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Trinuclear Gold Clusters Supported by Cyclic (alkyl)(amino)carbene Ligands: Mimics for Gold Heterogeneous Catalysts 下载免费PDF全文
Dr. Liqun Jin David S. Weinberger Dr. Mohand Melaimi Dr. Curtis E. Moore Prof. Arnold L. Rheingold Prof. Guy Bertrand 《Angewandte Chemie (International ed. in English)》2014,53(34):9059-9063
The synthesis of air‐ and moisture‐stable trinuclear mixed‐valence gold(I)/gold(0) clusters is described. They promote the catalytic carbonylation of amines under relatively mild conditions. The synthetic route leading to the trinuclear clusters involves a simple ligand exchange from the readily available μ3‐oxo‐[(Ph3PAu)3O]+ complex. This synthetic method paves the way for the preparation of a variety of mixed‐valence gold(I)/gold(0) polynuclear clusters. Moreover, the well‐defined nature of the complexes demonstrates that the catalytic process involves a rare example of a definite change of oxidation state of gold from Au02AuI to AuI3. 相似文献
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A series of new acyclonucleosides analogues 3 has been synthesized very efficiently in three steps starting from beta-amino alcohols 1. The key step of this process is a nucleophilic substitution with various nucleophiles on 2,2'-anhydronucleosides 2. The chemo- and stereoselectivities of this reaction are discussed. AM1 calculations sustained the observed chemoselectivity. 相似文献
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Steffen Styra Dr. Mohand Melaimi Dr. Curtis E. Moore Prof. Arnold. L. Rheingold Timo Augenstein Prof. Dr. Frank Breher Prof. Guy Bertrand 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(23):8441-8446
A stable cyclic (alkyl)(amino)carbene (CAAC) 1 inserts into the para‐CF bond of pentafluoropyridine, and after fluoride abstraction, the iminium‐pyridyl adduct [ 3 ]+ was isolated. A cyclic voltammetry study shows a reversible three‐state redox system involving [ 3 ]+, [ 3 ] ? , and [ 3 ] ? . The CAAC‐pyridyl radical [ 3 ] ? , obtained by reduction of [ 3 ]+ with magnesium, has been spectroscopically and crystallographically characterized. In contrast to the lack of π communication between the CAAC and the pyridine units in cation [ 3 ]+, the unpaired electron of [ 3 ] ? is delocalized over an extended π system involving both heterocycles. 相似文献
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Reaction of dimesityl-1,8-naphthalenediylborate (1) with C6F5HgCl results in the formation of a B/Hg heteronuclear bidentate Lewis acid (2), which complexes fluoride to afford [2-mu2-F]-. Structural and photophysical studies carried out in solution and in the solid state indicate that 2 is a highly selective and sensitive phosphorescent fluoride sensor. The proximity of the two Lewis acidic sites enforced by the 1,8-naphthalenediyl backbone promotes fluoride anion chelation and is, therefore, responsible for the high binding constant. The interplay of conjugative and spin-orbit coupling effects mediated by the boron and mercury atoms, respectively, results in the phosphorescent signaling of fluoride binding. Remarkably, fluoride binding occurs in partially aqueous solutions and results in a drastic change of the phosphorescence observed when the solutions are frozen. 相似文献
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[reaction: see text] To verify if hydrogen-bond donor groups can assist fluoride binding at the boron center of triaryl boranes, o-(dimesitylboryl)trifluoroacetanilide has been synthesized. Reaction of this new borane with [n-Bu(4)N][F] in acetone affords the corresponding fluoroborate complex whose stability constant exceeds that of [Mes(3)BF](-) by at least 2 orders of magnitude. Presumably, the higher fluoride affinity of o-(dimesitylboryl)trifluoroacetanilide results from the cooperativity of the Lewis acidic boron center and the hydrogen-bond donor trifluoroacetamide group. 相似文献
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We prove a rgularity result, in Hölder spaces, for solutions to an elliptic problem with mixed boundary condition, namely Dirichlet on a part of the boundary and Signorini on the remaining part, in a regular or polygonal, domain of IR2 We give the behaviour of the solution near points where the boundary condition tyoe changes. Nous montrons la Régularité jusqu'au bord, dans les espaces de Hölder des solutions d'un problème aux limites de type mêlé avec une condition de Dirichlet sur une partie de la frontière et des conditions de type Signorini sur le complémentaire, et ceci dans un ouvert plan ré gulier ou polygonal. Nous donnons en particulier le comportement de la solution au volisinge d'un point de la frontiére où la condition aux limites change de type. Mots Clés: In´quations variationnells–conditions unilatélrales. Domains polygonaux. Classification AMS 35 (J) 49 (A) 相似文献
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Cover Picture: Controlled Expansion of a Strong‐Field Iron Nitride Cluster: Multi‐Site Ligand Substitution as a Strategy for Activating Interstitial Nitride Nucleophilicity (Angew. Chem. Int. Ed. 40/2018) 下载免费PDF全文
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Dr. Dominik Munz Dr. Jiaxiang Chu Dr. Mohand Melaimi Prof. Dr. Guy Bertrand 《Angewandte Chemie (International ed. in English)》2016,55(41):12886-12890
The synthesis of N‐heterocyclic carbene (NHC)–cyclic (alkyl)(amino) carbene (CAAC) heterodimers is presented. As the free carbenes do not react together in solution, the synthetic approach involves the addition of a free NHC to a cyclic iminium salt, which results in the formation of the protonated heterodimer. Subsequent deprotonation leads to the isolation of the corresponding mixed Wanzlick dimers. One‐ and two‐electron oxidations of these triazaolefins result in the formation of stable cationic radicals and bis(cations), respectively, which have been isolated and fully characterized. Cyclic voltammetry, UV/Vis spectroscopy, spin density, and DFT calculations suggest that these heterodimers feature complementary electronic properties to tetrathiafulvalenes (TTFs). 相似文献
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As part of our ongoing interest in the synthesis and reduction chemistry of organoboron species, we have investigated the synthesis of mixed organoboron/organomercury complexes by reaction of the Li(THF)4 salt of dimesityl‐1, 8‐naphthalenediylborate with 1, 2‐(HgCl)2C6F4 and 1, 3‐(HgCl)2C6F4, respectively. The resulting tetranuclear B2Hg2 complexes ( 2 and 3 , respectively) were characterized by multinuclear NMR spectroscopy and single‐crystal X‐ray analysis. The cyclic voltammogram of complex 2 , which features a B–Hg–Hg‐B core connected by an ortho‐phenylene (Hg–Hg connection) and two peri‐naphthalenediyl linkers (B–Hg connection), shows significant coupling of the two electroactive boryl units, presumably via a direct σ interaction of the vacant p orbitals of the four neighboring Lewis acids. This conclusion is supported by DFT calculations, which show that the LUMO of 2 spans the four Lewis acids, with a major in phase contribution from the boron 2p orbitals and the mercury 6p orbitals. 相似文献