The First Direct Synthesis of Corroles from Pyrrole

The solvent-free, catalyst-free condensation of pyrrole and aldehydes provides an extremely facile synthetic pathway to novel corroles [Eq. (1); Ar=C₆F₅, 2,6-F₂C₆H₃, 2,6-Cl₂C₆H₃]. The product containing pentafluorophenyl groups is an excellent precursor of other derivatives, including an ionic, water-soluble corrole.     

2-Hydroperfluoropropyl azide—a versatile reagent for the oxidative fluorination of organic compounds of trivalent phosphorus

2-Hydroperfluoropropyl azide CF₃CHFCF₂N₃, 1 , an inexpensive, readily available, and stable (easy to store) compound, is suggested as an effective fluorinating reagent for different classes of trivalent organophosphorus compounds in accordance with the general scheme R₃P → R₃PF₂. Generally, the reactions are performed without solvent, the highly volatile CF₃ CHFCN being the main by-product. The fluorination is usually an exothermic process, but slight heating is necessary in the case of alkyldifluorophosphites. The unusual Arbuzov rearrangement, accompanied by isomerization of an isobutyl or neopentyl group into a tert-group, ROPF₂ → t-R′POF₂, under the action of a catalytic amount of 1 , was observed.     

The direct synthesis of magnesium amides and the crystal structure of an unusual magnesium tert-butylamide

The magnesium amides Mg(NHi-C₃H₇)₂; Mg(N(C₂H₅)₂)₂ and Mg(NC₅H₁₀)₂ have been prepared by direct synthesis from magnesium and i-C₃H₇NH₂, (C₂H₅)₂NH or C₅H₁₀NH, respectively, at high temperature and under a pressure of hydrogen. When an excess of Mg was used MgH₂ was isolated, suggesting that magnesium hydride is an intermediate in this reaction.t-C₄H₉NH₂ gave two crystalline products, NMg₆(NHt-C₄H₉)₉ (I) and an insoluble material, probably (MgNR)_x. The structure of I was determined by X-ray crystallography.     

On the possibility of the existence of molecular nitrogen allotropes

The possibility of the existence of nitrogen molecules with an even number of atoms of composition N₄, N₆, N₈, and N₁₀ has been discussed with the use of the QCISD and G3 quantum-chemical methods. From these data, a conclusion has been made that three new nitrogen allotropes with an even number of atoms in a molecule can exist, namely, N₄ shaped as a rectangle and regular tetrahedron and N₆ with a shape remotely resembling an “open book.” The bond lengths and bond and torsion angles in each of these molecules have been reported.     

Investigation of the possible incorporation of protons into oxide cathodes during chemical delithiation

Chemical delithiation of layered LiCoO₂, LiNi_0.5Mn_0.5O₂, and Li₂MnO₃ and spinel LiMn₂O₄ cathodes have been investigated with both an acetonitrile (non-aqueous) solution of the oxidizer NO₂BF₄ and an aqueous acid. The products have been characterized by X-ray diffraction, wet chemical analyses for lithium and oxygen contents, infrared spectroscopy, and thermogravimetric analysis to determine whether or not protons are incorporated into the lattice during the delithiation process. While the delithiation in aqueous acid medium leads to an incorporation of protons into the layered oxide lattice, the non-aqueous delithiation with NO₂BF₄ does not involve any proton insertion into the lattice. In contrast to the layered oxides, the chemical delithiation of spinel LiMn₂O₄ even in the aqueous acid medium does not involve any proton insertion into the lattice.     

Molecular structures of inorganic compounds of low volatility: I. Salts of oxygen acids of the type M2XO4

We report an electron diffraction study of the molecular structure of gaseous cesium and thallium sulphates and cesium molybdate and tungstate. The average structure found for the M₂XO₄ molecules is described by a model (symmetry D_2d) in which the metal atoms bridge two edges of an XO₄ tetrahedron to form two 4-membered mutually perpendicular planar MO₂X rings.The data lead to conclusions on the complex nature of intramolecular motion. This motion may roughly correspond to great displacements of metal atoms on the surface of an imaginary sphere described near the tetrahedral acid residue.     

Effects of halo substituents on electron-impact induced fragmentation of cyclopropanes

Bromine, fluorine and/or chlorine atoms on one cyclopropyl ring jointly influence the dominant primary modes of electron-impact induced fragmentation. Decomposition ions include CBrX, C₂HQ₂X and C₃HQ₂X₂, where × is an halogen atom and Q is from the group of an halogen atom, an hydrogen atom and a methyl group. For none of the compounds studied was formation of an ionic CBrX the dominant primary process. Gem-dibromo-gem-dihalocyclopropanes preferentially eliminated dibromo divalent carbon and formed decomposition products of gem-dihalogenated C₂HQ₂X′s. In cases where more stable allyl ions were formed, fragmentation was through C₃HQ₂X₂. Upon electron-impact, the ions CF, CHF₂ and CF₃ were produced in abundances directly related to the fluorine content of their cyclopropyl precursors. When fragmentation patterns for internally generated radical ions of the composition C₂HQ₂X were compared with patterns obtained by direct introduction of the same fluoroolefins into a mass spectrometer, incomplete correspondence was found. Variation in the mode of decomposition can be a consequence of differences in the energy levels of the olefin fragmented. Addition of two hydrogen atoms from water to quinones and to s-tetrazines is well established in the literature. Reaction of an additional cyclic series, polyhalocyclopropanes, with water prior to electron-impact is suggested.     

A theoretical study of the elimination process of methane from a platinum complex

A theoretical analysis of the dissociative reaction cis-PtH(CH₃)(PX₃)₂ → Pt(PX₃)₂ + CH₄ is presented. Several aspects of the effect on the mechanism of this reductive elimination when the substituent X is changed (X₃  (CH₃)₃, case I and X₃  CH₂Cl(CH₃)₂, case II), are considered and compared with the corresponding experimental facts. This indicates the following: the kinetic barrier for case I is small and even if a concerted mechanism is implied, an almost spontaneous process is strongly indicated. The activation energy is lowered in case II, where the presence of an electronegative substituent makes even easier the performance of a spontaneous process. The study of the reaction pathway was carried out through an Extended Hückel calculation.     

Synthesis of functionally substituted methanofullerenes and study of their tribological properties

Possibility of synthesizing functionally substituted methanofullerenes by cycloaddition of diazo derivatives of methionine and threonine to C₆₀ fullerene in the presence of a three-component catalytic system Pd(acac)₂-PPh₃-Et₃Al was examined. Tribological characteristics of the resulting compound as an additive to an industrial oil were studied.     

Oxidation,Coordination, and Nickel-Mediated Deconstruction of a Highly Electron-Rich Diboron Analogue of 1,3,5-Hexatriene

The reductive coupling of an N-heterocyclic carbene (NHC) stabilized (dibromo)vinylborane yields a 1,2-divinyldiborene, which, although isoelectronic to a 1,3,5-triene, displays no extended π conjugation because of twisting of the C₂B₂C₂ chain. While this divinyldiborene coordinates to copper(I) and platinum(0) in an η²-B₂ and η⁴-C₂B₂ fashion, respectively, it undergoes a complex rearrangement to an η⁴-1,3-diborete upon complexation with nickel(0).     

Superior gas separation performance of dual-layer hollow fiber membranes with an ultrathin dense-selective layer

A concept demonstration has been made to simultaneously enhance both O₂ and CO₂ gas permeance and O₂/N₂ and CO₂/CH₄ selectivity via intelligently decoupling the effects of elongational and shear rates on dense-selective layer and optimizing spinning conditions in dual-layer hollow fiber fabrication. The dual-layer polyethersulfone hollow fiber membranes developed in this work exhibit an O₂/N₂ selectivity of 6.96 and an O₂ permeance of 4.79 GPU which corresponds to an ultrathin dense-selective layer of 918 Å at room temperature. These hollow fibers also show an impressive CO₂/CH₄ selectivity of 49.8 in the mixed gas system considering the intrinsic value of only 32 for polyethersulfone dense films. To our best knowledge, this is the first time to achieve such a high CO₂/CH₄ selectivity without incorporating any material modification. The above gas separation performance demonstrates that the optimization of dual-layer spinning conditions with balanced elongational and shear rates is an effective approach to produce superior hollow fiber membranes for oxygen enrichment and natural gas separation.     

Anodic dissolution of tin in alcohols

Tin(II) alcoholates Sn(OR)₂ are formed upon the anodic galvanostatic dissolution of tin in alcohols in an undivided cell in the presence of minimum amounts of NaOAc as an electrolyte. Tin(II) alcoholates are easily hydrolyzed in air to form oxyhydroxide Sn₃O₂(OН)₂ used as an anode or its composite component in lithium cells.

     

Investigation of the mechanism of hydridic reductions of carbon monoxide to hydrocarbons on iron complexes by isotopic labeling

The reduction of coordinated CO on Cp₂Fe₂(CO)₄ by LiAlH₄ has been investigated with isotopic labeling in an attempt to delineate the chain formation step. Reduction with LiAlD₄ resulted in formation of perdeutero-hydrocarbons. Reduction under an atmosphere of ¹³CO resulted in substantial incorporation of ¹³C into the hydrocarbon products. Reaction of the complexes RFeCp(CO)₂, R = CH₃, C₂H₅ and CH₃C(O), with LAD and with LAH under ¹³CO are reported. Reaction of CH₃ ¹³C(O)FeCp(CO)₂ with LAH is also reported. The results of these reactions suggest that chain extension occurs by a CO insertion reaction, probably by CO insertion into an alkylidene---metal bond.     

Synthesis and characterization of amminecopper hexamolybdometalates

Representatives of a new class of heteropoly compounds (HPCs) have been synthesized. Such an HPC is an oligomer, which is built of two monomeric 6-heteropolyanions with the Perloff structure; these monomers are linked through an amminecopper cation. The composition of the new HPCs is Cu(NH₃)₄ · ?ub;H[MMo₆O₁₈(OH)₆] · 10H₂O?ub;₂Cu(NH₃)₄, where M = Al(III), Cr(III), Fe(III), Co(III), Ga(III), or Rh(III). The compounds have been characterized using IR spectroscopy, thermogravimetry, and X-ray powder diffraction.     

Statistical experimental design-driven discovery of room-temperature conditions for palladium-catalyzed cyanation of aryl bromides

A combination of Pd₂(dba)₃·CHCl₃ (0.5 mol %) and commercially available, air-stable phosphonium salt [(t-Bu)₃PH]BF₄ (1.4 mol %) in a presence of Zn powder and Zn(CN)₂ as the cyanide source comprises an extremely efficient catalyst system for the cyanation of a diverse array of aryl bromides, at room temperature. This result emerged from an experimental strategy that combines the advantages of parallel, automated experimentation with the design of experiments (DOE) for the effective definition of an optimal set of reaction conditions.     

New Organosilicon Derivatives of Nitrogen-containing Heterocycles

Results are summarized of investigations carried out by the authors on the synthesis and study of the reactivity of organosilicon derivatives of nitrogen-containing heterocycles YCH₂SiX₃, where X = OMe, F, 1/3 (OCH₂CH₂)₃N; Y = a heterocyclic substituent linked by a CH₂ group with an endocyclic nitrogen atom or an exocyclic sulfur atom.     

Simultaneous polymerization and formation of polyacetylene film on the surface of concentrated soluble Ziegler-type catalyst solution

A direct method of simultaneously polymerizing and forming acetylene monomer to produce uniformly thin films of polyacetylene was investigated in terms of catalyst system, catalyst concentration, and polymerization temperature. The best catalyst was a Ti(OC₄H₉)₄–Al(C₂H₅)₃ system (Al/Ti = 3–4) and the critical concentration was 3 mmole/l. of Ti(OC₄H₉)₄. Below the critical concentration, only a solid or a powder was obtained. The configuration of the polymers obtained depends strongly upon the polymerization temperature. Thus an all-cis polymer was obtained at temperatures lower than ?78°C, whereas an all-trans polymer resulted at temperatures higher than 150°C. Observations either in an electron microscope by direct transmission or in a scanning electron microscope showed that the film is composed of an accumulation of fibrils about 200–300 Å in width and of indefinite length.     

Improvement of the cycle life of composite xerogel V<Subscript>2</Subscript>O<Subscript>5</Subscript>/C in aqueous LiNO<Subscript>3</Subscript> solution by addition of vinylene carbonate

The xerogel V₂O₅/C composite was synthesized by a sol-gel method, using the suspension of carbon black in the solution of crystalline V₂O₅ in hydrogen peroxide as the precursor solution. The Li⁺ intercalation/deintercalation reactions of the xerogel V₂O₅/C composite, used as an anode material of a two-electrode cell with an aqueous LiNO₃ solution as the electrolyte, was studied before and after the addition of vinylene carbonate (VC). Upon addition of vinylene carbonate in an amount of only l wt %, the coulombic capacity during galvanostatic cycling, instead of commonly observed permanent fade, displayed an initial increase and then a stable plateau.     

Hypervalent Iodine Oxidation of Hydrazine Hydrate in Dichloromethane. A New Method for Diimide Generation

Diimide reduction of olefins, an alkyne and an azo compound using C₅H₅I(OAc)₂/CH₂Cl₂ at room temperature is reported.