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One of the most challenging transformations in current organic chemistry is the catalytic carboxylation of a C(sp(3))-H bond using CO(2) gas, an inexpensive and ubiquitous C1 source. A sequential protocol for C(sp(3))-H carboxylation by employing a nitrogen-directed, metal-assisted, C-H activation/catalytic silylation reaction in conjunction with fluoride-mediated carboxylation with CO(2) was established. The carboxylation proceeded only at the benzylic C(sp(3))-Si bond, not at the aromatic C(sp(2))-Si, which is advantageous for further manipulations of the products. 相似文献
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采用1,6-二氯十二甲基六硅烷与对溴苯甲醚的格氏试剂反应制得了标题化合物。对其进行了结构分析。X射线衍射分析表明,该晶体属单斜晶系,分子是中心对称的,化合物呈交叉锯齿型稳定构象。 相似文献
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An efficient process involving Pd-catalyzed selective cleavage of a C(sp(3))-Si bond and consequent intramolecular C(sp(2))-Si coupling has been developed, affording benzosilolo[2,3-b]indoles as a new type of silicon-bridged polyheteroarene in excellent yields. Aldehyde was found for the first time to be able to promote the efficiency of the catalytic process remarkably. 相似文献
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1,1-Disubstituted 3-aryl-2-propyn-1-ols undergo regio- and stereoselective cross-coupling on treatment with bis(trimethylsilyl)acetylene in the presence of a rhodium catalyst via cleavage of C(sp)-C(sp3) and C(sp)-Si bonds to produce the corresponding 2-hydroxymethyl-(E)-enynes. The subsequent desilylative Sonogashira coupling followed by base-promoted cyclization affords fluorescent dihydrofuran derivatives. 相似文献
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基于量子化学ONIOM [B3LYP/6-31G(d,p):UFF]计算方法,研究了β分子筛中BrΦnsted酸的落位及其酸性强度.计算采用22T簇模型,得到了不同酸性位的(Al,H)/Si替代能和质子亲和势.研究结果表明,BrΦnsted酸最有可能落位在Al(8)-O(11).Si(4),Al(8)-O(4)-Si(1),Al(7)-O(7)-Si(2)和Al(9)-O(6)-Si(3)位置.根据去质化能的计算,Al(7)-O(7)-Si(2)位置的酸性最强,A1(8)-O(11)-Si(4)的酸性最弱.酸性的强弱顺序为Al(7)-O(7)-Si(2)>Al(9)-O(6)-Si(3)>Al(8)-0(4)-Si(1)>Al(8)-O(11)-Si(4). 相似文献
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The matching of ring and cap orbitals for overlap is used to arrive at the best carborynes among the many possibilities. Accordingly, 1,2-carboranes, 1,2-silaboranes (C2BnHn+2, and Si2BnHn+2, n = 4, 5, 8, and 10), and their dehydrogeno derivatives were studied with use of the Density Functional Theory (B3LYP/6-311+G*). The dehydrogenation of 2,3-C2B5H7 (6a) to 2,3-C2B5H5 (13a) is estimated to be even less endothermic than those of benzene and 1,2- C2B10H12 (1a) to benzyne and 1,2-C2B10H10 (8a) by more than 21 kcal/mol. This is due to the extra stabilization gained through better overlap of the C2B3H3 ring with the 2 BH caps. The relatively larger size of the Si atom leads to overlap requirements in silaboranes that are different from those in carboranes. The lower Si-Si single bond energy and the preference of Si for lower coordination result in unusual structures in dehydrogenosilaboranes. One of the Si atoms moves away from the surface in Si2B10H10 (15), Si2B8H8 (16, 17, and 18), and 1,2-Si2B5H5 (19). One Si atom forms a bridge to a trigonal surface in 2,3-Si2B5H5 (20) and 1,2-Si2B4H4 (21). Estimates of three-dimensional aromaticity with NICS calculations show that the exohedral double bond does not influence three-dimensional aromaticity. 相似文献
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基于量子化学ONIOM [B3LYP/6-31G(d,p):UFF]计算方法, 研究了β分子筛中Brønsted酸的落位及其酸性强度. 计算采用22T簇模型, 得到了不同酸性位的(Al, H)/Si替代能和质子亲和势. 研究结果表明, Brønsted酸最有可能落位在Al(8)-O(11)-Si(4), Al(8)-O(4)-Si(1), Al(7)-O(7)-Si(2)和Al(9)-O(6)-Si(3)位置. 根据去质化能的计算, Al(7)-O(7)-Si(2)位置的酸性最强, Al(8)-O(11)-Si(4)的酸性最弱. 酸性的强弱顺序为Al(7)-O(7)-Si(2)>Al(9)-O(6)-Si(3)>Al(8)-O(4)-Si(1)>Al(8)-O(11)-Si(4). 相似文献
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M. G. Voronkov S. V. Basenko S. M. Nozdrya V. Yu. Vitkovskii R. G. Mirskov 《Russian Chemical Bulletin》1990,39(7):1507-1509
A study was carried out on the reaction of 1,1,3,3-tetramethyldisiloxane with metal oxides such as CuO, HgO, and Sb2O5 in the presence of compounds containing a siloxane bond such as hexamethyldisiloxane, octamethylcyclotetrasiloxane, and trimethylacetoxysilane, which, at 100–110°C over 0.5–10 h, leads to the formation of linear organyl siloxanes (CH3-[-Si(CH3)2O-]n-Si(CH3)3, CH3-[-Si(CH3)2O-]n-Si (CH3)2H, and H-[-Si(CH3)2O-]n-Si(CH3)2H, where n=2–6, and cyclic organylsiloxanes. The reaction does not proceed in the presence of aluminum, bismuth, germanium, and lead oxides.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1658–1660, July, 1990. 相似文献
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Three cis-3,4-bis(organosilyl)cyclobutenes were synthesized, and their thermal ring-opening reactions were studied. The ring-opening reaction of cis-3,4-bis(trimethylsilyl)cyclobutene proceeded remarkably faster than that of cis-3,4-dimethylcyclobutene. The significant rate acceleration was explained by assuming (i) stabilization of the transition state by electron delocalization from the cyclobutene HOMO to the Si-CH3 sigma* orbital, (ii) destabilization of the ground state by intramolecular interaction between the C-Si sigma orbitals and the pi orbital of cyclobutene, and (iii) through-space steric repulsion of the two bulky trimethylsilyl groups in a cis arrangement. The ring-opening reaction of unsymmetrical cis-3,4-bis(arylsilyl)cyclobutenes having electronically different arylsilyl groups was also examined. The inward preference increased in the order, p-CH3OC6H4-Si, C6H5-Si, p-CF3C6H4-Si, supporting the interpretation of the origin of the inward preference of silyl substituents on the basis of a stabilizing interaction between the cyclobutene HOMO and the Si-C sigma* orbital at the transition state. 相似文献
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基于密度泛函理论,本文提出了一种新的硅同素异形体(C2-Si).根据弹性常数和声子谱研究了C2-Si的力学稳定性和动力学稳定性.根据体积模量与剪切模量的比值,表明了C2-Si在环境压力下具有延展性;与Si64、Si96、I4/mmm和h-Si6相比,C2-Si的脆性较小.在Heyd-Scuseria-Ernzerhof杂化函数中,C2-Si是一种间接窄带隙半导体,C2-Si的带隙仅为0.716 eV,约为c-Si的三分之二.通过C2-Si的杨氏模量、剪切模量和泊松比三维空间分布中的最大值和最小值之比来表征其各向异性.此外,通过不同晶面的杨氏模量、剪切模量和泊松比的二维图分析不同晶面的各向异性.在十多种硅同素异形体中,C2-Si对可见光的吸收能力最强. 相似文献
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Balazs G Cloke FG Harrison A Hitchcock PB Green J Summerscales OT 《Chemical communications (Cambridge, England)》2007,(8):873-875
Structural, magnetic and theoretical studies show that the bimetallic pentalene complex, Mn(2)(C(8)H(4)(1,4-Si(i)Pr(3)))(2), contains both high and low spin Mn(ii) in two very different sites. 相似文献
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合成了2个(CH3(C6H4)N2(C6H3A)COO(C6H4)OCH2-Si(CH3)2)2O化合物,其中A = H为1,A = CH3为2。经IR、1H NMR和元素分析表征,并用2D NMR1H-1H COSY记录了2个化合物中不同取代基苯环上所有质子的化学位移和相关-自旋偶合常数,对谱线的归属作了指认。通过偏光显微镜和DSC分析,1具有液晶性能,而2没有液晶性能。同时,用AM1方法计算了它们的电子结构,讨论了它们的结构与性能之间的关系。 相似文献
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K. Çinar Ş. Aydoğan C. Coşkun 《Journal of Radioanalytical and Nuclear Chemistry》2014,300(3):1113-1120
We deposited GaTe thin films with electrochemical growth technique on p-Si (100) substrate and investigated their structural and electrical properties. The electrical characteristics of the Ti/GaTe/p-Si/Al Schottky diode (SD) were determined by means of I–V (current–voltage) and C–V (capacitance–voltage) measurements. The diodes were irradiated with high energy (18 MeV) and low doses (1.38 × 1010 e? cm?2) electrons. The ideality factor values for Ti/GaTe/p-Si/Al structure were calculated as 1.27 and 1.53 and the barrier heights have been obtained as 0.739 and 0.706 eV from I–V measurements before and after each electron irradiations, respectively. Also, the parameters such as built-in potential, Fermi levels, acceptor concentration and barrier height of the Ti/GaTe/p-Si/Al SD have been calculated by the help of C–V measurements before and after each irradiations. The change in parameters was interpreted by the defect formation at the interface due to the electron irradiation. 相似文献
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Density functional theory (DFT) B3LYP method is used to theoretically investigate the adsorption conformations of H2O and glycol on the relaxation surface of β-Si3N4(0001) with cluster models. For H2O, the most stable structure is that adsorbed through the H atom lying above a N(3) site of the relaxation surface of β-Si3N4(0001); while for glycol, it is the one adsorbed via the H atom lying above the center of Si(2) and N(3) of the same relaxation surface. The adsorption energy, adsorption bond and transfer electrons of the two adsorbed substances prove that glycol is easy to be adsorbed on the relaxation surface of β-Si3N4(0001). 相似文献
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Density functional theory (DFT) B3LYP method is used to theoretically investigate the adsorption conformations of H2O and glycol on the relaxation surface of β-Si3N4(0001) with cluster models. For H2O, the most stable structure is that adsorbed through the H atom lying above a N(3) site of the relaxation surface of β-Si3N4(0001); while for glycol, it is the one adsorbed via the H atom lying above the center of Si(2) and N(3) of the same relaxation surface. The adsorption energy, adsorption bond and transfer electrons of the two adsorbed substances prove that glycol is easy to be adsorbed on the relaxation surface of β-Si3N4(0001). 相似文献
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Dr. Jing-Xin Jian Jia-Xin Liao Mu-Han Zhou Ming-Ming Yao Yi-Jing Chen Xi-Wen Liang Dr. Chao-Ping Liu Prof. Dr. Qing-Xiao Tong 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(57):e202201520
Since the water oxidation half-reaction requires the transfer of multi-electrons and the formation of O−O bond, it's crucial to investigate the catalytic behaviours of semiconductor photoanodes. In this work, a bio-inspired copper-bipyridine catalyst of Cu(dcbpy) is decorated on the nanoporous Si photoanode (black Si, b-Si). Under AM1.5G illumination, the b-Si/Cu(dcbpy) photoanode exhibits a high photocurrent density of 6.31 mA cm−2 at 1.5 VRHE at pH 11.0, which is dramatically improved from the b-Si photoanode (1.03 mA cm−2) and f-Si photoanode (0.0087 mA cm−2). Mechanism studies demonstrate that b-Si/Cu(dcbpy) has improved light-harvesting, interfacial charge-transfer, and surface area for water splitting. More interestingly, b-Si/Cu(dcbpy) exhibits a pH-dependent water oxidation behaviour with a minimum Tafel slope of 241 mV/dec and the lowest overpotential of 0.19 V at pH 11.0, which is due to the monomer/dimer equilibrium of copper catalyst. At pH ∼11, the formation of dimeric hydroxyl-complex could form O−O bond through a redox isomerization (RI) mechanism, which decreases the required potential for water oxidation. This in-depth understanding of pH-dependent water oxidation catalyst brings insights into the design of dimer water oxidation catalysts and efficient photoanodes for solar energy conversion. 相似文献