- Models for the active site in [FeFe] hydrogenase with iron-bound ligands derived from Bis-, Tris-, and tetrakis(mercaptomethyl)silanes
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A series of multifunctional (mercaptomethyl)silanes of the general formula type RnSi(CH2SH)4-n (n = 0-2; R = organyl) was synthesized, starting from the corresponding (chloromethyl)silanes. They were used as multidentate ligands for the conversion of dodecacarbonyltriiron, Fe3(CO)12, into iron carbonyl complexes in which the deprotonated (mercaptomethyl)silanes act as μ-bridging ligands. These complexes can be regarded as models for the [FeFe] hydrogenase. They were characterized by elemental analyses (C, H, S), NMR spectroscopic studies ( 1H, 13C, 29Si), and single-crystal X-ray diffraction. Their electrochemical properties were investigated by cyclic voltammetry to disclose a new mechanism for the formation of dihydrogen catalyzed by these compounds, whereby one sulfur atom was protonated in the catalytic cycle. The reaction of the tridentate ligand MeSi(CH 2SH)3 with Fe3(CO)12 yielded a tetranuclear cluster compound. A detailed investigation by X-ray diffraction, electrochemical, Raman, Moessbauer, and susceptibility techniques indicates that for this compound initially [Fe2{μ-MeSi(CH2S) 2CH2SH}(CO)6] is formed. This dinuclear complex, however, is slowly transformed into the tetranuclear species [Fe 4{μ-MeSi(CH2S)3}2(CO) 8].
- Apfel, Ulf-Peter,Troegel, Dennis,Halpin, Yvonne,Tschierlei, Stefanie,Uhlemann, Ute,Goerls, Helmar,Schmitt, Michael,Popp, Juergen,Dunne, Peter,Venkatesan, Munuswamy,Coey, Michael,Rudolph, Manfred,Vos, Johannes G.,Tacke, Reinhold,Weigand, Wolfgang
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- PROCATALYST COMPOSITION INCLUDING SILYL ESTER INTERNAL DONOR AND METHOD
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The present disclosure provides silyl esters and silyl diol esters suitable as internal electron donors in procatalysts for polymer production. Disclosed are procatalyst compositions formed from a procatalyst precursor and an internal electron donor that is a silyl ester or a silyl diol ester. The procatalyst compositions can be used with a cocatalyst and optionally an external electron donor and/or an activity limiting agent to form a Ziegler-Nana catalyst composition. The present catalyst compositions exhibit high catalyst activity and form olefin-based polymers with broad molecular weight distribution, favorable flexural modulus, and high isotacticity.
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Paragraph 0192; 0193
(2016/11/21)
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- Energetic Sila-Nitrocarbamates: Silicon Analogues of Neo-Pentane Derivatives
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Four silanes based on the neo-pentane skeleton Me4-xSi(CH2R)x containing carbamate groups (x = 1-4, R = OC(O)NH2) have been prepared via the corresponding alcohols Me4-xSi(CH2OH)x, starting from the chlorosilanes Me4-xSiClx. Subsequent nitration leads to the corresponding primary nitrocarbamates (R = OC(O)NHNO2), examined for the purpose as potential energetic materials, including the silicon analogue of pentaerythritol tetranitrocarbamate (sila-PETNC) and a siloxane based nitrocarbamate side-product. All compounds were thoroughly characterized by spectroscopic methods including X-ray diffraction. Thermal stabilities and sensitivities toward impact and friction were examined, as well as detonation values by calculating energies of formation using the EXPLO5 V6.02 software.
- Axthammer, Quirin J.,Klap?tke, Thomas M.,Krumm, Burkhard,Reith, Thomas
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p. 4683 - 4692
(2016/05/24)
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