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1.
Quantum chemical calculations using gradient-corrected density functional theory (B3LYP) and ab initio methods at the MP2
level are reported for the geometries and bond energies of the nitrido complexes Cl2 (PH3)3ReN–X (X = BH3, BCl3, BBr3, AlH3, AlCl3, AlBr3, GaH3, GaCl3, GaBr3, O, S, Se, Te). The theoretical geometries are in excellent agreement with experimental values of related complexes which
have larger phosphine ligands. The parent nitrido complex Cl2(PH3)3ReN is a very strong Lewis base. The calculated bond dissociation energy of Cl2(PH3)3ReN–AlCl3 is D
e = 43.7 kcal/mol, which is nearly as high as the bond energy of Me3N–AlCl3. The donor-acceptor bonds of the other Cl2(PH3)3ReN–AY3 complexes are also very strong. Even stronger N–X bonds are predicted for most of the nitrido-chalcogen complexes, which
exhibit the trend X = O ≫ S > Se > Te. Analysis of the electronic structure shows that the parent compound Cl2(PH3)3ReN has a Re–N triple bond. The Re–N σ bond is clearly polarized towards nitrogen, while the two π bonds are nearly nonpolar.
The Re–N σ and π bonds become more polarized toward nitrogen when a Lewis acid or a chalcogen atom is attached. Bonding in
AY3 complexes should be described as Cl2(PH3)3ReE≡N→AY3, while the chalcogen complexes should be written with double bonds Cl2(PH3)3Re=N=X. The charge-decomposition analysis indicates that the nitrogen-chalcogen bonds of the heavier chalcogen complexes with
X = S, Se, Te can also be interpreted as donor-acceptor bonds between the nitrido complex acting as a Lewis base and the chalcogen
atom with an empty p(σ) orbital acting as a Lewis acid. The nitrido oxo complex Cl2(PH3)3 Re=N=O has a covalent N–O double bond.
Received: 27 July 1998 / Accepted: 26 October 1998 / Published online: 16 March 1999 相似文献
2.
The hydrosilylation reaction of ladderlike polyvinylsilsesquioxane (Vi-T)with 1, 1, 3, 3-tetramethyldisiloxane (H- MM ) catalyzed by dicyclopentadienyl-dichloroplat-inium (Cp_2PtCl_2) was carried out well in tetrahydrofuran (THF) to produce a soluble whitesolid. This product was characterized by IR, ~1H-NMR, ~(13)C-NMR, ~(29)Si-NMR, DSC, X-raydiffraction method, gel permeation chromatography (GPC), vapour pressure osmometry(VPO), atomic force microscopy (AFM) and molecular simulation. These results provethat the product contains nanoscale tubular structure. 相似文献
3.
Synthesis of 3-Phenyl-6-formyl-3, 4-dihydro-2H-1, 3-benzoxazine 总被引:2,自引:0,他引:2
Qi Chao RAN Qiao TIAN Yi GU 《中国化学快报》2006,17(10):1305-1308
Benzoxazine is a novel class of thermosetting resins, which possesses lots of outstanding properties such as no by-products and near-zero shrinkage during polymerization as well as good molecular design flexibility1-2. Furthermore, polybenzoxazines (PBZs)… 相似文献
4.
TaiXIAO HuiXueLI ChunXiaTAN MiaoCHEN 《中国化学快报》2005,16(3):335-337
A series of 3-pyridinyl-6-aryl-1, 2, 4-triazolo[3, 4-b][1, 3, 4]thiadiazoles(PATT) were prepared, the structures were confirmed by 1R and ^1H NMR spectra. The results of cyclic voltammetry measurements imply that all these compounds have a higher electron affinity (EA) than 2-(4-biphenyl)-5-(4-tert-butyl phenyl)-1, 3. 4-oxadiazole (PBD) which implies that PATT could be acting as better electron acceptors than widely used electron transporting material PBD. 相似文献
5.
Christopher W. Tate Peter B. Hitchcock Gerard A. Lawless Zoltán Benkő László Nyulászi John F. Nixon 《Comptes Rendus Chimie》2010,13(8-9):1063-1072
The molecular structure of the previously reported compound [Mo(CO)3(η6-P3C3But3)] has been determined by a single-crystal X-ray diffraction study. Syntheses and molecular structures are also described for the structurally related compounds [Mo(CO)3(η5-P3C3But3)(Me)(Bun)], [Mo(CO)3(η5-P3C3But3)(H)(Bun)] and [Mo(CO)3(η4-P3C3But3(Me)(Bun)(H)(O)Li(THF)3]. Density functional calculations at the B3LYP/cc-pVDZ(-PP) and BP86/cc-pVDZ(-PP) levels have been carried out on the above complexes and the nature of the bonding between the different rings and molybdenum is discussed. 31P NMR spectroscopic evidence is presented for the existence of the novel complex [Mo(CO)3(η6-P3C3But3)PtCl2(PEt3)] in which the triphosphabenzene ring acts as an overall 8-electron donor to the two metal centres. 相似文献
6.
BiflavonesareamorecomPlicatedclass0fflavonoids.MostofthemareusefulcomPonentsoftraditionalmedicinetocurediseases.Sincechamaejasminel,anewtoeofbiflavonoidpossessingaC-3/C-3"linkage,wasisolatedfromSteUerachamaejasmaeL.byHuangetal',especiallyafterthebiologicalactivityofani-cancerwasdiscovered',thestUdyof3,3"-biflavonoidshasattfactCdmuchattention.3-5ButtherehasbeennoprogressmentionedonthesynthesisofthiskindofcomPoundsinrecentdecades.AsaresultofoursystematicresearchonthesynthesisofchamaejasInin… 相似文献
7.
A. V. Mal’tseva T. V. Gubanova I. K. Garkushin 《Russian Journal of Inorganic Chemistry》2013,58(2):219-223
Phase equilibria in Li,K∥F,NO3 and Li,K∥Cl,NO3 three-component reciprocal systems were studied by differential scanning calorimetry (DSC). Eutectic compositions (mol %) in the Li,K∥F,NO3 system were determined to be as follows: 5.0 LiF, 10.0 KF, and 85.0 KNO3 with T m = 281°C and 48.5 KNO3, 44.0 LiNO3, and 7.5 LiF with T m = 105°C. Eutectic compositions (mol %) in the Li,K∥Cl,NO3 system were determined to be as follows: 10.0 LiCl, 32.1 KCl, and 57.9 LiNO3 with T m = 147°C and 44.5 KNO3, 45.0 LiNO3, and 10.5 KCl with T m = 97°C. 相似文献
8.
Dr. Ze-Jun Xu Yan Zong Ya-Nan Qiao Jiao-Zhen Zhang Xuyuan Liu Ming-Zhu Zhu Yuliang Xu Hongbo Zheng Liyuan Fang Dr. Xiao-ning Wang Prof. Hong-Xiang Lou 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(45):20091-20095
A divergent synthetic approach to biogenetically related diterpenoids such as ent-kauranes, ent-trachylobanes, ent-beyerane, and ent-atisane has been developed. The unified synthetic route involves the De Mayo reaction to rapidly generate the bicyclo[3.2.1]-octane moiety of ent-kaurane. The key reactions also include bioinspired nucleophilic cyclopropanation generating the [3.2.1.02,7]-tricyclic core of ent-trachylobane and regioselective cyclopropane fragmentation furnishing ent-beyerane and ent-atisane through the nucleophilic attack and protonation of the cyclopropane ring. This strategy enables the asymmetric total syntheses of six diterpenoids from the commercially available geraniol. 相似文献
9.
We have shown that some phenylethynylsilicon compounds are good cure crosslinkersof heat-curable silicone rubber(HCSR). In this paper the effects of 1, 1, 3, 3-tetramethyl-1, 3-diphenylethynyldisiloxane (TMDPDS) as a crosslinker on HCSR were studied. Thevulcanizates with fine mechanical properties could be obtained with suitable amounts ofTMDPDS. Sol fractions, and crosslinking density of vulcanizates and vulcanizationretardation effect of TMDPDS on hydrosilation curing silicone rubber were also discussed. 相似文献
10.
《Analytical letters》2012,45(3)
Abstract This is a scanned image of the original Editorial Board page(s) for this issue. 相似文献
11.
《中国化学快报》1997,(2)
HormoneisaveryhoP0tatkindofbiol0glcalmolede,ltplaTharegulationro1einmetabelism.TheinterachoLofrareeothwithborm0nehasearelybeenreporteds0far[1'2J.lntheprerentwork,theinteraedonofrareearthwith3.5,3'-triiodothryor`ire(T.)wasstodiaibyusingNMRandPOtentiometrictitrationat37tandanionicstrenotofO'15mo1e/LNaC1,TheP0tenhometrictitrah0nwasperformedin1:1DMSO-H.O(vol1imeratio)usingthemethoddedndinprevi01ispeper[3].TheNMR8peaofsarnples(PH=4,to)wererecorded'onBrukerARX-4ooNMRSpeCtrometerusingT… 相似文献
12.
A new monomer, 3,9-diallyl-3, 9-dibenzyl-1, 5,7,11 - tetraoxa- spiro [5,5] undecane (6) was prepared by the reaction of 2- allyl- 2' - benzyl- propanediol - 1.3 with dibutyltin oxide, and then treated with CS_2. Monomer 4 could be initiated by cationic initiators to give a viscous polymer (white powder in the case of polymerization at 0℃). Upon the NMR and IR spectra of the obtained polymer, the components and their relative amount were estimated. The polymerization mechanism was discussed. 相似文献
13.
《Tetrahedron letters》1988,29(36):4535-4538
The title compounds are described for the first time and are the result of (3+2)- and (4+2)-cycloaddition reactions with phosphaalkenes. 相似文献
14.
硼酸盐玻璃中Gd^3+,Dy^3+,Bi^3+对Tb^3+发光性质的影响 总被引:1,自引:0,他引:1
本文研究了单掺和双掺(Tb~(3+)、Tb~(3+)+Gd~(3+)、Tb~(3+)+Dy~(3+)、Tb~(3+)+Bi~(3+)约四十余种不同成份的硼酸盐玻璃。探讨了玻璃成份对Tb~(3+)发光性质的影响和Gd~(3+)、Dy~(3+)、Bj~(3+)对Tb~(3+)的胜化作用。在B_2O_2-BaO-M_mO_n(M_mO_n=Li_2O、Na_2O、K_2O、MgO、CaO、SrO、Al_2O_3、La_2O_3和Bi_2O_3)玻璃体系中,当M_mO_n分别为MgO和Al_2O_3时,Tb~(3+)的发光强度最强;M_mO-n为Bi_2O_3时,Tb~(3+)的发光强度最弱。Tb~(3+)的特征发射峰分别随着碱金属、碱土金属和三价金属的离子半径增加而红移。Gd~(3+)、Dy~(3+)、Bi~(3+)对Tb~(3+)均有敏化作用。特别是Gd~(3+),使Tb~(3+)的发光强度增加1~3.8倍,其最佳敏化浓度,因基质玻璃成份而异。 相似文献
15.
高效液相色谱法同时测定食品中脂溶性维生素A,D3,E,K3 总被引:3,自引:0,他引:3
1引言维生素是维持细胞正常生理功能的营养成分之一。许多维生素是酶的辅基或酶的组成成分,因此,测定食品中维生素的含量是食品营养分析的主要内容之一。脂溶性维生素的分析方法一般采用生物法、分光光度法及薄层色谱法等,但这些方法都只能单独测定食品中的维生素,进入80年代后,随着高效液相色谱(HPLC)技术在食品分析中的应用,国外许多研究工作者在利用高效液相色谱技术分析脂溶性维生素的研究上作了许多工作,发展了更具选择性的方法如电化学法、质谱法等,并且对同时测定脂溶性维生素的方法作了一些探索。本文旨在综合国内… 相似文献
16.
《结构化学》1992,(2)
<正> The structure of title compound [C7H6N2OPS3]-·[HNC5H5]+ was determined by x-ray diffraction. It belongs to monoclinic system with space group P21/a, a = 16.745(2), b= 8.563(2), c=21. 050(5)(?), β=93.32(1)°, V= 3013. 6(?)3, Z = 8, Mr = 341. 4, F (000) = 1536, Dc=1. 504 g. cm-3,μ= 53. 0 cm-1. The crystal is composed of discrete cations C5H5NH+ and anions CrH6N2OPS3-. There are two pairs of the cations and the anions in each asymmetric unit. The stability of the anion is increased by the formation of (d-p)π bonding involving the 3d orbital of the P atom and the lone electron pairs of the S atoms. 相似文献
17.
在教电子构型一节时,学生们往往感到难于记住轨道的填充次序,许多教科书(也有不少教师)对此也没有给出有效的解决办法。本文介绍一个简便实用的方法,将有助于对这一问题的学习和记忆。做法如下: 1.画一张7×7的方格子图。2.在对角线上算出已知的各S轨道。 相似文献
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20.
S. Madan Kumar 《合成通讯》2013,43(5):793-802
The nucleophilic substitution of the nitro group in 5-nitrobenzofurazan-3-oxide is studied undder soild-liquid phase-transfer catalysis (PTC) conditions. 相似文献