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Masaaki Ichinohe Kaori Sanuki Shigeyoshi Inoue Akira Sekiguchi 《Silicon Chemistry》2007,3(3-4):111-116
The reaction of dilithiosilane, ( t Bu2MeSi)2SiLi2 (2), with 1,1,2,2-tetrachloro-1,2-dimesityldisilane produced the tetrasila-1,3-butadiene derivative, ( t Bu2MeSi)2Si=Si(Mes)–(Mes)Si=Si(SiMe t Bu2)2 (3, Mes = 2,4,6-trimethyl-phenyl), which was isolated as reddish-purple crystals. The structure of 3 was determined by both spectroscopic and crystallographic methods; the Si=Si double bond lengths are 2.2003(12) and 2.1983(12) Å, and the length of the central Si?Si single bond is 2.3376(11) Å. The tetrasilabutadiene moiety is highly twisted, the torsional angle of Si1=Si2?Si3=Si4 being 72°. The reaction of 3 with t BuLi or KC8 in THF gave the disilenyllithium 4 and disilenylpotassium 5, which contain an sp 2-type silyl anion, by the reductive cleavage of the central Si–Si bond in 3. 相似文献
325.
The long story of aromatic compounds has extended over almost two centuries, since the discovery by Faraday of "bicarburet of hydrogen", or C(6)H(6), now called benzene. Since then, the chemistry of aromatic compounds has been developed extensively; this is reflected in the synthesis of novel classes of aromatic derivatives including charged species, nonclassical (M?bius, three-dimensional, homo-, metalla-) aromatics, and fullerenes. The theory of aromaticity has also undergone a spectacular evolution since the first definition of aromaticity by Hückel; the classification of aromaticity now requires the consideration of versatile criteria: energetic, structural, magnetic, among others. In this Review, we discuss the current state of affairs in the chemistry of aromatic compounds of the heavier Group 14 elements, the latest experimental achievements, as well as future prospects in the field. 相似文献
326.
Cyclic polyenes, such as benzene, cyclopentadienyl and cyclobutadiene, are widely used as key ligands for a variety of transition-metal complexes. The heavy versions of these compounds, in which the skeletal carbon atoms are fully (or partially) replaced with heavy group 14 elements (Si, Ge, Sn and Pb) were not synthetically accessible until quite recently. However, they are now readily available following the pioneering discoveries of derivatives of sila- and germabenzenes, sila- and germacyclopentadienide ions and tetrasila- and disiladigermacyclobutadiene dianions. Apart from their undoubted structural and synthetic interest, such organometallic compounds are particularly important as the precursors of novel ligands for new-generation transition-metal complexes, and this is covered in this critical review (124 references). 相似文献
327.
Y Sekiguchi A Nishikawa H Makita A Yamamura K Matsumoto N Kiba 《Analytical sciences》2001,17(10):1161-1164
A flow sensor with immobilized oxidases is proposed for the determination of histamine in fish meat. Chemiluminometric measurement of histamine was based on the luminol reaction with hydrogen peroxide produced by immobilized histamine oxidase (EC 1.4.3.-.) and peroxidase (EC 1.11.1.7.) within a flow cell. Histamine oxidase was found in cells of Arthrobacter crystallopoietes KAIT-B-007 isolated from soil. The oxidase and peroxidase were coimmobilized covalently on tresylated hydrophilic vinyl polymer beads and packed into transparent PTFE; the tubing was used as the flow cell. One assay for histamine was done at intervals of 2 min without carryover. The calibration curve for histamine was linear from 0.1 microM to 50 microM. The response was reproducible within 1.25% of the relative standard deviation for 115-replicate injections of 50 microM histamine. The sensor system was applied to the determination of histamine in fish meat extracts. 相似文献
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Osamu Sekiguchi Susumu Tajima 《Journal of the American Society for Mass Spectrometry》1997,8(8):801-808
The metastable decompositions of the molecular ions of methyl thioglycolate (1) and ethyl thioglycolate (2) were investigated by means of mass analyzed ion kinetic energy (MIKE) spectra and deuterium labeling. The loss of methanol is the only metastable decomposition of 1+·. This fragmentation occurs via two distinct pathways. The molecular ions of 2 decompose in a variety of ways, i.e., the losses of water, ethene, ethanol or ?2H3O2. All of these decompositions, except the loss of ethene, occur through two distinct mechanisms. During the loss of ?2H3O2, the ethyl group or ethene migrates from the oxygen to the sulfur atom. The loss of H?S, which corresponds to the loss of H?O with a concomitant double hydrogen transfer observed in the case of methyl glycolate (3), does not participate in the metastable decomposition of 1+· and 2+·. This is due to the energetic favorableness of the loss of methanol. 相似文献
330.
Akira Sekiguchi Tsukasa Matsuo Hideki Sakurai 《Angewandte Chemie (International ed. in English)》1998,37(12):1661-1664
A highly symmetric structure is displayed in toluene by 1 , which was obtained by reduction of octasilyl[4]radialene with lithium in THF. The two Li+ ions of 1 are not fixed to the π-electron system in toluene, but are fluxional, giving rise to a bis-contact ion pair. In a solvating medium such as THF, one of the Li+ ions dissociates in such a way that 1 exists as a contact ion pair and a solvent-separated ion pair. 相似文献