system

Highly selective formation of methyl acetate has been found possible from methanol alone using the catalyst generated in situ from RuCl 3·3H 2O and SnCl 2 as well as SnX 2 (X=F, Br, I). The reaction did not occur in the absence of SnCl 2 added and the optimum [Sn]/[Ru] ratio appeared at about 16. The halogen effect showed the order of SnF 2>SnCl 2>SnBr 2>SnI 2, which indicates the importance of cationic character of Ru(II) center to facilitate its electrophilic interaction with β-hydrogen of Ru–OCH 3 intermediate in the rate-limiting dehydrogenation step.

Synthesis of acetic acid from methanol alone by homogeneous metal complex catalyst. Part II . Mechanistic study on methyl acetate formation from methanol alone by [( η5-C 5H 5)(PPh 3) 2RuX] (X=Cl, SnF 3) complex catalyst

Catalytic activity of [( η 5-C 5H 5) (PPh 3) 2RuX] (X=Cl ( 1), SnF 3 ( 2)) was investigated for the highly selective formation of methyl acetate with methanol used as the sole source. Complex 2 was found to be more catalytically active than the singlemetallic complex 1. For both complexes, the initial reaction rate was first order with respect to the catalyst concentration, and a saturation curve was obtained for dependence on the reactant concentration. Extra addition of Cl − ion considerably slowed the reaction with 1 taken as catalyst, and an almost linear relationship was obtained between the reciprocal of initial rate and the concentration of added Cl − ion. This fact indicates the presence of pre-equilibrium to form catalyst-reactant complex through the substitution of Cl − ligand. In the case of 2, extra addition of PPh 3 gave a similar effect on the rate, allowing the same type of kinetic analysis. The role of Sn(II) ligand is considered in line with the mechanism that satisfies the rate equations derived from these kinetic results.

ChemInform Abstract: Synthesis of Cyclobutane and Cyclopentane Compounds Using Homogeneous Metal Complex Catalysts

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Synthesis of cyclobutane and cyclopentane compounds using homogeneous metal complex catalysts

Synthesis of cyclobutane and cyclopentane compounds using homogeneous metal complex catalysts