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31.
Kronenburg CM Jastrzebski JT Boersma J Lutz M Spek AL van Koten G 《Journal of the American Chemical Society》2002,124(39):11675-11683
Reaction of 2 molar equiv of the diamine chelated aryllithium dimers Li(2)(C(6)H(4)[CH(2)N(Et)CH(2)CH(2)NEt(2)]-2)(2) (Li(2)Ar(2)) with the appropriate metal bromide allows the synthesis of the first homologous series of monomeric group 11 bromoate complexes of type MLi(2)BrAr(2) (M = Cu (7), Ag (8), Au (9)). Both in the solid state and in solution, the bromocuprate 7 is isostructural with the bromoargentate 8. The crystal structures of 7 and 8 consist of a MLi(2) core, and each of the two aryl ligands bridges via electron-deficient bonding between the group 11 metal and one Li atom (d(C(ipso)-M) = 1.941(4) (mean) and 2.122(4) (mean) A, for 7 and 8, respectively). The bromine atom exclusively bridges between the two lithium atoms. Each of the ortho-CH(2)N(Et)CH(2)CH(2)NEt(2) moieties is N,N'-chelate bonded to one lithium (d(N-Li) = 2.195(5) and 2.182(0) (mean) A for 7 and 2.154(8) and 2.220(1) (mean) A for 8). Although the MLi(2)BrAr(2) compounds are neutral higher-order -ate species, the structure can also be regarded as consisting of a contact ion pair consisting of two ionic fragments, [Li-Br-Li](+) and [Ar(2)M](-), which are interconnected by both Li-N,N'-chelate bonding and a highly polar C(ipso)-Li interaction. On the basis of NMR and cryoscopic studies, the structural features of the bromoaurate 9 are similar to those of 7 and 8. A multinuclear NMR investigation shows that the bonding between the [Li-Br-Li] and [Ar(2)M] moieties is intermediate between ionic and neutral with an almost equally polarized C(ipso)-Li bond in 7, 8, and 9. Similar reactions between M(C(triple bond)N) and 2 molar equiv of LiAr yield the analogous 2:1 cyanoate complexes of type MLi(2)(C(triple bond)N)Ar(2) (M = Ag (10), Au (11)). Multinuclear NMR studies show that the cyanoate complexes 10 and 11 are isostructural with the bromoate complexes 7, 8, and 9. This paper illustrates that these cyanoaurates may serve as excellent model complexes to gain more insight into the structure of 2:1 cyanocuprates in solution. 相似文献
32.
针对政策可能对金融收益产生风险问题,提出了基于Hilbert-Huang变换方法的政策风险因子识别检测方法。通过经验模态分解,Hilbert-Huang频谱分析得到金融时间序列的时域和频域特征,通过与量化处理后的政策进行匹配得到政策产生的异常波动情况,从而实现对政策因子风险的识别与处理。研究结果对于探究宏观政策对金融收益的影响具有重要参考意义。最后以国家房地产调控政策与地产指数为算例,发现本研究提出的方法识别精度高,具有非常好的应用前景。 相似文献
33.
H.K. Hofstee J. Boersma G.J.M. Van Der Kerk 《Journal of organometallic chemistry》1979,168(2):241-249
The reaction of diarylzinc compounds with silver(I) salts is an excellent method of preparing stable arylsilver compounds in quantitative yields. These compounds have been characterized by IR and 1H and 13C NMR spectroscopy Cryoscopy in benzene shows phenylsilver to be polymeric, and the methyl-substituted phenylsilver compounds to be trimers. All the compounds appear to be associated via aryl groups bridging between two silver atoms. As in the case of the corresponding copper compounds, the data point to the existence of rotation of these aryl groups around the C1C4 axis. C1C4 axis. 相似文献
34.
J. Blenkers H.K. Hofstee J. Boersma G.J.M Van der Kerk 《Journal of organometallic chemistry》1979,168(2):251-258
Diarylsilverlithium compounds of the type Ar2AgLi are formed by treating arylsilver compounds with the corresponding aryllithium compounds. Cryoscopy in benzene shows that the Ar2AgLi compounds are associated into dimers. NMR spectroscopic data indicate that only one type of aryl group is present in these dimers, and that each aryl group is bridging between one silver and one lithium atom. 相似文献
35.
Ahrens J Bai X Barwick SW Becka T Becker JK Bernardini E Bertrand D Binon F Biron A Boersma DJ Böser S Botner O Bouchta A Bouhali O Burgess T Carius S Castermans T Chen A Chirkin D Collin B Conrad J Cooley J Cowen DF Davour A De Clercq C DeYoung T Desiati P Dewulf JP Ekström P Feser T Gaisser TK Ganugapati R Gaug M Geenen H Gerhardt L Goldschmidt A Gross A Hallgren A Halzen F Hanson K Hardtke R Harenberg T Hauschildt T Helbing K Hellwig M Herquet P Hill GC Hubert D Hughey B Hulth PO Hultqvist K 《Physical review letters》2004,92(7):071102
We present the results of a search for point sources of high-energy neutrinos in the northern hemisphere using AMANDA-II data collected in the year 2000. Included are flux limits on several active-galactic-nuclei blazars, microquasars, magnetars, and other candidate neutrino sources. A search for excesses above a random background of cosmic-ray-induced atmospheric neutrinos and misreconstructed downgoing cosmic-ray muons reveals no statistically significant neutrino point sources. We show that AMANDA-II has achieved the sensitivity required to probe known TeV gamma-ray sources such as the blazar Markarian 501 in its 1997 flaring state at a level where neutrino and gamma-ray fluxes are equal. 相似文献
36.
Kleij AW Gossage RA Jastrzebski JT Boersma J van Koten G 《Angewandte Chemie (International ed. in English)》2000,39(1):176-178
Advantages of homo- and heterogeneous catalysts are united in metallodendritic molecules where nickel-based catalysts are bound to carbosilane dendrimers. The first direct indication of a "dendritic effect" in the redox catalysis behavior is described: variation of the dendrimer support controls the proximity of the Ni(II) centers, which in turn controls catalytic activity. Catalyst deactivation, by means of Ni(III) formation, can be avoided by a larger separation of the Ni(II) centers (see picture). 相似文献
37.
The allylic CN bond of CH2CHCH2NEt2 is cleaved by Zn[Co(CO)4]2, producing π-C3H5Co (CO)3. The proparg 相似文献
38.
39.
It is shown that the requirement of a fixed intermediate-range 1S0 proton-proton interaction considerably reduces the model dependence of the Coulomb-corrected p-p scattering length. A possible relation with the off-shell effective range parameter is discussed. 相似文献
40.
Misiejuk A Papandreou Z Voutier E Bauer TS Blok HP Boersma DJ Den Bok HW Bruins EE Farzanpay F Grüner K Hesselink WH Huber GM Jans E Kalantar-Nayestanaki N Kasdorp WJ Konijn J Laget JM Lapikás L Lolos GJ Onderwater GJ Pellegrino A Schroevers R Spaltro CM Starink R van der Steenhoven G Steiger JJ Visschers JL Willering HW Yeomans DM 《Physical review letters》2002,89(17):172501
The differential cross section for electron-induced neutron knockout in the reaction 4He(e,e(')n)(3)He has been measured for the first time with a statistical accuracy of 11%. The experiment was performed in quasielastic kinematics at a momentum transfer of 300 MeV/c and in the missing-momentum range of 25-70 MeV/c. The comparison of the data with theoretical calculations shows an impressive increase of the cross section resulting from final state interaction effects. Specifically, the p-n charge-exchange process dominates the cross section in this kinematical regime. 相似文献