共查询到20条相似文献,搜索用时 316 毫秒
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硅氢加成催化剂的研究进展 总被引:7,自引:0,他引:7
硅氢加成反应是有机硅化学中研究得最多、应用较广的一类反应 .通过该反应 ,可以制得许多用其它方法难以得到的含官能基的有机硅单体或聚合物 .自 1 947年 Sommer等[1] 发现该反应以来 ,已进行了大量的研究工作 ,特别是对过渡金属催化剂的研究 ,取得了很大进展 [2 ,3] .我们将概要介绍这一领域的最新进展 .1硅氢加成的催化剂硅氢加成反应一般要在催化剂存在下才能进行 .紫外线、γ-射线、高温、过氧化物、偶氮化合物都可使该反应进行 ,但由于选择性不高 ,尤其是在一些体系中难以避免发生不饱和化合物的聚合反应 ,使用时受到许多限制 ,现已… 相似文献
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金属有机导体、半导体和超导体 总被引:2,自引:0,他引:2
本文综述了三类金属有机固体化合物的合成、结构与导电性能。这三类化合物是金属有机电荷转移盐,金属酞菁和会属卟啉络合物,以及金属有机夹层化合物。 相似文献
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Bogdan Marciniec 《Silicon Chemistry》2002,1(3):155-174
Recent progress in the catalytic hydrosilylation of organic and organosilicon compounds containing carbon-carbon multiple bonds is reviewed. Related to this, dehydrogenative silylation is also discussed. During the last decade new hydrosilylation catalysts, predominantly homogenous and heterogenous transition methal complexes, have been developed. These catalysts offer not only increased efficiency and turnover rate but also improved regioselectivity and stereoselectivity; moreover, there has been development in the mechanistic rationale behind these improvements. Application and extension of these basic chemical advances are found in many areas including polyorganosiloxane curing, hydrosilylation polymerization, polysiloxane functionalization, and silicon-containing dendrimer development. 相似文献
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以低活性含硅聚硼氮烷为先驱体,经熔融纺丝,BCl3脱硅不熔化处理以及在氨气气氛中高温裂解制备的氮化硼纤维仍含有硅元素,这主要是含硅聚硼氮烷结构中的B-N(SiMe3)2和B-N(SiMe3)-B由于位阻与BCl3反应脱除SiMe3不完全所致.而采用HCl首先与含硅聚硼氮烷反应减少其位阻,再通过BCl3进一步脱硅不熔化处理制备的氮化硼陶瓷纤维经FT-IR、X射线衍射(XRD)分析表明纤维基本不含硅元素,并且扫描电子显微镜(SEM)表明得到的氮化硼陶瓷纤维直径约为11μm,断面致密无孔,室温下抗拉强度为0.45GPa. 相似文献
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Silica-supported mono-metal (such as Ni, Cu) complexes and mixed metal (such as Cu/Zn, Cu/Cr) complexes of chitosan have been prepared. It is found that these non-noble metal complexes could be used as efficient catalysts for the hydrogenation of aromatic nitro compounds. The effects of type of metal, reaction temperature and pressure, solvent, nitrogen/metal molar ratio in the complex catalysts on the yields from nitrobenzene to aniline have been examined. It was also found that catalysts are active for the catalytic hydrogenation of other aromatic nitro compounds such as 2-nitroanisole, 2-nitroaniline, 2-nitrotoluene and 1-chloro-4-nitrobenzene. 相似文献
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Jack Halpern 《Angewandte Chemie (International ed. in English)》1985,24(4):274-282
Stable organometallic compounds, notably of the later transition metals (groups VI–VIII), usually are characterized by closed shell electron configurations (typically 18-electron valence shells) which are destabilized by electron addition or removal. One-electron oxidation of such compounds results in the formation of unstable radical ions, whose characteristic reactivity patterns include susceptibility to nucleophilic attack, disproportionation, and metal-carbon bond dissociation. Two-electron oxidation may result in dissociation or oxidation of the organic ligand. In this review studies on the chemical and electrochemical oxidations of metal carbonyls, metal-olefin complexes, and alkyl transition-metal compounds are described. The studies encompass the following themes: (1) The kinetics and thermodynamics of the initial redox steps; (2) The characterization and reactivity patterns of the resulting oxidation products; (3) The synthetic and catalytic applications of organometallic redox processes. 相似文献
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Lothar Weber 《Angewandte Chemie (International ed. in English)》1996,35(3):271-288
The chemistry of low-valent organophosphorus compounds such as phosphaalkenes and phosphaalkynes has undergone rapid development in the last two decades. This development also includes the coordination chemistry of these species, which can act as versatile ligands in metal complexes. Metallophosphaalkenes are compounds in which one or more of the organic substituents on the P?C unit is replaced by a transition metal complex fragment. Metallophosphaalkenes have emerged from an existence as laboratory curiosities to become a link between main group and organometallic complex chemistry. The great richness of their chemistry not only mirrors the specific properties of the individual building block, but also shows novel and individual traits. Particular examples are cycloadditions of these electron-rich heteroalkenes with electron-deficient alkenes, alkynes, azo, and diazo compounds. These often lead to novel types of reaction and compounds. Metallophosphaalkenes are also important as intermediates in all metal-assisted cyclooligomerizations of phosphaalkynes. 相似文献
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Wolfgang A. Herrmann 《Angewandte Chemie (International ed. in English)》1978,17(11):800-812
In recent years, aliphatic diazo compounds have proved to be more and more versatile as reagents in the preparative chemistry of organometallic complexes. As readily accessible compounds, they are not only suitable for the synthesis of known kinds of metal complexes but also open fresh routes to novel complex systems. The comparatively new field of diazoalkane complex chemistry exhibits numerous unexpected and novel reactions, and introduces interesting and promising aspects into the chemistry of carbonylmetal compounds. 相似文献
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Reaction of Fc(S)PS2P(S)Fc with NaOEt gives the non symmetric phosphonodithioato anion [Fc(EtO)PS2]‐ which can be complexed to a range of metal ions. The group 10 metals (Ni, Pd and Pt) adopt [ML2] complexes with square planar coordination. The first known mercury phosphonodithioate complex is shown to adopt a unique dimeric [M2L4] structure. A new structural motif for lead phosphonodithioate complexes is reported consisting of [PbL2] units joined by Pb···S interactions to form distinct dimeric pairs. All new compounds have been characterized spectroscopically and four demonstrative X‐ray structures are reported. 相似文献
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P. Natarajan 《Journal of Chemical Sciences》1984,93(6):1003-1014
Transition metal complexes display a number of charge-transfer bands in the absorption spectra. Optical excitation of the
metal complexes produces a variety of products depending upon the nature of the excited state. Cobalt (III) ammine complexes
on excitation in the CTTM bands produce cobalt(II) and oxidised ligand. Ruthenium(II) complexes on excitation in the cm. band
leads to the oxidation of the metal centre. In certain reactions participation of the solvent in the primary photoredox reactions
has also been reported. In recent years extensive investigations have been undertaken to utilize the photoredox systems of
coordination compounds to convert solar energy to electricity or hydrogen. 相似文献
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Silicon-containing flame retardant epoxy resins: Synthesis, characterization and properties 总被引:1,自引:0,他引:1
L.A. Mercado 《Polymer Degradation and Stability》2006,91(11):2588-2594
Epoxy resins with different silicon contents were prepared from silicon-containing epoxides or silicon-containing prepolymers by curing with 4,4′-diaminodiphenylmethane. The reactivity of the silicon-based compounds toward amine curing agents was higher than that of the conventional epoxy resins. The Tg of the resulting thermosets was moderate and decreased when the silicon content increased. The onset decomposition temperatures decreased and the char yields increased when the silicon content increased. Epoxy resins had a high LOI value, according to the efficiency of silicon in improving flame retardance. 相似文献