Search

The experimental and density functional theory about the reaction of acetonitrile with a zerovalent nickel bis(dialkylphosphino)ethane fragment showed the C-CN bond activation to be favorable exclusively over C-H bond activation due to the strong thermodynamic driving force and slightly lower kinetic barrier.

Gated redox reactions involving the [[Cu[(dmp).sub.2](solvent)].sup.2+]/[[Cu[(dmp).sub.2]].sup.2+] couple (dmp=2,9,dimethyl-1,10-phenanthroline) in acetonitrile were investigated at elevated pressures. The results led to conclusion that the reverse cross-reaction of the gated reduction of the [[Cu[(dmp).sub.2](solvent)].sup.2+]/[[Cu[(dmp).sub.2]].sup.2+] couple proceeds through the product excited state while the direct self-exchange reaction proceeds through an ordinary process.

A study was conducted to determine whether the nucleophilic substitution of the p-nitrophenoxy group in [(CO).sub.5]Cr=C(O[C.sub.6][H.sub.4]-N[O.sub.2])Ph by a series of substituted phenoxide ions is concerted or stepwise. The tetrahedral intermediates formed in the reactions of [(CO).sub.5]Cr=C(O[C.sub.6][H.sub.4]-N[O.sub.2])Ph are much more stable than those in acyl transfers.

Cross-reaction rate constants and simple Markus cross-rate theories are used to analyze a wide range of reactivities to extract useful estimates of self-exchange electron transfer (ET) rate constants and their related activation energies. Results shows that although the principal factor affecting intermolecular ET rate constants is found to be [lambda], the electronic coupling effects are easily detectable and the dynamic range of the estimates is over a factor of 600.

Raman microscopy is a powerful method for providing spatially resolved, chemically selective information about the composition of materials. With confocal collection optics, the method is well suited to the analysis of small particles in contact with liquid solutions. In this work, the transport of an organic solvent component into small polystyrene particles is investigated. An inverted confocal Raman microscope is used to acquire spectra from individual 75-[micro]m polystyrene particles in contact with acetonitrile/water mixtures. Monitoring the Raman scattering from the C [equivalent to] N stretching mode of acetonitrile provides a measure of solvent uptake into the polymer material. The small collection volume defined by the confocal optics provides the micrometer spatial resolution needed to track solvent concentration at different locations within the particle with 30-s time resolution. The volume fraction of acetonitrile in water in the surrounding solution was varied in order to determine the concentration dependence of the diffusion kinetics. Modeling the transport of molecules into a particle was addressed by using finite element methods for the evaluation of the coupled space- and time-dependent differential equations that govern the molecular transport. The results indicate that the diffusion coefficient changes with the local solvent concentration in the polymer. At longer times, with the highest acetonitrile concentrations, an evolution of the solvent transport mechanism was observed, from a diffusive rate that depends on local concentration to a linear increase in concentration with time accompanied by measurable swelling of the particle volume.

The existence of a three-member electron-transfer series of single cubanes [(Tp)MoFe3S4](super z) (z = 3-, 2-, 1-) and a four-member series of double cubanes [(Tp)(sub 2)Mo2Fe6S8L4](super z) (z = 4-, 3-, 2-, 1-) with L = F(super -), Cl(super -), N3, PhS(super -) is showed by electrochemical methods, cluster synthesis and X-ray structure determinations. The synthesis and structure of [(Tp)(sub 2)Mo2Fe6S8F2.H2O](super 3-), a new topological analogue of the P(super N) cluster of nitrogenase, is presented (Tp = hydrotris(pyrazolyl)borate(1-)).

The novel pyridine-containing 14 membered macrocycle 3,11-dithia-7,17-diazabicyclo[11.3.1]heptadeca-1(17),13,-15-triene (L), which contains an N(sub 2)S(sub 2) donor set was synthesized and its protonation behavior was studied. The reactions between L and NiX(sub 2).6H(sub 2)O in ethanol or acetonitrile afforded the octahedral complexes and the square -planar complex [Ni(L)]-(X)(sub 2) were obtained by heating these octahedral complexes.

Both the reduction and oxidation kinetics of copper(super II/I)([118]aneS6) are studied in acetonitrile solution using a series of counter regents to determine the electron self-exchange rate constant (k11) for this complex. The resolved value of k11 = 3 X 10(super 3) M(super -1) s(super -1) is significantly smaller than values for related complexes involving homoleptic thioether ligands with all ethylene bridge.

Palladium-catalyzed procedures for the selective monoarylation of acetonitrile and primary nitriles are achieved using alpha-silyl nitriles in the presence of ZnF2. This procedure is compatible with a variety of functional groups, including cyano, keto, nitro and ester groups, on the aryl bromide.

Factors influencing the formation of the phosphazides or iminophosphoranes in the reaction of 1,3,5-cis-traizidocyclohexane with the electron rich tris(dialkylamino)phosphines P(NMe2)3 and N(CH2CH2NMe)3P in acetronitrile for 3 h is discussed. Findings show that the presence of electron-rich sterically crowded phosphorus in compounds of type 3b promotes protonation of nitrogen in the azido group, thus facilitating departure of [6bH](super +), benzene formation, and dinitrogen evolution.

The synthesis and structural characterization, determined by H1 and C13 NMR, for a new tetraester calix[4] arene derivative containing mixed pendant arm in its lower rim are reported. The medium effect on the binding process of tetraester calix[4]arene for metal cations are examined to establish the sites of interaction of the ligand with the metal cation, the composition of complex formed and the strength of ligand-cation interaction in different media.

The study reported that the charge transfer (CT) spectra of the pi-pi complexes formed by several aromatic amines and nitrogen heterocycle [acting as donors (Ds)] with acceptor A [A = tetracyanoethylene (TCNE), chloranil (CA)] was measured in acetonitrile. The density functional theory calculations were carried out in solvent to determine the probable geometric structure of the complexes that were responsible for the absorption bands.

An investigation was conducted on the room temperature thermodynamic and structural properties of acetonitrile clusters containing alkali ions (Na(super +), Cs(super +)) or halide ions ((I(super -)) via Monte Carlo simulations. The results indicate the importance of the relative strengths if ion-solvent and solvent-solvent interactions in the determination of interior vs. surface ionic cluster structure.

The interaction of lower rim calix940arene derivatives containing ester and ketone functional groups and bivalent cations has been investigated in various solvents. The presence of actonitrile leads to ligand's preorganization and these ligands discriminate between the various bivalent cations to the extent that a selectivity peak is found in terms of Gibbs energies when complexation data are plotted against cation solvation.

Hybride transfer from 10-methyl-9, 10-dihydroacridine (AcrH(sub 2)) to 3,6-diphenyl-1,2,4,5-tetrazine (Ph(sub 2)Tz), which contains a N=N double bond, occurs efficiently in the presence of Sc(OTf)(sub 3) (OTf = OSO(sub 2)CF(sub 3)) in deaerated acetonitrile (MeCN) at 298 K, whereas no reaction occurs in the absence of Sc(super 3+). The observed second-order rate constant (k(sub obs)) increases with increasing Sc(super 3+) concentration to approach a limited value.

The complex formation of uranyl UO(sub 2)(super 2+) with chloride ions in acetonitrile is studied by UV-vis and U L(sub III) EXAFS spectroscopy. The investigations point to the existence of a [UO(sub 2)Cl(sub 4)](super 2-) species in solution with D(sub 4h) symmetry.

Double-mixing stopped-flow spectroscopy was employed to study the reactions of the two intermediate species [H.sub.peroxo] and Q with a panel of substrates of varying C-H bond strength in the bacterial enzyme monooxygenase. The reaction of [H.sub.peroxo] with acetonitrile appears to proceed by a distinct mechanism in which a cyanomethide anionic intermediate is generated and provide evidence in support of [H.sub.peroxo] as an electrophilic oxidant that operates via two-electron transfer chemistry.

An in situ generated catalyst were developed from readily available Ru[H.sub.2][(P[Ph.sub.3]).sub.4], an N-heterocyclic carbene (NHC) precursor, NaH, and acetonitrile. The prepared catalyst exhibited high activity for the amide synthesis directly from either alcohols or aldehydes with amines.

1,3-Dipolar cycloadditions of a series of 12 allyl-anion type 1,3-dipoles X[double bond][Y.sup.+]-[Z.sup.-] (X, Z = C[H.sub.2], NH, O; Y = N(Me), O) to acetonitrile MeC[double bond]N, both free and coordinated to [Pt.sup.II] and [Pt.sup.IV] in the complexes trans-[Pt[Cl.sub.n][(NCMe).sub.2]], are examined. The reaction mechanisms and correlations of activation and reaction energies, synchronicity and charge transfer vs dipole nature, FMO energies, atomic charges, HSAB properties, distortion energies and regioisomeric pathways are described.

The article discusses the synthesis and the characterization of an organometallic trinuclear niobium cluster complex in aqueous solution. The significance of the presence of the [Nb.sub.3]([mu]-[n.sup.2]:[n.sup.2]-NCC[H.sub.3])[([mu.sub.2]-O).sub.3.sup.6)] cluster core in such complexes is also demonstrated.

Several DFT/TDDFT calculations are conducted to explain the various solvatochromic and ionochromic effects of iron(II)bis(1,10-phenanthroline)dicyano complexes. The vertical excitation energies of the compounds are also determined.

Several studies are conducted to explain the synthesis, as well as the characterization of a new asymmetric, linear, trinuclear manganese(II) complex. The coordination of different ions in the compound is also discussed.

The synthesis of the bidentate ligand, 4',5'-ethylenedithiotetrathiafulvenyl[4,5-f][1,10]phenanthroline via the fusion of tetrathiafulvalene (TTF) and 1, 10-phenanthroline is discussed. The mechanisms associated with the unexpected oxidative cleavage of the C=C bond taking place in the ruthenium(II) complex of the compound are also explained.

A series of imines with various typical structures are prepared and the thermodynamic affinities of the imines to abstract hydride anions, hydrogen atoms and electrons, the thermodynamic affinities of the radical anions of the imines to abstract hydrogen atoms and protons and the thermodynamic affinities of the hydrogen adducts of the imines to abstract electrons in acetonitrile are determined. The studies have introduced the idea of a thermodynamic characteristic graph (TCG) of imines as an efficient oMolecule ID Cardo.

The optimization of the [F.sub.2] perfluorination of [K.sub.2][B.sub.12][H.sub.12] in acetonitrile with continuous bubbling of [F.sub.2]/[N.sub.2] has shown that HF and other protic acids have inhibited each of the fluorination steps and the fluorination has taken place at the gas bubble-solution interface. The DFT studies haves shown that these two phenomena are related by the relative propensities of [B.sub.12][H.sub.12-x][F.sub.x.sup.2-] anions to partition from bulk solution to the interface.

The article presents a comparative study of the electronic differences observed in the hydroxy and the dialkylamino substitutents in different bisarylethynylbenzenes. The anilium, as well as the phenol groups are shown to exhibit spectroscopic properties.

Gold(III) activation of unprotected propargyl glycosyl donors is effective for preparing of saccharides. Secondary alcohols are used but with diminished efficiency and the propargylic family of donors are convenient because they can be prepared on large scale by Fischer glycosylation and stored indefinitely before chemoselective activation by the catalyst.

The reaction of [alpha],[beta]-unsaturated carbonyl compounds with aminoacetonitrile hydrochloride has provided 3,5-disubstituted 3,4-dihydro-2H-pyrrole-2-carbonitriles in a one-pot reaction sequence. The main step has involved the thermal electrocyclization of a stabilized 2-azapentadienyl anion that is formed by condensation of the reactants and subsequent deprotonation.

The conventional conductometers as well as stopped-flow techniques were employed to determine the rate constants for solvolyses of benzhydryl chlorides, which take place on the 10 ms to minute time scale, in aqueous acetone and acetonitrile. The observed common-ion rate depressions were demonstrated by the correlation equation for electrophile-nucleophile combinations.

The article explains the various mechanisms that are involved in the selective oxidation of the aryl methyl sulfides, which is done in the presence of the catalysts like [HNO.sub.3] and [FeBr.sub.3]. The impact of the concentration of these compounds on the rate of reaction is also discussed.

The various effects of ionic base, catalysts and solvents on the multicomponent direct synthesis of the pyridine-3,5-dicarbonitriles are examined. The presence of a reaction intermediate is shown to facilitate the reaction more, as compared to the presence of an ionic base.

The reduction of IBX to IBA in the presence of molecular iodine in DMSO to generate hypoiodous acid (IOH), which reacted with a variety of olefins as well as [alpha],[beta]-unsaturated ketones leading to their respective iodohydrins with anti stereochemistry is reported. The same redox chemistry in acetonitrile containing TFA produced iodonium ions for facile iodination of a variety of aromatic compounds in respectable isolated yields.

The first set of C-NO bond homolytic and heterolytic dissociation enthalpies in solution is obtained by using direct titration calorimetry combined with appropriate electrode potentials through thermodynamic cycles. The homolytic bond dissociation energy scale (BDEs) of the corresponding C-NO bonds in the gas phase is calculated and the C-NO and S-NO bond thermodynamic parameters are used for predicting the trend of NO transfer from C-nitroso substrates to thiols in acetonitrile solution.

The B[F.sub.3].[Et.sub.2]O-induced decomposition of ethyl 2-diazo-3-hydroxy-3,3-diarylpropanoates, prepared by the addition of a series of benzophenones to ethyl diazo(lithio)acetate, is analyzed. Acetonitrile is used as a solvent for deriving the corresponding N-acyl [beta]-enamino ester derivatives with a diverse regioselectivity as the result of 1,2-aryl migration in the vinyl cation intermediates.

The dual ability of sodium hydride to behave as a base as well as a source of hydride, which could be applied as a common reagent for substrate activation in nucleophilic substitution reactions, is described. The structural nature of byproducts obtained from reaction of dimethylformamide or acetonitrile as solvents and benzyl bromide as an electrophile is also discussed.

A detailed study was carried out to understand the photochemistry of 6-bromo-2-naphthols in acetonitrile, aqueous acetonitrile, and isopropyl alcohol in the absence and presence of triethylamine. A more pronounced nature of the aryl radical of the carbene [super 3]5-C than the Grabner's carbene permits the generation of fairly efficient arylation/alkylation of aromatics and alkenes, through a radical-like pathway.

X-ray adsorption near edge structure (XANES) analysis is used for a metal-to-ligand charge-transfer (MLCT) excited-state structure of a copper(I) diimine complex ([[Cu[(dmp).sub.2]].sup.+] (dmp = 2,9-dimethyl-1,10-phenanthroline)) in acetonitrile. The XANES calculations have allowed angular dependent structural parameters to be extracted, which is vital for imaging reaction coordinate of many photochemical reactions.