Kinetics of oxidation of methane to formaldehyde on Na<Subscript>4</Subscript>[PFeMo<Subscript>11</Subscript>O<Subscript>40</Subscript>]/SiO<Subscript>2</Subscript>

The kinetics of oxidation of CH₄ to formaldehyde on the catalytic system Na₄[PFeMo₁₁O₄₀]/SiO₂ were studied, and a significant role of the redox potential of the CH₄-O₂ system with respect to the catalyst was shown. The density of centers participating in the reaction was determined, and dissociative competitive adsorption of methane and oxygen was established. The equation was deduced in the framework of the Langmuir-Hinshelwood theory taking into account the side conversion of formaldehyde. Possible participation of lattice oxygen in the reaction was suggested.     

Synthesis and Crystal Structure of the Octametallic Ferrocene Containing Molybdenum(V) Cluster Mo4(μ3-O)4(μ2-O2P(CH2)2Fc)4O4 and Crystal Structure of 1,1′-Bis(Chloromethyl)Ferrocene

The reaction of MoO₂(acac)₂ with 1,1??-[phosphinicobis(methylene)]-ferrocene in ethanol at 120?°C and in the presence of triethylamine results in the octametallic cluster Mo₄(??₃-O)₄(??₂-O₂P(CH₂)₂Fc)₄O₄. If the reaction is carried out in the absence of triethylamine a mixture of products are obtained of which the identity of the compound produced was hypothesized but not definitively established. Mo₄(??₃-O)₄(??₂-O₂P(CH₂)₂Fc)₄O₄ is characterized by IR and ³¹P-NMR spectroscopy along with the single crystal X-ray determination of its structure. The crystal structure of 1,1??-bis(chloromethyl)ferrocene is also detailed.     

Features of the electronic structure of ruthenium tetracarboxylates with axially coordinated nitric oxide (II)

The electronic structure of Ru₂(μ-O₂CR)₄, Ru₂(μ-O₂CR)₄(L)₂ and Ru₂(μ-O₂CR)₄(NO)₂ (R = H, CH₃, CF₃; L = H₂O, THF) ruthenium tetracarboxylates is analyzed on the basis of calculations by the density functional method with full geometry optimization. It is concluded that the axial coordination of nitric oxide (II) to Ru₂(μ-O₂CR)₄ is accompanied by destruction of the metal-metal π-bond with d _πAO Ru reorientation on bonding with NO molecules.     

Synthesen nitro-substituierter cis-bis(phenyl)platin(II)-verbindungen

Syntheses of the compounds [Pt(η⁴-COD)(4-XC₆H₄)(4-O₂NC₆H₄)] (X = (CH₃₂N, CH₃O, CH₃, NO₂; COD = 1,5-cyclooctadiene) and cis-{Pt[P(C₆H₅₃]₂- (4-O₂NC₆H₄(4-XC₆H₄)} (X = CF₃, NO₂) are reported. Experiments to synthesize cis-{Pt[P(C₆H₅)₃]₂(4-O₂NC₆H₄(4-XC₆H₄} (X = (CH₃₂N, CH₃O, CH₃) with an electron donor in one and an electron acceptor in the second platinum-bonded phenyl ring resulted in the spontaneous reductive elimination of 4-O₂NC₆H₄C₆-H₄X-(4). This observation supports the hypothesis of a donor-acceptor interaction in the transition state of the reductive biphenyl elimination.     

Lignin-type, α,β-unsaturated aldehydes of lignin-type in organic solvents

A 1:1 reaction of [HO(CH₂)₃]₃P with 4-hydroxy-3-methoxy-cinnamaldehyde (coniferaldehyde) or 3,5-dimethoxy-4-hydroxycinnamaldehyde (sinapaldehyde) in acetone at room temperature affords phosphonium zwitterions of the type R₃P⁺CH(4-O^?-Ar)CH₂CHO; other phosphines [R = Et, n-Bu, (CH₂)₂CN, and p-Tol] do not react under the same conditions. In alcohols R??OH(D) [R?? = CD₃, Et, (CD₃)₂CD, s-Bu, HOCH₂CH₂], the above phosphines (except the cyano-derivative) and those where R = i-Pr, Cy, Me₂Ph, MePh₂ do react within an equilibrium established between the reactants and the zwitterion-hemiacetal products R₃P⁺CH(4-O^?-Ar)CH₂CH(OH)(OR??) that are formed as a mixture of two diastereomers. The nature of the phosphine and the alcohol affects the equilibrium and the diastereomeric ratio.     

Migration of hydrogen from metal to alkene promoted by dioxygen addition. Oxygen atom transfer from a cis-(alkyl)(η2-dioxygen) complex of rhodium to organic and inorganic substrates

The novel cis-(σ-alkyl)(η²-O₂) complexes of rhodium [(THF)(EtOH)Naμ-EtOH₂μ-(CO₂R)CH₂CH(CO₂R)Rh(η²-O₂)(triphos)₂Na(EtOH)(THF)][BPh₄]₂·2EtOH (R = Me,3; Et,4) have been synthesized by reaction of dioxygen with the hydrides (triphos)(RhH(η²-alkene) followed by NaBPh₄ addition (alkene = dimethyl fumarate,1; diethyl fumarate,2) (triphos = MeC(CH₂PPh₂)₃). The structure of4 has been determined by X-ray diffraction. Oxygen atom transfer reactions from the η²-O₂ complexes to various inorganic and organic substrates have been studied.     

Binuclear ruthenium complexes of fluorous phosphine ligands: Synthesis, properties, and biphasic catalytic activity. Crystal structure of [Ru(μ-O2CMe)(CO)2P(CH2CH2(CF2)5CF3)3]2

The fluorocarbon soluble, binuclear ruthenium(I) complexes [Ru(μ-O₂CMe)(CO)₂L^F]₂, where L^F is the perfluoroalkyl substituted tertiary phosphine, P(C₆H₄-4-CH₂CH₂(CF₂)₇CF₃)₃, or P(CH₂CH₂(CF₂)₅CF₃)₃, were synthesized and partition coefficients for the complexes in fluorocarbon/hydrocarbon biphases were determined. Catalytic hydrogenation of acetophenone to 1-phenylethanol in benzotrifluoride at 105 °C occured in the presence of either [Ru(μ-O₂CMe)(CO)₂P(C₆H₄-4-CH₂CH₂(CF₂)₇CF₃)₃]₂ (1) or [Ru(μ-O₂CMe)(CO)₂P(CH₂CH₂(CF₂)₅CF₃)₃]₂ (2). The X-ray crystal structure of [Ru(μ-O₂CMe)(CO)₂P(CH₂CH₂(CF₂)₅CF₃)₃]₂ was determined. The compound exhibited discrete regions of fluorous and non-fluorous packing.     

Reaction of Organyltrifluorosilanes with Dimethylsulfoxide and Domethylformamide and Its Spectroscopic Investigation

Reaction of organyltrifluorosilanes RSiF₃ (R = C₆H₅, 3-O₂NC₆H₄, and C₆H₅CH₂) with DMSO and DMF (B) results in formation of the complexes 2B·SiF₄ and R₂SiF₂. Besides, biphenyl, benzene, methyl(fluoromethyl)sulfoxide, and S,S'-dimethyldisulfide-S,S'-dioxide CH₃S(O)S(O)CH₃ were either isolated or identified by chromatomass-spectrometry. Speculative mechanism of the reaction proceeding is discussed. IR spectra of the reaction mixtures and those of 2B·SiF₄ adduct were studied in details; they indicate octahedron structure of the complex with cis arrangement of B ligands.     

Syntheses, 95Mo NMR Spectroscopy and Structures of Distorted Cubic Mo4(��3-O)4(��2-O2P(CH2C6H5)2)4O4 and the Open Mixed-Valent Cluster, Mo4(��3-O)2(��2-O2P(CH2C6H5)2)6O6

The reaction of MoO₂(acac)₂ and dibenzylphosphinic acid in ethanol leads to a red distorted cubic tetrameric cluster, Mo₄(??³-O)₄(??²-O₂P(CH₂C₆H₅)₂)₄O₄, and a pink open mixed-valent cluster, Mo₄(??³-O)₂(??²-O₂P(CH₂C₆H₅)₂)₆O₆, when the reduction is carried out at 120 and 75 °C, respectively. ⁹⁵Mo NMR spectroscopy revealed a singlet for Mo₄(??³-O)₄(??²-O₂P(CH₂C₆H₅)₂)₄O₄ (1) at 584.9 ppm (????_1/2 = 4500 Hz) and two resonances for Mo₄(??³-O)₂(??²-O₂P(CH₂C₆H₅)₂)₆O₆ (2) at 238.8 ppm (????_1/2 = 1250 Hz) and 6.4 ppm (????_1/2 = 5999 Hz), which were assigned to the Mo(V) and Mo(VI) sites, respectively. DFT geometries and ⁹⁵Mo DFT-GIAO chemical shifts for Mo₄(??³-O)₄(??²-O₂P(CH₃)₂)₄O₄ (3) and Mo₄(??³-O)₂(??²-O₂P(CH₃)₂)₆O₆ (4) are consistent with X-ray crystallography and ⁹⁵Mo NMR of 1 and 2. The open complex, Mo₄(??³-O)₂(??²-O₂P(CH₂C₆H₅)₂)₆O₆·2(CH₂Cl₂), exhibits a central Mo(V)?CMo(V) single bond at 2.6217(5) Å with each Mo(V) atom bonded to one oxo (trans-disposed) terminal ligand.     

Binuclear ruthenium complexes of fluorous phosphine ligands: Synthesis, properties, and biphasic catalytic activity. Crystal structure of [Ru(μ-O2CMe)(CO)2P(CH2CH2(CF2)5CF3)3]2

The fluorocarbon soluble, binuclear ruthenium(I) complexes [Ru(μ-O₂CMe)(CO)₂L^F]₂, where L^F is the perfluoroalkyl substituted tertiary phosphine, P(C₆H₄-4-CH₂CH₂(CF₂)₇CF₃)₃, or P(CH₂CH₂(CF₂)₅CF₃)₃, were synthesized and partition coefficients for the complexes in fluorocarbon/hydrocarbon biphases were determined. Catalytic hydrogenation of acetophenone to 1-phenylethanol in benzotrifluoride at 105 °C occured in the presence of either [Ru(μ-O₂CMe)(CO)₂P(C₆H₄-4-CH₂CH₂(CF₂)₇CF₃)₃]₂ (1) or [Ru(μ-O₂CMe)(CO)₂P(CH₂CH₂(CF₂)₅CF₃)₃]₂ (2). The X-ray crystal structure of [Ru(μ-O₂CMe)(CO)₂P(CH₂CH₂(CF₂)₅CF₃)₃]₂ was determined. The compound exhibited discrete regions of fluorous and non-fluorous packing.     

On the mechanism of the ion-molecule reaction CH3+ + CH4 = C2H5+ + H2

Experimental evidence supporting the “direct” reaction model and the “intermediate complex” model for the reaction CH₃⁺(CH₄, H₂)C₂H₅⁺ are analysed. It is shown that the evidence for the former can equally well be interpreted in terms of a proposed model of persistent complex formation and decay. The plausibility of a “direct” mechanism is discussed and is found to be poor.     

Stoichiometric Aldehyde Deformylation Mediated by Nucleophilic Peroxo-diiron(III) Complex as a Functional Model of Aldehyde Deformylating Oxygenase

The reactivity of the previously reported peroxo adduct [Fe^III₂(μ-O₂)(MeBzim-Py)₄(CH₃CN)₂]⁴⁺ ( 1 ) (MeBzim-Py=2-(2′-pyridyl)-N-methylbenzimidazole) towards aldehyde substrates including phenylacetaldehyde (PAA), hydrocinnamaldehyde (HCA), propionaldehyde (PA), 2-phenylpropionaldehyde (PPA), cyclohexanecarboxaldehyde (CCA), and para-substituted benzaldehydes (benzoyl chlorides) has been investigated. Complex 1 proved to be a nucleophilic oxidant in aldehyde deformylation reaction. These models, including detailed kinetic and mechanistic studies, may serve as the first biomimics of aldehyde deformylating oxygenase (ADO) enzymes.     

基于密度泛函理论对等离子体中H/CO2相互作用的第一性原理研究

深入理解辐照条件下氢同位素与CO₂反应的微观机制,可为聚变堆氘氚燃料循环工艺的优化设计提供数据支撑。基于此,采用第一性原理计算研究了等离子体放电条件下H₂和CO₂的微观反应机制,研究了不同温度和氢同位素效应对反应过程的影响。通过内禀反应坐标（IRC）算法结合反应过渡态获得4条初始反应路径,并对比研究了生成产物CH₄及CH₃OH的2条路径在热力学上的容易程度,以及不同氢同位素对各个反应的影响。研究发现,氚的自发衰变或等离子体中的高能电子都会诱导氢同位素与CO₂发生反应,形成CO、H₂O、CH₄及CH₃OH等产物;在高能电子诱导CO₂的离解后,由4条初始反应路径组成的复杂反应可以自持发生,且该复杂反应中存在2种倾向;升高反应温度对CO₂转化为有机物（CH₄和CH₃OH）具有一定的促进作用。     

Synthesis, reactions and X-ray crystal structures of metallacrown ethers with unsymmetrical bis(phosphinite) and bis(phosphite) ligands derived from 2-hydroxy-2′-(1,4-bisoxo-6-hexanol)-1,1′-biphenyl

Chlorodiphenylphosphine and 2,2′-biphenylylenephosphorochloridite react with 2-hydroxy-2′-(1,4-bisoxo-6-hexanol)-1,1′-biphenyl to yield the new α,ω-bis(phosphorus-donor)-polyether ligands, 2-Ph₂PO(CH₂CH₂O)₂–C₁₂H₈-2′-OPPh₂ (1) and 2-(2,2′-O₂C₁₂H₈)P(CH₂CH₂O)₂–C₁₂H₈-2′-P(2,2′-O₂C₁₂H₈) (2). These ligands react with Mo(CO)₄(nbd) to form the monomeric metallacrown ethers, cis-Mo(CO)₄{2-Ph₂PO(CH₂CH₂O)₂–C₁₂H₈-2′-OPPh₂} (cis-3) and cis-Mo(CO)₄{2-(2,2′-O₂C₁₂H₈)P(CH₂CH₂O)₂–C₁₂H₈-2′-P(2,2′-O₂C₁₂H₈)} (cis-4), in good yields. The X-ray crystal structures of cis-3 and cis-4 are significantly different, especially in the conformation of the metal center and the adjacent ethylene group. The very different ¹³C-NMR coordination chemical shifts of this ethylene group in cis-3 and cis-4 suggest that the solution conformations of these metallacrown ethers are also quite different. Both metallacrown ethers undergo cis–trans isomerization in the presence of HgCl₂. Although the cis–trans equilibrium constants for the isomerization reactions are nearly identical, the isomerization of cis-3 is more rapid. Phenyl lithium reacts with cis-3 to form the corresponding benzoyl complexes but does not react with either trans-3 or cis-4. Both the slower rate of cis–trans isomerization of cis-4 and its lack of reaction with PhLi are consistent with weaker interactions between the hard metal cations and the carbonyl oxygens in both trans-3 and cis-4.     

Interaction of carboxyl functionalized catechols with palladium(II) and platinum(II) halide complexes

Summary A series of stable carboxyl substituted catecholato metal complexes of the type M(1,2-O₂C₆H₃R-4)(PPh₃)₂: M = Pd^II an Pt^II: R = CO₂H, CH₂CO₂H, C₂H₄CO₂H; have been prepared in high yield from reaction of the metal halide complex with catechols in the presence of a base. The compounds have been characterized on the basis of their elemental analyses. i.r. and n.m.r. spectra. The possibility of a metal carboxylato chelation had been considered and discussed on the light of the i.r. and n.m.r. spectra.     

A STUDY OF THE PHOTOPHYSICAL AND PHOTOCHEMICAL PROPERTIES OF THE S8 MOLECULE Photochemical Reactions in the S8 + Liquid Methanol System with and without Sensitizers: Benzene,Naphthalene and Pyrene. II

Abstract

The photochemical reactions occurring in the system S₈ + CH₃OH in the liquid phase were investigated, in the presence of, and without sensitizers. The experimental conditions were identical with those employed in studying the quenching of fluorescence.¹

The decay of S₈ is more rapid in the presence of sensitizers (the quantum yield and the degree of conversion are higher). In the system studied irradiation by UV light (λ 254 nm) causes the formation of (CH₃)₂S and of trace amounts of CH₄ and C₂H₆. The process of S₈ decay is of a mixed kinetic character—a pseudo 1st order process predominating, with a contribution from a 2nd order reaction. A possible reaction scheme, associated with excitation energy transfer from sensitizers to S₈ is discussed.     

Reactions of CH3O2 radicals on solid surface

The reaction probability of CH₃O₂ radicals with NO₂, CH₄, C₃H₆, and CH₃CHO on the solid surface of KCl in flow at low pressure and temperature range of 297–353 K has been studied. The chosen conditions allowed excluding homogeneous interaction of radicals. The heterogeneous radical decay of peracetic acid served as a source of CH₃O₂ radicals. On the basis of ESR measurements of CH₃O₂ radicals with the above‐mentioned compounds, a heterogeneous reaction mechanism has been identified. The reactivity of NO₂ was greatest for the compounds studied. The effective activation energy was evaluated to be 10.4 ± 0.8 kJ/mol for the reaction of RO₂ radicals with NO₂ and ?21.3 ± 2.8 kJ/mol for methane. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 591–595, 2004     

Electride-Sponsored Radical-Controlled CO2 Reduction to Organic Acids: A Computational Design

Converting CO₂ into high-value chemicals has been regarded as an important solution for a sustainable low-carbon economy. In this work, we have theoretically designed an innovative strategy for the absorption and activation of CO₂ by the electride N3Li, that is, 1,3,5(2,6)-tripyridinacyclohexaphane (N3) intercalated by lithium. DFT computations showed that the interaction of CO₂ with N3Li leads to the catalytic complex N3Li(η²-O₂C), which can initiate the radical-controlled reduction of another CO₂ to form organic acids through radical reactions in the gas phase. The CO₂ reduction consists of four steps: (1) The formation of N3Li(η²-O₂C) through the combination of N3Li and CO₂, (2) hydrogen abstraction from RH (R=H, CH₃, and C₂H₅) by N3Li(η²-O₂C) to form the radical R^. and N3Li(η²-O₂C)H, (3) the combination of CO₂ and the radical R^. to form RCOO^., and (4) intermolecular hydrogen transfer from the intermediate N3Li(η²-O₂C)H to RCOO^.. In the whole reaction process, the CO₂ moiety in the complex N3Li(η²-O₂C) maintains a certain radical character at the carbon atom of CO₂ and plays a self-catalyzing role. This work represents the first example of electride-sponsored radical-controlled CO₂ reduction, and thus provides an alternative strategy for CO₂ conversion.     

Formaldehyde interaction with adsorbed oxygen on open-circuit platinum electrodes in aqueous sulfuric acid solutions

The open circuit potential transients and cathodic potentiodynamic pulses were measured upon formaldehyde (methylene glycol) interaction with pre-adsorbed oxygen (O_ads) on Pt/Pt and pc Pt electrodes in aqueous sulfuric acid solutions. The slowest interaction of CH₂(OH)₂ with O_ads was observed in the high coverage range of the electrode surface (θ_O ～ 0.2 0.8 to 1). The process rate in this range is determined by the direct reaction of O_ads with CH₂(OH)₂ molecules from the bulk solution. In the middle surface oxygen coverage range (θ_O 0.2 to 0.8), CH₂(OH)₂ interaction with O_ads takes place by the mechanism of “conjugated reactions”. The kinetic parameters of reactions for CH₂(OH)₂, HCOOH, and CH₃ OH were compared. The rate of CH₂(OH)₂-O_ads interaction on Pt electrodes in the high oxygen coverage range was found higher by an order of magnitude than that of HCOOH and by two orders of magnitude than in the case of CH₃OH.