Homogeneous Catalysis of C-H Bond Activation by a Novel Ruthenium(III)-Complex

A novel mixed-ligand [Ru^III(amp)(pic)(H₂O)] complex (1) (H₂amp = N-(hydroxyphenyl)salicyldimine; pic = picolinate) has been synthesized and characterized by physico-chemical methods. Complex 1has been found to be an effective catalyst in oxo-functionalization of C-H bond of organic substrates by using tert-butyl hydroperoxide (t-BuOOH) as a terminal oxidant. Formation of a high valent Ru(V)-oxo species as catalytic intermediate is proposed to be the source of oxygen atom in the oxidised product.     

Sol-Gel as Reaction Matrix for Bacterial Enzymatic Activity

Sol-gel process is a rapid growing field in material chemistry. The sol-gel matrices (SGM) are basically porous wet-gels or xerogels obtained by the hydrolysis and condensation-polymerisation of metal and semimetal alkoxides, mainly SiO₂ materials. The current study presents the uses of sol-gel glass matrix (SGM) that allow direct entrapment of biomolecules within and at surface, which can be utilized by microorganisms. This glass type is solid, transparent, porous and can be modulated to form a hydrophobic or hydrophilic surface. In view of all these beneficial characteristics of SGM, preliminary data is presented on biofilm formed on thin films of SGM doped with a fluorochrome (fluorescein diacetate). The esterase/lipase activity of E. coli CN ₁₃ and K. oxytoca spp. biofilm grown on top of SGM thin film, doped with fluorescein diacetate, was detected at the level of a single cell by epifluorescence microscopy. In view of these preliminary results, sol-gel glass has a considerable potential as a variable matrix for single bacteria and biofilm investigation.     

Olefin epoxidation catalyzed by [Ru(TDL)(tmeda)H2O] complexes (TDL = tridentate Schiff-base ligand; tmeda = tetramethylethylenediamine)

Mixed-chelate complexes of ruthenium have been synthesized using tridentate Schiff-base ligands (TDLs) derived from condensation of 2-aminophenol or 2-aminobenzoic acid with aldehydes (salicyldehyde, 2-pyridinecarboxaldehyde), and tmeda (tetramethylethylenediamine). [Ru^III(hpsd)(tmeda)(H₂O)]⁺ (1), [Ru^III(hppc)(tmeda)(H₂O)]²⁺ (2), [Ru^III(cpsd)(tmeda)(H₂O)]⁺ (3) and [Ru^III(cppc)(tmeda)(H₂O)]²⁺ (4) complexes (where hpsd²⁻ = N-(hydroxyphenyl)salicylaldiminato); hppc⁻ = N-(2-hydroxyphenylpyridine-2-carboxaldiminato); cpsd²⁻ = (N-(2-carboxyphenyl)salicylaldiminato); cppc⁻ = N-2-carboxyphenylpyridine-2-carboxaldiminato) were characterized by microanalysis, spectral (IR and UV–vis), conductance, magnetic moment and electrochemical studies. Complexes 1–4 catalyzed the epoxidation of cyclohexene, styrene, 4-chlorostyrene, 4-methylstyrene, 4-methoxystyrene, 4-nitrostyrene, cis- and trans-stilbenes effectively at ambient temperature using tert-butylhydroperoxide (t-BuOOH) as terminal oxidant. On the basis of Hammett correlation (log k_rel vs. σ⁺) and product analysis, a mechanism involving intermediacy of a [Ru–O–OBu^t] radicaloid species is proposed for the catalytic epoxidation process.     

Barrier Compression Enhances an Enzymatic Hydrogen‐Transfer Reaction

Putting the squeeze on : Hydrostatic pressure causes a shortening of the charge‐transfer bond in the binary complex of morphinone reductase and NADH₄ (see diagram). Molecular dynamics simulations suggest that pressure reduces the average reaction barrier width by restricting the conformational space available to the flavin mononucleotide and NADH within the active site. The apparent rate of catalysis increases with pressure.

     

P-Chiral monodentate diamidophosphites as ligands for Rh-catalyzed asymmetric reactions

A series of P-chiral monodentate diamidophosphite ligands of the 1,3-diaza-2-phosphabicyclo[3.3.0]octane family was tested in the Rh-catalyzed hydrogenation of dimethyl itaconate and addition of phenylboronic acid at the carbonyl group of trans-cinnamaldehyde. The enantioselectivities and conversions of these reactions are strongly dependent on the nature of the exo-cyclic substituent of the ligand. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2023–2025, October, 2007.     

Supported complexes of cupric chloride with DMF as catalysts in the reaction of CCl4 withn-decane

The complex of cupric chloride with DMF immobilized on the surface of silica gel exhibits high catalytic activity in the reaction of tetrachloromethane withn-decane. The fact that the reaction is inhibited by phenols and oxygen implies that it occurs by a radical mechanism. The immobilized catalyst that contains copper atoms connected through chlorine bridges and organic donor ligands is the most effective. Presented at the First Moscow Workshop on Highly Organized Catalytic Systems. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1835–1838, October, 1997.     

铂纳米颗粒的可见光化学制备及其对p-硝基苯酚催化还原反应

在可见光照射下,以乙二醇（EG）作为还原剂和稳定剂,在多壁碳纳米管（MWCNTs）上一步合成了铂纳米颗粒,成功制备Pt/MWCNTs复合材料,并通过p-硝基苯酚（p-NP）的催化还原反应研究了Pt/MWCNTs的催化性能。用傅里叶变换红外光谱（FT-IR）、X射线衍射（XRD）、透射电子显微镜（TEM）和X射线光电子能谱（XPS）对所制备材料的形貌和晶体结构进行了表征。实验结果显示,可见光照射促进了EG水溶液中[PtCl₄]^2-前驱体的水解。通过金属界面的电子效应,铂前驱体被还原成了均匀分散的平均直径2.1 nm的超小颗粒Pt（Pt ultra-small particles,Pt UPs）。所制备的Pt/MWCNTs能有效地催化p-NP还原为p-氨基苯酚（p-AP）,表现出较高的催化性能,其表观速率常数为0.25 min^-1。Pt/MWCNTs多次使用后没有显著的活性损失,显示出了良好的稳定性。上述实验结果证明,除了传统的紫外光照射等手段以外,可见光照射也同样是制备铂金属催化剂非常有效的方法。而且,催化剂的形貌控制也完全可以通过简单而非复杂的实验条件加以实现。     

Temperature Dependences of the Kinetic Isotope Effect and the Ratio of the Reaction Rates for Reaction of Cyclopentane and Cyclohexane with HOCl in Water

We have determined the activation parameters logA and E for the Arrhenius equations for the kinetic isotope effect (c-C₆H₁₂/c-C₆D₁₂) and the 5/6 effect (c-C₅H₁₀/c-C₆H₁₂) in reactions of the C—H bonds of cycloalkanes with HOCl in aqueous solutions in the interval 30-90 °C. The data obtained are consistent with a chlorination mechanism including a pre-activation step with formation of an HO^· ... Cl^· pair, linear abstraction of the H atom by the OH group and angular attack by the Cl atom "at a distance" on the carbon atom.     

Preparation of Calix[4]arene Alkylamine Derivatives by Mannich Reaction and use as Phase-Transfer Catalysts for Esterification Reaction

In this study, 5,11,17,23-tetrakis[(N-ethylpiperazine)methyl]-25,26,27,28-tetrahydroxycalix[4]arene (3) and 5,11,17,23-tetrakis[(4-carboethoxy-N-piperidino) methyl]-25,26,27,28-tetrahydroxycalix[4]arene (4) were synthesized in one step according to the Mannich reaction by the treatment of calix[4]arene with a secondary amine (N-ethylpiperazine, ethyl-4-piperidincarboxylate) and formaldehyde. The calix[4]arene derivatives (3, 4) were characterized by a combination of FTIR, ¹H NMR and elemental analyses. The synthesized compounds were used in an esterification reaction as the phase transfer catalyst. The catalytic efficiency of the calix[4]arenes 3 and 4 was evaluated by carrying out the ester-forming reaction of alkali metal carboxylates (sodium butyrate or sodium caprylate) with p-nitrobenzyl bromide. It was observed that the ester-forming reaction of alkali metal carboxylates with p-nitrobenzyl bromide, using calix[4]arene-based catalyst 3 as a phase-transfer catalyst in dichloromethan, provided the best yields.     

Asymmetric transfer hydrogenation of ketones catalyzed by rhodium and iridium complexes with chiral bidentate Schiff's bases

Rhodium and iridium complexes of Schiff's bases derived from (1R,2R)- and (1S,2S)-diaminocyclohexane catalyze asymmetric transfer hydrogenation of alkyl aryl ketones in PrⁱOH at room temperature to give chiral secondary alcohols (up to 65% ee).     

Change of topology of the chemical interaction stage as a tool for the stereoselectivity control of PTC reactions

The relationship between the rate-limiting step of PTC and the site of the chemical interaction stage has been established for the cyclotriphosphazenes phenolysis reaction in liquid-liquid systems. Transfer of the site of the phenolysis of mono(aryloxy)cyclo-triphosphazenes from the bulk of the organic phase to the interface results in a change in the ratio of the products of the reaction ofcis- andtrans- isomers of bis(aryloxy)cyclo-triphosphazenes.In memory of the 75th anniversary of Member of the Academy of Sciences of Ukrainian SSR L. M. Litvinenko.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2102–2107, November, 1995.     

Excess molar volumes of diethyl carbonate with hydrocarbons or tetrachloromethane at 25°C

The excess molar volumes V _m ^E at atmospheric pressure and at 25°C for binary mixtures of diethyl carbonate with n-heptane, n-decane, n-tetradecane, 2,2,4-trimethylpentane, cyclohexane, benzene, toluene, or tetrachloromethane have been obtained over the whole mole-fraction range from densities measured with a vibrating-tube densimeter. The V _m ^E are positive for all the systems investigated, except for the mixture with toluene which is negative. The results for V _m ^E together with data previously published on excess molar enthalpies H _m ^E and excess molar Gibbs energies G _m ^E , suggest interactions between carbonate and hydrocarbons which are stronger with aromatic than with aliphatic hydrocarbons.Thermodynamics of binary mixtures containing organic carbonates, Part 10.     

Ternary complexes of nickel(II) withAMP,ADP andATP as primary ligands and some biologically important polybasic oxygen acids as secondary ligands

Summary Potentiometric equilibrium measurements have been made at 25±0.1 °C (=0.1 mol dm^–3 KNO₃) for the interaction of adenosine-5-mono-, -di-, and-triphosphate (AMP,ADP, andATP) and Ni(II) with biologically important secondary ligand acids (malic, maleic, succinic, tartaric, citric and oxalic acids) in a 1:1:1 ratio and the formation of various 1:1:1 mixed ligand complex species inferred from the potentiometricpH titration curves. Initial estimates of the formation constants of the resulting species and the acid dissociation constants ofAMP,ADP,ATP and secondary ligand acid, have been refined with SUPERQUAD computer program. In some systems logK values are positive, i.e. the ternary complexes are found to be more stable than the corresponding binary complexes. H-bond formation seems to be most effective in deciding the stability of the ternary complexes formed in solution. Stabilities of mixed ligand complexes increases in the orderAMP<ADP<ATP. With respect to the secondary ligands, the formation constants of the mixed lignads complexes decrease in the order succinic>maleic>tartaric>malic>citric>oxalic acid.

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Ternäre Komplexe von Nickel(II) mitAMP,ADP undATP als Primärliganden und einigen biologisch wichtigen polyfunktionellen Carbonsäuren als Sekundärliganden

Zusammenfassung Es wurde die Wechselwirkung von Adenosin-5-mono-, -di- und -triphosphat (AMP,ADP undATP) und Ni(II) mit biologisch relevanten Säuren als Sekundärliganden (Äpfel-, Malein-, Bernstein-, Wein-, Zitronen- und Oxalsäure) im Verhältnis 1:1:1 mittels potentiometrischer Gleichgewichtsmessungen bei 25±0.1 °C und =0.1 mol dm^–3 KNO₃ untersucht. Aus den potentiometrischepH-Titrationen ergaben sich verschiedene 1:1:1-Komplexe mit gemischten Liganden. Zunächst abgeschätzte Komplexbildungskonstanten und Säuredissoziations-konstanten vonAMP,ADP,ATP mit den als Sekundärliganden eingesetzten Säuren wurden über das SUPERQUAD-Rechenprogramm verfeinert. In einigen Systemen sind die Werte von logK positiv, was bedeutet, daß die ternären Komplexe stabiler sind als die entsprechenden binären Komplexe. In einige ternären Komplexen scheinen die Wasserstoffbrücken zwischen den Liganden entscheidend zu sein. Die Stabilitäten der gemischten Liganden steigen in der ReiheAMP<ADP<ATP an. Bezüglich der Sekundärliganden ergibt sich die absteigende Stabilitätsreihung Bernsteinsäure>Maleinsäure>Weinsäure>Äpfelsäure>Zitronensäure>Oxalsäure.

     

Reaction of 1,2,3,4-tetrahydro-isoquinoline enamines with quinones

The reaction of p-benzoquinone with enamino amides derived from 2,2-dimethyl-1,2,3,4-tetrahydrobenzo[f]isoquinoline proceeds through a Michael addition. The reaction of this quinone with the base of drotaverine leads to a derivative of indolo[2,1-a]isoquinoline. Fusion of isoquinoline enamines by the action of 2,3-dichloro-1,4-naphthoquinone leads to pentacyclic benzo[g]naphtho-[2,3-b]indolyzine-8,13-dione. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1565–1570, October, 2006.     

铜N-杂环卡宾化合物的合成及其在有机合成中的应用

N-杂环卡宾铜化合物具有简便易得,价廉低毒,性质稳定,结构类型多样并易于修饰等诸多优点,在很多领域具有重要的应用价值,因此铜的N-杂环卡宾化学在过去十几年中得到了快速发展。本文结合我们的工作,总结铜N-杂环卡宾化合物的合成方法、结构特点、转移卡宾配体用于合成其它金属卡宾化合物以及催化应用。     

Oxidation with the “O2−H2O2−VO3 −−pyrazine-2-carboxylic acid” reagent

n-Heptane is readily oxidized in acetonitrile under the action of H₂O₂ with a “vanadate anion-pyrazine-2-carboxylic acid” system as the catalyst in air to form isomeric heptyl hydroperoxides (detected by GLC) along with isomeric heptanols and heptanones. Heptyl hydroperoxides slowly decompose at low temperature yielding the corresponding alcohols and ketones (aldehyde). The values of the parameter of the relative normalized reactivity of the H atoms at the carbon atoms in positions 1, 2, 3 and 4 depend on the reaction time and concentrations of the reagents. The value of the parameter of selectivity C(1)∶C(2)∶C(3)∶ C(4) varies in the range from 1.0∶2.8∶2.9∶1.8 to 1.0∶5.6∶5.9∶5.3 The low selectivity of the reaction shows that the key role is played by the attack of highly reactive radical particles on the C−H bond of the alkane molecule. For Part 5, see Ref. 1. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 780–785, April, 1997.     

Aerogel nanoscale magnesium oxides as a destructive sorbent for toxic chemical agents

An autoclave hypercritical drying procedure has been used to prepare precursors of MgO from Mg(OCH₃)₂. This material was prepared with a specific surface area of 1200 m² g ¹. The dehydrated materials consisted of much smaller crystallites than conventionally prepared MgO and were free of OCH₃ groups. The precursors and samples of magnesium oxide were taken for experimental evaluation of their reactivity with mustard. The largest percentage of the conversion mustard into non-toxic products after the elapse of the reaction was 77%.