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The compound 2,6-dimethylmesitylene-2,6-diyl dication (2) has been prepared, characterized by nuclear magnetic resonance (NMR) spectroscopy and analyzed by DFT/IGLO. Basing on NMR data, a dienylic allylic dication system (2a) seems to be the major contributor to structure 2. DFT/IGLO theoretical NMR chemical shift computations provided excellent correlation with the experimental data. The combined experimental and theoretical procedure support structure 2a wherein the dienyl and allylic cation units are insulated from each other not unlike what is theoretically computed for the related benzene dication 3.

Two distinct novel polymeric silver(I) complexes containing tetracoordinated Ag+ centers are prepared by reacting 1,4-thioxane with silver triflate at ambient temperature. The molecular and crystal structures of the complexes are then examined by infrared spectroscopy and nuclear magnetic resonance measurements. Results show that the two polymeric complexes have excellent coordination to two sulfur and two oxygen ligands.

Reaction between a fluorosulfuric acid and a tetraol precursor results in the formation of 1,3,5,7-adamantanetetrakis(alpha,alpha-diphenylmethyl)tetrayl tetracation. NMR spectra reveals that adamantane maintaineds its tetrahedral symmetry upon ionization. The tetracation, from -80 degree Celsius to -40 degrees Celsius, is stable. Delocalization of positive charge into the phenyl group is essential to compensate for additional charge-charge repulsion.

A 1H and 13C NMR spectroscopic investigation of the o-methyl, m-methyl and m-tert-butyl derivatives of 1,1-di-1-adamantylbenzyl cations is presented. The results showed that o-tolyldi-1-adamantylmethyl has the most deshielded carbocationic centers for a tertiary benzylic cation in solution. The steric effect virtually excludes p-pi resonance overlap with the adjacent empty p-orbital. However, the lack of resonance stabilization is compensated by the hyperconjugative contributions from the two adamantyl groups.

Gold can be used to synthesize analogues of many gitonic dications, formed as temporary intermediates in the reactions catalyzed by superacids. The analogue of the diprotonated water, (H4O)2+, is formed by using an Au(I) fragment as an isolobal substitute for H+. Au analogues of CH5+, CH6+, diprotonated methane, and NH5+ have also been prepared. Although these gitonic dications are unstable, the Au analogues are stable due to Au-Au binding.

Electrochemical methods enable the conversion of the commercially available tetrachlorocyclopropene into hexakis(trimethylsilyl)-3, 3'-bicyclopropenyl. Analysis of the electrochemical reaction between tetrachlorocyclopropene and chlorotrimethylsilane reveals the occurrence of first two trimethylsilylations at the vinylic positions. The tris(trimethylsilyl)cyclopropenyl radical undergoes a radical coupling reaction after the incorporation of the third trimethylsilyl group, producing the bicyclic product.

Nitrosonium tetrafluoroborate and pyridinium polyhydrogen fluoride (PPHF) reagent system function as F2 equivalent reagent in the direct one-step fluorination of diarylacetylenes to diaryltetrafluoroethanes. Fluorination of 1-phenyl-1-butyne by this system leads to the formation of 1-phenyl-1,1,2,2-tetrafluorobutane and 1-phenyl-1,1, 2-trifluoro-2-butene. Mechanistic study reveals the initial formation of NOF, followed by addition, protonation and nucleophilic displacement steps.

Ionization of the associated 1,3'-spirocyclopropylbicyclo(2.2.2)octan-2'-ol facilitated the synthesis of the stabilized 1,3'-spirocyclopropylbicyclo(2.2.2)oct-2'-yl cation which was not noticeable. Generation of the allylic 2-methylbicyclo(3.2. 2)non-3-en-2-yl cation resulted from smooth alignment.

Investigations confirm phenyl azide/triflic acid as an extremely good reagent for the high yield electrophilic phenylamination of aromatics. Diarylamines process application as intermediates for the preparation of spiroacridins, acridine, phenazines and carbamazepine. Excess triflic acid probably proto-solvates the phenylaminodiazonium ion, increasing its electrophilicity.

Investigations focus on the importance of, and prove the existence of protoalleane dications in solution, and offer experimental and theoretical proof in the instance of the tert-butyl cation. The protio-tert-butyl dication may be a part of the C-scrambling observed. Besides liquid superacidic systems, protosolovation can be important in solid systems, in which the acid regions are grouped. Secondary or primary alkyl chains are less stable, but more reactive electrophiles than tert-alkyl cations such as the tert-butyl cation.

The synthesis of the 1-ferrocenyl-1-cyclopropyl cation under superacidic conditions and with the carbocationic center stabilized by the adjoining ferroncenyl moiety is presented. A dark green solution results from the dissolution of 1-ferrocenyl-1-cyclopropyl trimethylsilyl ether in FSO3H/SO2ClF at -78 degrees C. Increasing the temperature to -40 degrees C in the NMR probe for 8 min then recooling to -60 degrees C results in the desired complex.

Highlights: [•] BF3–H2O, a non-oxidizing conjugate Brønsted acid system plays a dual role, as an efficient catalyst as well as a good solvent for acid catalyzed reactions. [•] Many reactions which require superacidic conditions occur smoothly in BF3–H2O. [•] Application of BF3–H2O is extended toward the synthesis of perimidines and 1,5-benzodiazepines under mild conditions. [ABSTRACT FROM AUTHOR]

Abstract: Commercially available Sn particles mixed with Nafion® ionomer are used to prepare an electrode with a gas diffusion layer support in a manner similar to that in which fuel cell electrodes are prepared. Cyclic voltammetry is performed in aqueous NaHCO3 (basic medium) on the electrode and the Tafel parameters are obtained and compared with a Sn metal disc and with a graphite disc coated with Sn powder. In addition, electrolysis is carried out potentiostatically, also in NaHCO3 solution, at various potentials. The exchange current density on the Sn/gas diffusion layer electrode shows to be two orders of magnitude higher that on the metallic Sn disc. The maximum current density obtained during electrolysis is 27 mA cm−2 at −1.6 V vs. NHE, with 70% faradaic efficiency towards the formation of formate, which is one of the highest values found in the literature on Sn electrode at ambient pressure. [Copyright &y& Elsevier]

Abstract: α-Fluoromethyl phenyl sulfone derivatives have been extensively employed in various reactions as versatile fluoromethylating reagents. While nucleophilic monofluoromethylations of aldehydes have been achieved using fluoromethyl phenyl sulfone or fluorobis(sulfonyl)methanes, a facile protocol under mild reaction conditions remains an ardently sought goal. We now report a feasible synthetic approach toward β-monofluorinated alcohols using α-trimethylsilyl-α-fluorobis(phenylsulfonyl)methane [TMSCF(SO2Ph)2, TFBSM] as a novel monofluoromethylating reagent. Initiated by a catalytic amount of fluoride, the reagent can be readily added to a variety of aldehydes providing the desired products in high yields. Computational and kinetic studies have revealed the exceptional lability of the Si–C bond in TFBSM compared with other fluoromethylsilane counterparts. [Copyright &y& Elsevier]

Abstract: γ-MnO2 nanoparticles-coated polyaniline (PANI) nanofibers on carbon electrode were prepared by potentiodynamic electrochemical deposition of PANI and MnO2 from a single pot. Higher thermal stability of the resulting nanocomposites and their activity for formic acid oxidation permits the realization of a platinum-free anode for formic acid fuel cells. [Copyright &y& Elsevier]

Abstract: A fluoride-induced nucleophilic (phenylthio)difluoromethylation method using TMS–CF2SPh has been achieved. This new methodology efficiently transfers “PhSCF2” group into both enolizable and non-enolizable aldehydes and ketones to give corresponding (phenylthio)difluoromethylated alcohols in good to excellent yields. Diphenyldisulfide can also be (phenylthio)difluoromethylated into PhSCF2SPh in high yield. The reaction with methyl benzoate, however, gives only low yield of (phenylthio)difluoromethyl phenyl ketone. The above-obtained PhSCF2-containing alcohols can be further transformed into difluoromethyl alcohols using an oxidation–desulfonylation procedure. This new type of nucleophilic (phenylthio)difluoromethylation methodology may have other potential applications in the medicinal and agrochemical fields. [Copyright &y& Elsevier]

A new and efficient method for the preparation of tri- and difluoromethylsilanes using magnesium metal-mediated reductive tri- and difluoromethylation of chlorosilanes is reported using tri- and difluoromethyl sulfides, sulfoxides, and sulfones. The byproduct of the process is diphenyl disulfide. Since phenyl trifluoromethyl sulfone, sulfoxide, and sulfide are readily prepared from trifluoromethane (CF[sub 3]H) and diphenyl disulfide, the method can be considered to be catalytic in diphenyl disulfide for the preparation of (trifluoromethyl)trimethylsilane (TMS-CF[sub 3]) from non-ozonedepleting trifluoromethane. [ABSTRACT FROM AUTHOR]

Isomeric 1- and 3-isoquinolinols (11 and 12) when activated in CF[sub 3]SO[sub 3]H-SbF[sub 5] acid system undergo selective ionic hydrogenation with cyclohexane to give 5,6,7,8,tetrahydro-1(2H)- and 5,6,7,8tetrahydro-3(2H)-isoquinolinones (22 and 27). Under the influence of aluminum chloride similar products were also obtained along with 3,4-dihydro-1(2H)- and 1,4-dihydro-3(2H)-isoquinolinones (23 and 28), respectively. Compounds 11 and 12 also condense with benzene in the presence of aluminum halides, under mild conditions, to give 3,4-dihydro-3-phenyl-l(2H)- and 1,4-dihydro-1phenyl-3(2H)-isoquinolinones (24 and 29), respectively. Prolonged reaction time or catalysis under strongly acidic HBr-AlBr[sub 3] provides an alternative reaction pathway to yield 5,6-dihydro-6,8diphenyl-1(2H)- and 5,6,7,8-tetrahydro-6,8-diphenyl-3(2H)-isoquinolinones (25 and 30), respectively. Products 24 and 29 were also found to revert back to 11 and 12 in the presence of aluminum halides in o-dichlorobenzene. The mechanism of these intriguing reactions, which involves superelectrophilic dicationic intermediates, is discussed. [ABSTRACT FROM AUTHOR]

Electronic structures and energies of superelectrophilic dications derived by protonation of methyland dimethylmethyleniminium (R'R'C=N[sup +]R'R'; R', R' = CH[sub 3] or H) ions were calculated at the ab initio MP2/6-311+G[sup **] level. The calculations identified the N-protonated isopropyleniminium dication 14 as a minimum structure. On the basis of computed energies, deprotonation energies of the global minimum structures were also calculated. The [sup 13]C NMR chemical shifts of the intriguing dication 14 were calculated using the GIAO-MP2 method. The [sup 13]C NMR chemical shifts of the isoelectronic analogue tert-butyl cation were also calculated at the same level in order to explore the effect of an additional charge in dications 14. [ABSTRACT FROM AUTHOR]

Examines the density functional theory of chemical compounds. Stabilization of tri(amino)amine dication with high kinetic barrier for deprotonation; Calculation on the energetics related to mixed amino(azido)ammonium ions; Stability of thermodynamic interaction.

Focuses on calculation of structures and stabilities of higher coordinate onium-boronium dications by ab inition method. Composition of the dications; Computation of thermodynamics of the complexations of 1-4a and H[sub2] to form 1-4d.

Examines the calculated structures and chemical shift relationship in hypercoordinate onium-carbonium dications and isoelectronic onium-boronium cations. Correlation between carbon and boron chemical shifts; Factors that determine the chemical shift of boron nuclei; Details on the structures of protonated borane-Lewis base complexes.

Discusses findings of an ab initio study of the structures and stabilities of the dimer of ethyl cation and related isomers. Total and relative energies; Different dissociation paths for the global minimum structure.

Investigates the structures and stabilities of gitonic and distonic alkanonium dications. Dissociation pathways for the dications; Role of demethylation in the dissociation process; Global minimum energy structures of the C[sub n]H[sub 2n+4][sup 2+] dications.

Reports on the preparation of tris(trimethylsilyl)sulphonium and methylbis(trimethylsilyl)sulphonium ions as long-lived species by reacting trimethylsilane and trityl tetrakis(pentafluorophenyl)borate in the presence of precursor sulfides. Characterization by [sup 1]H, [sup 13]C and [sup 29]Si nuclear magnetic resonance spectroscopy.

Focuses on a paper conducted on the comparison of energies and structures of CH... and CH... and their role in superacidic methane activation. Effect of the protonation of methane to CH... on the formation of CH...; What subsequent reaction with neutral methane while reforming CH... reveal.

Discusses the different procedures for producing derivative synthetic materials from silicon-assisted perfluoroalkylation of organic compounds. Methods of preparation for perfluoroalkylated organosilicon compounds; Perfluoroalkylation reactions; Synthetic applications of trimethylsilanes.

Reports on the preparation and use of fluoroalkylating agents of the general formula trimethylsilane, difluorobis-methane and tetrafluoro-ethane. Analysis of the structure of tetrafluoro-ethane by x-ray diffraction; Difluorobis(trimethylsilyl)methane as an `in situ' source for the perfluorovinyl anion.

Determines the energies, electronic structures, and gas phase proton affinities of a series of protodiazonium and bisdiazonium dications and their parent diazonium ions. Decomposition barriers of dications; NMR chemical shifts; Potential role of protodiazonium dications in superacid chemistry.

Investigates experimental and theoretical investigation of the cleavage reaction of trifluoroacetic acid in superacids. Correlation of calculated fluorocarbons; Intermediates in the electrophilic addition to fluoroolefins; Destabilizing property of a fluorine atom; Nuclear magnetic resonance spectroscopy under superacid stable ion conditions.

Studies the structures and energies of mono-, di-, and triprotonated urea. Chemical shifts; Site of protonation of urea; Prototype gitonic onium dication.