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31.
Dr. Lewis C. H. Maddock Rebekka Morton Dr. Alan R. Kennedy Prof. Dr. Eva Hevia 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(61):15181-15187
Alkali-metal ferrates containing amide groups have emerged as regioselective bases capable of promoting Fe−H exchanges of aromatic substrates. Advancing this area of heterobimetallic chemistry, a new series of sodium ferrates is introduced incorporating the bulky arylsilyl amido ligand N(SiMe3)(Dipp) (Dipp=2,6-iPr2-C6H3). Influenced by the large steric demands imposed by this amide, transamination of [NaFe(HMDS)3] (HMDS=N(SiMe3)2) with an excess of HN(SiMe3)(Dipp) led to the isolation of heteroleptic [Na(HMDS)2Fe{N(SiMe3)Dipp}]∞ ( 1 ) resulting from the exchange of just one HMDS group. An alternative co-complexation approach, combining the homometallic metal amides [NaN(SiMe3)Dipp] and [Fe{N(SiMe3)Dipp}2] induces lateral metallation of one Me arm from the SiMe3 group in the iron amide furnishing tetrameric [NaFe{N(SiCH2Me2)Dipp}{N(SiMe3)Dipp}]4 ( 2 ). Reactivity studies support that this deprotonation is driven by the steric incompatibility of the single metal amides rather than the basic capability of the sodium reagent. Displaying synergistic reactivity, heteroleptic sodium ferrate 1 can selectively promote ferration of pentafluorobenzene using one of its HMDS arms to give heterotrileptic [Na{N(SiMe3)Dipp}(HMDS)Fe(C6F5)]∞ ( 4 ). Attempts to deprotonate less activated pyridine led to the isolation of NaHMDS and heteroleptic Fe(II) amide [(py)Fe{N(SiMe3)Dipp}(HMDS)] ( 5 ), resulting from an alternative redistribution process which is favoured by the Lewis donor ability of this substrate. 相似文献
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Petrus Zwart John Taylor Simon Morton Randall Cayford Gerald Fontenay Marc Allaire 《Synchrotron Radiation News》2015,28(2):22-27
The Berkeley Center for Structural Biology (BCSB) operates and develops a suite of protein crystallography beamlines at the Advanced Light Source (ALS) located at Lawrence Berkeley National Laboratory (LBNL). Although the ALS was conceived as a low-energy (1.9-GeV), third-generation synchrotron source of vacuum ultraviolet (VUV) and soft X-ray radiation, it was realized during the development of the facility in the mid-1990s that a multipole wiggler coupled with brightness-preserving optics would result in a beamline whose performance in the energy range of 5 to 15 keV would be sufficient for most protein crystallographic experiments. Later, the hard X-ray capabilities of the ALS were expanded by the addition of three superconducting bending magnets, resulting in additional protein crystallography facilities at the ALS [1]. 相似文献
33.
Solène Béchu Muriel Bouttemy Jackie Vigneron Daniel Lincot Jean-François Guillemoles Arnaud Etcheberry 《Surface and interface analysis : SIA》2020,52(12):975-979
Cu(In,Ga)Se2 absorbers were immerged in deionized water for different times, and specific chemical evolutions were monitored thanks to X-ray photoemission spectroscopy. Cu(In,Ga)Se2 related dissolution products were studied in water through induced coupled plasma optical emission spectroscopy. From those analyses, specific surface network disorganization was observed, with Cu migration towards the surface, leading to different kinetics of oxidation and dissolution for each element that could be quantified. 相似文献
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The methyl cation and CF(3)(+) attack saturated, acyclic ketones to make vibrationally excited adduct ions. Despite their high internal energies and short lifetimes, these adducts undergo deep-seated rearrangements that parallel slower processes in solution. Observed pathways include alkene and alkane expulsions, in addition to (in the case of CF(3)(+)) the precedented loss of CF(2)O + HF. For the vast majority of ketones, the principal charged products are the CF(3)(+) adducts of lighter carbonyl compounds, ions that are not easily prepared by other avenues. Evidence for ion structures comes from collisionally activated unimolecular decomposition and bimolecular ion-molecule reactions. Typical examples are di-n-propyl and diisopropyl ketones (both of which produce CH(3)CH=OCF(3)(+) as the principal ion-molecule reaction product) and pentamethylacetone (which produces (CH(3))(2)C=OCF(3)(+) as virtually the sole ion-molecule reaction product). Isotopic labeling experiments account for mechanisms, and DFT calculations provide a qualitative explanation for the relative abundances of products from unimolecular decompositions of the chemically activated CF(3)(+) adduct ions that are initially formed. 相似文献
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Multistage stochastic programs with interstage independent random parameters have recourse functions that do not depend on
the state of the system. Decomposition-based algorithms can exploit this structure by sharing cuts (outer-linearizations of
the recourse function) among different scenario subproblems at the same stage. The ability to share cuts is necessary in practical
implementations of algorithms that incorporate Monte Carlo sampling within the decomposition scheme. In this paper, we provide
methodology for sharing cuts in decomposition algorithms for stochastic programs that satisfy certain interstage dependency
models. These techniques enable sampling-based algorithms to handle a richer class of multistage problems, and may also be
used to accelerate the convergence of exact decomposition algorithms.
Research leading to this work was partially supported by the Department of Energy Contract DE-FG03-92ER25116-A002; the Office
of Naval Research Contract N00014-89-J-1659; the National Science Foundation Grants ECS-8906260, DMS-8913089; and the Electric
Power Research Institute Contract RP 8010-09, CSA-4O05335.
This author's work was supported in part by the National Research Council under a Research Associateship at the Naval Postgraduate
School, Monterey, California. 相似文献
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