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161.
Formation of High‐Valent Iron–Oxo Species in Superoxide Reductase: Characterization by Resonance Raman Spectroscopy 下载免费PDF全文
Dr. Florence Bonnot Dr. Emilie Tremey Dr. David von Stetten Dr. Stéphanie Rat Dr. Simon Duval Dr. Philippe Carpentier Dr. Martin Clemancey Dr. Alain Desbois Dr. Vincent Nivière 《Angewandte Chemie (International ed. in English)》2014,53(23):5926-5930
Superoxide reductase (SOR), a non‐heme mononuclear iron protein that is involved in superoxide detoxification in microorganisms, can be used as an unprecedented model to study the mechanisms of O2 activation and of the formation of high‐valent iron–oxo species in metalloenzymes. By using resonance Raman spectroscopy, it was shown that the mutation of two residues in the second coordination sphere of the SOR iron active site, K48 and I118, led to the formation of a high‐valent iron–oxo species when the mutant proteins were reacted with H2O2. These data demonstrate that these residues in the second coordination sphere tightly control the evolution and the cleavage of the O? O bond of the ferric iron hydroperoxide intermediate that is formed in the SOR active site. 相似文献
162.
Highly Fluorinated Tris(indazolyl)borate Silylamido Complexes of the Heavier Alkaline Earth Metals: Synthesis,Characterization, and Efficient Catalytic Intramolecular Hydroamination 下载免费PDF全文
Nuria Romero Sorin‐Claudiu Roşca Dr. Yann Sarazin Prof. Jean‐François Carpentier Dr. Laure Vendier Sonia Mallet‐Ladeira Dr. Chiara Dinoi Prof. Michel Etienne 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(10):4115-4125
Heteroleptic silylamido complexes of the heavier alkaline earth elements calcium and strontium containing the highly fluorinated 3‐phenyl hydrotris(indazolyl)borate {F12‐Tp4Bo, 3Ph}? ligand have been synthesized by using salt metathesis reactions. The homoleptic precursors [Ae{N(SiMe3)2}2] (Ae=Ca, Sr) were treated with [Tl(F12‐Tp4Bo, 3Ph)] in pentane to form the corresponding heteroleptic complexes [(F12‐Tp4Bo, 3Ph)Ae{N(SiMe3)2}] (Ae=Ca ( 1 ); Sr ( 3 )). Compounds 1 and 3 are inert towards intermolecular redistribution. The molecular structures of 1 and 3 have been determined by using X‐ray diffraction. Compound 3 exhibits a Sr ??? MeSi agostic distortion. The synthesis of the homoleptic THF‐free compound [Ca{N(SiMe2H)2}2] ( 4 ) by transamination reaction between [Ca{N(SiMe3)2}2] and HN(SiMe2H)2 is also reported. This precursor constitutes a convenient starting material for the subsequent preparation of the THF‐free complex [(F12‐Tp4Bo, 3Ph)Ca{N(SiMe2H)2}] ( 5 ). Compound 5 is stabilized in the solid state by a Ca???β‐Si?H agostic interaction. Complexes 1 and 3 have been used as precatalysts for the intramolecular hydroamination of 2,2‐dimethylpent‐4‐en‐1‐amine. Compound 1 is highly active, converting completely 200 equivalents of aminoalkene in 16 min with 0.50 mol % catalyst loading at 25 °C. 相似文献
163.
Tomislav Suhina Bart Weber Dr. Chantal E. Carpentier Dr. Kinga Lorincz Prof. Dr. Peter Schall Prof. Dr. Daniel Bonn Prof. Dr. Albert M. Brouwer 《Angewandte Chemie (International ed. in English)》2015,54(12):3688-3691
The area of contact between two objects was detected by using the strong enhancement of the fluorescence of rigidochromic probe molecules attached to one of the surfaces. Confinement of the molecules suppresses nonradiative decay and turns on the fluorescence. The approach is demonstrated by imaging of the contact area of a plastic sphere in contact with a flat glass surface. Our results agree excellently with the prediction of Hertz’s classical theory based on elastic deformation. 相似文献
164.
Heterobi‐ and ‐trimetallic Ion Pairs of Zirconocene‐Based Isoselective Olefin Polymerization Catalysts with AlMe3 下载免费PDF全文
Dr. Gabriel Theurkauff Dr. Arnaud Bondon Dr. Vincent Dorcet Prof. Dr. Jean‐François Carpentier Dr. Evgueni Kirillov 《Angewandte Chemie (International ed. in English)》2015,54(21):6343-6346
The reactivity towards AlMe3 of discrete cationic ansa‐zirconocenes 2 a,b that are ubiquitously used in isoselective propylene polymerization and based on [{Ph(H)C(3,6‐tBu2‐Flu)(3‐tBu‐5‐Et‐Cp)}ZrMe2)] {Cp‐Flu} and rac‐[{Me2Si‐(2‐Me‐4‐Ph‐Ind)2}ZrMe2] {SBI} was scrutinized. The first example of a structurally characterized Group 4 metallocene AlMe3 adduct ( 3 b ) is reported. In the presence of excess AlMe3, the {SBI}‐based AlMe3 adduct 3 b undergoes a slow decomposition via C? H activation in a bridging methyl unit to yield a new species ( 4 b ) with a trimetallic {Zr(μ‐CH2)(μ‐Me)AlMe(μ‐Me)AlMe2} core. EXSY NMR data for the process 2 b ? 3 b → 4 b suggest very rapid and reversible binding of an additional AlMe3 molecule onto AlMe3 adduct 3 b . The resulting heterotrimetallic species intermediates exchange of methyl groups between different metal centers and slowly undergoes the C? H activation reaction towards 4 b . 相似文献
165.
Marion Helou Olivier Miserque Jean‐Michel Brusson Jean‐Franois Carpentier Sophie M. Guillaume 《Macromolecular rapid communications》2009,30(24):2128-2135
α,ω‐Dihydroxy‐telechelic poly(trimethylenecarbonate), HO‐PTMC‐OH, is synthesized from the controlled “immortal” ring‐opening polymerization (ROP) of trimethylene carbonate under mild conditions (bulk, 60 °C), using ZnEt2 or, more efficiently, [(BDI)Zn(N(SiMe3)2)] (BDI = CH(CMeNC6H3‐2,6‐iPr2)2) as catalyst precursor, in the presence of a diol HO‐R‐OH (R = (CH2)2 or CH2C6H4CH2; 0.5–10 equiv. vs Zn) acting both as co‐initiator and chain transfer agent. Alternatively, HO‐PTMC‐OH is prepared upon hydrogenolysis of HO‐PTMC‐OCH2Ph, initially prepared from the ROP of TMC using the [(BDI)Zn(N(SiMe3)2)]/PhCH2OH system, under smooth operating conditions using Pd/charcoal. Well‐defined dihydroxy‐functionalized PTMCs of molar mass ranging from = 2 000 to 109 500 g · mol−1 were thus quantitatively obtained and fully characterized by NMR, MALDI‐TOF‐MS and SEC analyses. The versatility of this “immortal” ROP allows the preparation of alike α,ω‐functional polyester such as linear HO‐poly(lactide)‐OH, as well as star polymers such as the glycerol‐based PTM‐OH3.