Density functional study on the bromination of heteroelement-substituted acetylenes

The reactions of heteroelement-containing alkynes H₃SiC≡CH and R₃MC≡CPh [R₃M = H₃Si, Et₃Si, Et₃Ge, (MeO)₃Si, (EtO)₃Ge, N(CH₂CH₂O)₃Si, N(CH₂CH₂O)₃Ge, Bu₃Sn] with one and two bromine molecules were studied in terms of the density functional theory. Transition states along reaction channels leading to products of both addition at the triple bond (cis- and trans-dibromoalkenes and 1,1-dibromoalkenes) and cleavage of the M-C≡ bond were localized.     

Half-sandwich trihydrido ruthenium complexes

This paper reports facile preparation of half-sandwich trihydrido complexes of ruthenium based on the reactions of the readily available precursors [Cp(R₃P)Ru(NCCH₃)₂][PF₆] with LiAlH₄. The target complexes were characterized by spectroscopic methods and X-ray structure analysis of .     

4-Ferrocenyl-2-fluorophenylboronic acid: synthesis and structure

Russian Chemical Bulletin - 4-Ferrocenyl-2-fluorophenylboronic acid was obtained from ferrocene in two steps. In crystal, this compound forms a dimer due to the O–H...O hydrogen bonds and...     

Preparation and properties of dicyclopentadienylniobium(III) chloride

The preparation of an air-sensitive 16-electron complex, Cp₂NbCl, is described. Its main property is easy transformation to 18-electron mononuclear compounds. Cp₂Nb(=O)Cl and Cp₂Nb(CO)Cl are obtained in oxidation and carbon monoxide gas addition processes, respectively. The physical properties of these complexes are described.     

Solvent and concentration effects on the properties of electrospun poly(ethylene terephthalate) nanofiber mats

This study describes the preparation and characterization of nanofibrous mats obtained by electrospinning poly(ethylene terephthalate) (PET) solutions in trifluoroacetic acid/dichloromethane (TFA/DCM). Special attention was paid to the effect of polymer concentration and solvent properties on the morphology, structure, and mechanical and thermal properties of the electrospun nonwovens. The results show that the spinnable concentration of PET solution in TFA/DCM solvents is above 10 wt %. Mats have nanofibrous morphology with fibers having an average diameter in the range of 200–700 nm (depending on polymer concentration and solvent composition) and an interconnected pore structure. Higher solution concentration favors the formation of uniform fibers without beads and with higher diameter. Morphology and fiber assembly changed with the solvent properties. Solvent mixtures rich in TFA, i.e., those with higher dielectric constant and lower surface tension, originated fibers with small diameter. However, due to the lower volatility, those solvent mixtures also produced more branched and crosslinking fibers, with less morphologic uniformity. Mechanical properties (Young's modulus, ultimate strength, and elongation at break) and thermal properties (glass transition, crystallization, and melting) have been studied for the PET electrospun nanomats and compared with those of the original polymer. Solvent effect on fiber crystallinity was not significant, but a complex effect was observed on the mechanical properties of the electrospun mats, as a consequence of the different structural organization of the fibers within the mat network. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 460–471, 2008     

H NMR Spectra and electronic structure of binuclear niobocene and titanocene containing fulvalene ligands

¹H NMR spectra of binuclear metallocene hydride complexes, (η⁵ : η⁵-C₁₀H₈)(C₅H₅)₂M₂(μ-H)₂ (M = Nb, 20°C and Ti, (−60 to +25°C), were studied. The Nb complex is diamagnetic and gives a high resolution spectrum. The coordination of bridging hydride H atoms provides Nb atoms with complete 18 electron configuration. In its ground state, the Ti complex is also diamagnetic (the spectrum at −60°C agrees to that) in spite of only 17 electron configuration of each Ti atom. However, the population of the excited triplet state in the case of the Ti complex is appreciable at temperatures higher than −30°C, the proton resonance lines being shifted downfield and significantly broadened as compared with the spectrum at −60°C.     

龙爪芦荟和库拉索芦荟中微量锗的测定与红外光谱区别

采用吸光光度法对龙爪芦荟和库拉索芦荟中的微量锗进行了测定,并探讨了两种芦荟的红外光谱的区别。结果表明,龙爪芦荟中含锗量在26.1～28.6μg·g-1,回收率为91.6%～97 5%。库拉索芦荟中含锗量在16.8～20.0μg·g-1,回收率为87.1%～94.5%。两种芦荟的FT IR光谱图在2100cm-1处有明显差异,由此可区别两种芦荟。     

Synthesis of substituted 1-acyl-1′-biphenylylferrocenes. Crystal structures of 4-bromo-4′-ferrocenylbiphenyl and 1-(4′-cyanobiphenyl-4-yl)-1′-((<Emphasis Type="Italic">S</Emphasis>)-3-methylpentanoyl)ferrocene

Acylation of 4-bromo- and 4-cyano-4-ferrocenylbiphenyl with alkanoyl chlorides afforded the corresponding 1-acyl-1-biphenylylferrocenes in 20% yields. X-ray diffraction study of the above-mentioned bromo derivative and 1-(4-cyanobiphenyl-4-yl)-1-((S)-3-methylpentanoyl)ferrocene demonstrated that these ferrocenylbiphenyl derivatives crystallize in noncentrosymmetric space groups.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1864–1870, September, 2004.     

Mass spectrometry of π-complexes of transition metals : X. Methylferrocene

The study of deuterium labelled methylferrocenes has shown the ions C₁₁H₁₁Fe⁺, C₆H₆Fe⁺, C₅H₆Fe⁺ to originate from the isomerised form of the molecular ion in which all the hydrogen atoms are redistributed among the ligands.