NEW RING SYSTEMS OF ELEMENTS OF MAIN GROUPS IV AND V

Abstract

The synthesis of [PhSn(O)O₂CC₆H₁₁]₆ represents the first example of tin(IV) in a drum-shaped molecule. The formation of the dimeric composition, [(MeSn(O)O₂CC₆H₁₁)₂(MeSn(O₂CC₆H₁₁)₃]₂, appears to be an intermediate hydrolysis product on the way to the drum composition. The X-ray structure reveals an “unfolded” drum array. The distannoxane unit which is represented as the sides of the drum is found in additional new dimeric compositions, [(SCH₂CH₂O)₂SnCl]₂[H][Et₄N], [((CN)₂C₂S₂)₂SnOH]₂, and [BuSnCl₂(OH) · H₂O]₂. These all have six-coordinated tin atoms which contrasts to the dimeric aryl distannoxanes recently isolated, [Ph₂(Cl)SnOSnPh₂(X)]₂, X = OH, Cl, containing five-coordinated tin. Also isolated are the new ring containing, five-coordinated tin derivatives, [(SCH₂CH₂S)₂Sn]₂[SCH₂CH₂S][Et₃NH]₂ and [(SC(CN)C(CN)S)₂SnMe][Et₄N]. The former has two trigonal bipyramidal tin atoms while the latter composition has a square pyramidal geometry. Related ring systems of new five-coordinated derivatives of silicon, germanium, arsenic, and antimony that span the range between the two ideal five-coordinated geometries also have been structurally characterized.     

Electron delocalization and aromaticity variations in the stacked nucleic acid base pairs

A newly developed exchange-correlation functional (MPWB1K) in density functional theory has been applied to evaluate the electron delocalization of individual fragments in the stacking interaction between nucleic acid bases (NABs). Electronically and structural-based indices have been employed to investigate the aromaticity variation during stacking interaction. A quantitative study of NABs in their isolated and stacked forms reveals that stacking interaction causes a decrease in bond delocalization. It is shown that the decrease in the aromaticity is accompanied by local decrease in two-center delocalization indices within the pyrimidine rings. We found that the aromaticity exhibits a similar trend for NABs in both their isolated and stacked forms. Moreover, it is indicated that aromatic fluctuation index is more sensible index to delineate the aromaticity variation during stacking interaction.

     

Products of resolvents and multivalued hybrid mappings in CAT(0) spaces

In this article, we introduce and investigate the concept of multivalued hybrid mappings in CAT(0) spaces by using the concept of quasilinearization. Also, we present a new iterative algorithm involving products of Moreau-Yosida resolvents for finding a common element of the set of minimizers of a finite family of convex functions and a common fixed point of two multivalued hybrid mappings in CAT(0) spaces.     

Synthese und Kristallstrukturen der Phosphaniminato-Komplexe [SnI(NPPh3)]2 und [SnI3(NPPh3)]2

Synthesis and Crystal Structures of the Phosphoraneiminato Complexes [SnI(NPPh₃)]₂ and [SnI₃(NPPh₃)]₂ The phosphoraneiminato complex of the divalent tin, [SnI(NPPh₃)]₂ ( 1 ), originates from the reaction of metallic tin with N-iodine triphenylphosphaneimine, INPPh₃, in dichloromethane suspension. 1 forms yellow, moisture sensitive crystals, which can be converted into the red phosphoraneiminato complex of the tetravalent tin, [SnI₃(NPPh₃)]₂ ( 2 ), by oxidation with iodine. According to the crystal structure analyses 1 and 2 have centrosymmetric dimeric molecular structures in which the tin atoms are linked via the N atoms of the NPPh₃^– groups. The tin atoms in 1 have a ψ-tetrahedral coordination, those in 2 a trigonal-bipyramidal one. 1 : Space group P 1, Z = 1, lattice dimensions at –80 °C: a = 779.0(1), b = 1080.1(1), c = 1170.4(1) pm, α = 64.49(1)°, β = 88.42(1)°, γ = 79.13(1)°, R = 0.0293. 2 : Space group P2₁/n, Z = 2, lattice dimensions at –80 °C: a = 1252.4(1), b = 1421.3(3), c = 1260.1(1) pm, β = 108.50(1)°, R = 0.0518.     

Recent progress in electrospun nanofibers: Reinforcement effect and mechanical performance

Composite materials are becoming increasingly important as structural materials for aeronautical and space engineering, naval, automotive, and civil engineering, sporting goods, and other consumer products. Fiber‐based reinforcement represents one of the most effective manufacturing strategies for enhancing the mechanical strength and other properties of composite materials. Electrospinning has gained widespread interest in the last two decades because of its ability to fabricate continuous ultrafine nanofibers with unique characteristics. The impact of electrospinning on fiber synthesis and processing, characterization, and applications in drug delivery, nanofiltration, tissue scaffolding, and electronics has been extensively studied in the past. In this article, the authors have focused on a comprehensive review of the mechanical performance and properties of electrospun nanofibers as potential reinforcements as well as their advanced nanocomposites. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1171–1212     

Biaryl formation via Suzuki and Stille coupling reactions using palladium nanoparticle/polymeric N‐heterocyclic carbene grafted silica as recyclable and efficient catalyst

Palladium nanoparticles supported on polymeric N‐heterocyclic carbene grafted silica as an efficient organic–inorganic hybrid catalyst is introduced. Pd⁰ nanoparticle formation, which is stabilized by the polymeric N‐heterocyclic carbene ligands and ionic liquid units, was confirmed using X‐ray photoelectron spectroscopy. Scanning electron microscopy images showed microparticles of modified silica while transmission electron microscopy images displayed a fine distribution of Pd nanoparticles. The modified structure was applied successfully in biaryl formation via Suzuki and Stille coupling reactions. Various biaryls were generated through the reaction of phenylboronic acid or tetraphenyltin with a variety of haloarenes via cross‐coupling reactions. This catalyst showed promising activity after being recycled several times. Copyright © 2016 John Wiley & Sons, Ltd.     

Corrosion resistance of electroless Cu–P and Cu–P–SiC composite coatings in 3.5% NaCl

The Cu–P and Cu–P–SiC composite coatings on carbon steel substrates were deposited via electroless plating. The anti-corrosion properties of Cu–P and Cu–P–SiC coatings were studied in 3.5% NaCl solution. The anti-corrosion properties of Cu–P and Cu–P–SiC coatings were investigated in 3.5% NaCl solution by the weight loss, potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS) techniques. It has been found that the shift in the corrosion potential (E_corr) towards the noble direction, decrease in the corrosion current density (I_corr), increase in the charge transfer resistance (R_ct) and decrease in the double layer capacitance (C_dl) values indicated an improvement in corrosion resistance with the incorporation of SiC particles in the Cu–P matrix. The effects of varying the SiC concentration on the corrosion resistance of carbon steel were investigated and it was found that the best anti-corrosion property of Cu–P–SiC is at 5 g L^?1 SiC in the bath formulation.     

An Easy One-Pot Procedure for the Synthesis of N -Sulfonyl Phosphorous Ylides and Sulfonyl Iminophosphoranes

Reaction of triphenylphosphine and an electron deficient acetylenic ester in the presence of strong N–H acid such as alkyl and aryl sulfamides or acetamide produces phosphorous ylides at room temperature in CH₂Cl₂. The aryl sulfamide phosphoranes undergo a smooth transformation reaction in boiling toluene and produce iminophosphoranes.