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Sinnema PJ Shapiro PJ Foo DM Twamley B 《Journal of the American Chemical Society》2002,124(37):10996-10997
Ring borylation of [Me4C2(eta5-C5H4)2CrCO] by B(C6F5)3 affords the zwitterionic complex {Me4(eta5-C5H4)(eta5-C4H3B(C6F5)3)}CrH(CO) (1), the first structurally characterized bent-metallocene complex of Cr(4+). This species decomposes thermally to the zwitterionic species {Me4(eta5-C5H4)(eta5-C4H3B(C6F5)3)}Cr (2) and the ionic species [Me4C2(eta5-C5H4)2CrCO][HB(C6F5)3] (3). The molecular structure of 2 is also described. 相似文献
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Addition of isonicotinic acid NC(5)H(4)CO(2)H (or isonicH) to [Pt(dppf)(MeCN)(2)](2+)2OTf(-)(dppf = 1,1'-bis(diphenylphosphino)ferrocene, OTf = triflate) affords a mixture of the homometallic molecular square [Pt(4)(dppf)(4)(mu-O(2)CC(5)H(4)N)(4)](4+)4OTf(-), 1 and its precursor intermediate [Pt(dppf)(eta(1)-NC(5)H(4)CO(2)H)(2)](2+)2OTf(-), 2. The latter captures [Pd(dppf)(MeCN)(2)](2+)2OTf(-) to give a heterometallic square, [Pt(2)Pd(2)(dppf)(4)(mu-O(2)CC(5)H(4)N)(4)](4+)4OTf(-), 3. Slight skeletal modification of the ligand leads to different assemblies. This is illustrated by the addition of NC(5)H(4)CH(2)CO(2)H.HCl to [Pt(dppf)(MeCN)(2)](2+)2OTf(-) to give [PtCl(dppf)(NC(5)H(4)CH(2)CO(2)H)](+)OTf(-), 4, which reacts with another equivalent of AgOTf to yield the dibridged complex [Pt(2)(dppf)(2)(mu-NC(5)H(4)CH(2)CO(2))(2)](2+)2OTf(-), 5. All complexes, with the exception of , have been structurally characterized by single-crystal X-ray crystallography. Complexes 2 and 4 are potential precursors to further molecular topologies. 相似文献
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Fabrizio Innocenti Dr. Marie Eypper Edmond P. F. Lee Dr. Stefano Stranges Dr. Daniel K. W. Mok Dr. Foo‐tim Chau Prof. George C. King Prof. John M. Dyke Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(36):11452-11460
The first photoelectron band of difluorocarbene CF2, has been studied by threshold photoelectron (TPE) spectroscopy. CF2 was prepared by microwave discharge of a flowing mixture of hexafluoropropene, C3F6, and argon. A vibrationally resolved band was observed in which at least twenty‐two components were observed. In the first PE band of CF2, the adiabatic ionization energy differs significantly from the vertical ionization energy because, for the ionization CF2+ (X?2A1)+e? ← CF2 (X?1A1), there is an increase in the FCF bond angle (by ≈20°) and a decrease in the C? F bond length (by ≈0.7 Å). The adiabatic component was not observed in the experimental TPE spectrum. However, on comparing this spectrum with an ab initio/Franck–Condon simulation of this band, using results from high‐level ab initio calculations, the structure associated with the vibrational components could be assigned. This led to alignment of the experimental TPE spectrum and the computed Franck–Condon envelope, and a determination of the first adiabatic ionization energy of CF2 as (11.362±0.005) eV. From the assignment of the vibrational structure, values were obtained for the harmonic and fundamental frequencies of the symmetric stretching mode (ν1′) and symmetric bending mode (ν2′) in CF2+ (X?2A1). 相似文献
45.
Dr. Tianyi Chen Christopher Foo Dr. Jianwei J. W. Zheng Huihuang Fang Prof. Peter Nellist Prof. Shik Chi Edman Tsang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(47):12041-12046
It has only recently been established that doping light elements (lithium, boron, and carbon) into supported transition metals can fill interstitial sites, which can be observed by the expanded unit cell. As an example, interstitial lithium (intLi) can block H filling octahedral interstices of palladium metal lattice, which improves partial hydrogenation of alkynes to alkenes under hydrogen. In contrast, herein, we report intLi is not found in the case of Pt/C. Instead, we observe for the first time a direct ‘substitution’ of Pt with substitutional lithium (subLi) in alternating atomic columns using scanning transmission electron microscopy-annular dark field (STEM-ADF). This ordered substitutional doping results in a contraction of the unit cell as shown by high-quality synchrotron X-ray diffraction (SXRD). The electron donation of d-band of Pt without higher orbital hybridizations by subLi offers an alternative way for ultra-selectivity in catalytic hydrogenation of carbonyl compounds by suppressing the facile CO bond breakage that would form alcohols. 相似文献
46.
平胃散挥发性成分的研究(Ⅱ)--厚朴挥发油的GC/MS分析 总被引:3,自引:0,他引:3
利用色质联用(GC/MS)技术对复方制剂平胃散中的单味药材厚朴的挥发油成分进行测定,基于直观推导式演进特征投影(HELP)法对产生的二维色谱/质谱数据进行分辨,得到各个组分的纯色谱曲线和质谱,根据色谱保留时间和纯质谱在质谱库中进行相似检索以实现对组分的定性,然后采用总休整积分法进行定量,本文分离出98个组分,其中鉴定了44个组分,约占其挥发油总量的58.74%。 相似文献
47.
Sie Tiong Ha Lay Khoon Ong Siew Ling Lee Hong Cheu Lin Yip Foo Win Siew Teng Ong 《中国化学快报》2010,21(6):637-640
<正>A homologous series of Schiff base esters,4-chlorobenzylidene-4'-n-alkanoyloxyanilines,containing even number of carbons at the end groups of the molecules(C_(n-1)H_(2n-1)COO-,n=4,6,8,10,12,14,16) were synthesized.The mesomorphic properties were investigated by differential scanning calorimetry(DSC) and polarizing optical microscopy(POM).It was found that the end groups of the molecules had an effect on the mesomorphic properties.n-Butanoyloxy was found non-mesogenic,whilst n-hexanoyloxy exhibited monotropic smectic phase.The higher members in this homologous series were enantiotropic smectogens. 相似文献
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We consider a large declining population of cells under an external selection pressure, modeled as a subcritical branching process. This population has genetic variation introduced at a low rate which leads to the production of exponentially expanding mutant populations, enabling population escape from extinction. Here we consider two possible settings for the effects of the mutation: Case (I) a deterministic mutational fitness advance and Case (II) a random mutational fitness advance. We first establish a functional central limit theorem for the renormalized and sped up version of the mutant cell process. We establish that in Case (I) the limiting process is a trivial constant stochastic process, while in Case (II) the limit process is a continuous Gaussian process for which we identify the covariance kernel. Lastly we apply the functional central limit theorem and some other auxiliary results to establish a central limit theorem (in the large initial population limit) of the first time at which the mutant cell population dominates the population. We find that the limiting distribution is Gaussian in both Cases (I) and (II), but a logarithmic correction is needed in the scaling for Case (II). This problem is motivated by the question of optimal timing for switching therapies to effectively control drug resistance in biomedical applications. 相似文献