Synthesis and Reactivity of Copper Complexes Possessing Non-dative Ligands PDF Download
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Languages : en
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Author: Elizabeth D. Blue
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ISBN: 9780549076230
Category :
Languages : en
Pages : 194
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Presented herein are the isolation and characterization of a number of new copper(I) halide complexes and the first two examples of monomeric copper(I) amido complexes, (dtbpe)Cu(NHPh) and (IPr)Cu(NHPh). These Cu(I) anilido complexes have been shown to be more nucleophilic than a related Ru(II) anilido complex in reactivity studies with bromoethane, and reveal increasing nucleophilicity in the order (SIPr)Cu(NHPh) < (IPr)Cu(NHPh) < (IMes)Cu(NHPh) < (dtbpe)Cu(NHPh). (IPr)Cu(NHPh) is thermodynamically favored over (IPr)Cu(Ph)/NH2Ph or [(IPr)Cu(mu-H)]2/NH2Ph, respectively. Computational studies are consistent with the observed reactivity and indicate strong Cu-N bonds with nucleophilic amido nitrogen.
Author: Colleen Munro-Leighton
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Category :
Languages : en
Pages : 252
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Keywords: hydroamination, copper(I), platinum(IV), platinum(II), hydroalkoxylation, hydrothiolation, C-H activation.
Author: Aalo Kumar Gupta
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Languages : en
Pages : 244
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Languages : en
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Examples of late transition metal complexes with amido, alkoxo and sulfido ligands are relatively rare in part due to enhanced reactivity based on nucleophilicity and basicity of the heteroatomic ligand (X). The highly nucleophilic and basic character of formally anionic X ligands coordinated to metal centers with low oxidation states is attributable to the disruption of ligand-to-metal pi-bonding. Examples of common reactivity for these systems include nucleophilic addition reactions, insertions of unsaturated substrates, acid/base chemistry with acidic C-H bonds and C-H activation reactions with aromatic substrates. In addition to fundamental reactivity studies, these complexes also offer opportunities for incorporation into catalytic processes. Late transition metal complexes with non-dative X ligands have been implicated in several C-X bond forming reactions and have been demonstrated to activate non-polar substrates. Thus, in order to advance the understanding of these reactive systems and to exploit the prospects for synthetic applications toward small molecule transformations, further study is warranted. Presented herein is the study of (IPr)Cu(NR2), (IPr)Cu(OR) and (IPr)Cu(SR) {IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene} complexes in the catalytic hydroamination of electron-deficient olefins toward regioselective formation of C-N, C-O and C-S bonds. The substrate scope encompasses alkyl and aryl amines, including primary and secondary variants, as well as alcohols and thiols. Olefins with cyano, acyl, and ester functionalities and vinylarenes are reactive. In a demonstration of potential application, the hydroamination of p-nitrostyrene with N-methylbenzylamine by (IPr)Cu(NHPh) provides a straight-forward single-step route to an anti-arrhythmic agent. Mechanistic studies are consistent with a reaction pathway that involves intermolecular nucleophilic addition of the Cu-amido to free olefin. In an effort to obtain more active catalyst systems that.
Author: Maximilian Joost
Publisher: Springer
ISBN: 3319186906
Category : Science
Languages : en
Pages : 244
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This thesis addresses the coordination chemistry and reactivity of copper and gold complexes with a focus on the elucidation of (i) the metal-mediated activation of σ-bonds and (ii) the migratory insertion reaction. Both processes are of considerable importance in organometallic chemistry, but remain elusive for Cu and Au complexes. In this work, the author contributes significant advances: The first σ-SiH complexes of copper are experimentally and computationally characterized, yielding valuable insights into σ-bond activation processes for copper. Evidence for a highly unusual migratory syn insertion of unsaturated organic molecules into the gold-silicon bond of silylgold (I) complexes is provided and the corresponding mechanism identified. The intermolecular oxidative addition of σ-SiSi, σ-CC and σ-CX (X=halogen) bonds with molecular gold (I) complexes is studied in detail, effectively demonstrating that this reaction, usually considered to be impossible for gold, is actually highly favored, provided an adequate ligand is employed. The use of small-bite angle bis (phosphine) gold (I) complexes allows for the first time the oxidative addition of σ-CC and σ-CX bonds for gold (I). These results shed light on an unexpected reactivity pattern of gold complexes and may point the way to 2-electron redox transformations mediated by this metal, opening up new perspectives in gold catalysis.
Author: Samuel A. Delp
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ISBN:
Category :
Languages : en
Pages : 185
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Author: Andrew C. Lane
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ISBN:
Category :
Languages : en
Pages : 87
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Group 11 transition metals are used daily throughout our bodies and as additives in many common products. One biological function of copper, a group 11 metal, is its use in the Cu A site of cytochrome c oxidase, an enzyme found in the last step of cellular respiration. To model this active site, three formamidinate ligands have been examined: 2,6-dimethylphenyl, 2,6- diisopropylphenyl, and 2,4,6-trimethylphenyl. The synthesis and structural characterization of these dinuclear Cu(I) complexes is described as well as their redox chemistry with I 2 to afford complexes of mixed-valence which is the normal resting state of the Cu A site. Using EPR spectroscopy and DFT calculations on the iodine oxidized products, different electronic structures base d on the formamidinate was found. Additionally, insertion of CS 2 into the copper-nitrogen bonds of the copper(I) formamidinate complexes produces tetra- and hexanuclear clusters based on the steric properties of the ligand
Author: Xuliang Dai
Publisher:
ISBN:
Category : Catalysts
Languages : en
Pages : 512
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Author: Maximilian Joost
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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The present work is a study concerning the coordination chemistry and reactivity of copper and gold complexes. Of particular interest was the elucidation of (i) the metal-mediated activation of s-bonds and (ii) the migratory insertion reaction. Both processes are of considerable importance in organometallic chemistry, but elusive for copper and gold. The first part of this manuscript is dedicated to the study of the coordination of s-SiH bonds to copper. By means of a chelate assistance approach, we synthesized copper complexes employing diphosphino-hydrosilane ligands (R2P(o-C6H4))2Si(R')H. This study allowed for the identification of a weak ?2-SiH coordination to copper that has been evidenced by experimental (NMR, IR, XRD) and computational (geometry optimization, NBO analysis) means. The s-SiH coordination is essentially dominated by donation of electron density from the hydrosilane moiety to copper, without significant backdonation. In the second part, we investigated the reactivity of silylgold(I) complexes towards unsaturated organic molecules. We showed that these complexes react with alkynes and allenes to yield (Beta-silyl)vinylgold complexes via migratory syn insertion into the gold-silicon bond. A mechanistic proposal consisting of a 2-step coordination insertion process was established for this transformation by means of a kinetic and computational study. In the third part, the intermolecular oxidative addition of s-SiSi, s-CC and s-CX (X=halogen) bonds with molecular gold(I) complexes was studied in detail. We showed that this reaction, usually considered to be impossible for gold, is actually highly favored, provided an adequate ligand is employed. Disilanes add to cationic monophosphine gold(I) complexes. However, the corresponding bis(silyl)gold(III) products are highly unstable. The use of bis(phosphine) gold(I) complexes, featuring a bidentate ligand with a small bite-angle, allowed for the first time for the oxidative addition of s-CC and s-CX bonds at gold(I) and proved key for the stabilization of the corresponding gold(III) products that were characterized by spectroscopic and structural means. These results shed light on an unexpected reactivity pattern of gold complexes and may be an entry point to 2-electron redox transformations mediated by this metal, opening up new perspectives in gold catalysis.
