Development of Nickel(II) Complexes of Oxime Containing Ligands for the Activation of Dioxygen PDF Download
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Author: Michael Joseph Goldcamp
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Languages : en
Pages :
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Ligands containing two oxime donor groups with a variable third group in a tripodal amine motif have been designed and synthesized. Their Ni(II) complexes, and some Zn(II), Cu(II), and Fe(III) complexes, have been structurally and spectroscopically characterized. Deprotonation of the oxime groups gives Ni(II)--Polyoximate complexes that form bis(N-O) oximate bridged dimers with significantly low oxidation potentials for Ni(II). These Ni(II)-polyoximate complexes react with dioxygen, consuming multiple equivalents. This is unusual chemistry for Ni(II), especially in the absence of ligand oxidation. The Ni(II) / O 2 reaction system promotes oxidation of triphenyl phosphine, with oxygen atom transfer, benzyl alcohol, and 3,5-di-tert-butylcatechol. Reaction of the Ni(II)-polyoximate complexes with o-quinones causes the formation of high-valent nickel complexes of the reduced dioxolenes, semiquinones and catecholates.
Author: Michael Joseph Goldcamp
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Category :
Languages : en
Pages :
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Book Description
Ligands containing two oxime donor groups with a variable third group in a tripodal amine motif have been designed and synthesized. Their Ni(II) complexes, and some Zn(II), Cu(II), and Fe(III) complexes, have been structurally and spectroscopically characterized. Deprotonation of the oxime groups gives Ni(II)--Polyoximate complexes that form bis(N-O) oximate bridged dimers with significantly low oxidation potentials for Ni(II). These Ni(II)-polyoximate complexes react with dioxygen, consuming multiple equivalents. This is unusual chemistry for Ni(II), especially in the absence of ligand oxidation. The Ni(II) / O 2 reaction system promotes oxidation of triphenyl phosphine, with oxygen atom transfer, benzyl alcohol, and 3,5-di-tert-butylcatechol. Reaction of the Ni(II)-polyoximate complexes with o-quinones causes the formation of high-valent nickel complexes of the reduced dioxolenes, semiquinones and catecholates.
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Category :
Languages : en
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Ni(II) complexes containing amidates and thiolates have been shown to react with O2 via irreversible ligand oxidation. We have constructed a series of Ni(II) complexes based on a tripodal amine bis(oxime) ligand framework. These complexes display oxygen reactivity upon deprotonation of the oximes without requiring irreversible ligand oxidation. This project investigated the reaction involving one of the complexes in the library, [Ni(TRISOXH3)(NO3)(H2O)](NO3)สบ (H2O), where TRISOXH3 = (tris(1-propan-2-onyl oxime)amine). It was discovered that the reaction of this complex with molecular oxygen is contingent upon the presence of a source of hydrogen atoms. This two-hydrogen atom donor acts as a substrate. Several primary alcohols, including the relatively inert methanol, and amines were catalytically oxidized by this reaction. Spectroscopic analysis using a variety of techniques has demonstrated that reversible oxidation occurs on the oximate nitrogen to form an iminoxyl radical. Many of the other complexes in the series were also investigated to examine their electronic structure, their electrochemical properties, and their ability to oxidize methanol.
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Category : Dissertation abstracts
Languages : en
Pages : 776
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Author: Elizabeth Ann Deters
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Category :
Languages : en
Pages : 120
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A series of mononuclear poly(oxime) amine nickel(II) complexes has been shown to catalyze the oxidation of various substances. To further this work, a series of novel dinucleating ploy(oxime) amine ligands and their nickel complexes were synthesized. During this synthesis, a novel anion dependence on the nuclearity of the complex was discovered and investigated for two of the ligands. All of the dinuclear complexes were shown to catalyze the oxidation of various substances, including methanol, benzyl alcohol, and benzylamine. In addition to the oxygen reactivity, zinc complexes of the poly(oxime) amine ligands were shown to have hydrolysis reactivity. These complexes successfully catalyzed the hydrolysis of p-nitrophenyl acetate. Some preliminary kinetic data for the reaction was also obtained.
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Category : Dissertations, Academic
Languages : en
Pages : 854
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Author: Antonio David Manuel
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Category : Ligands
Languages : en
Pages : 111
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The half-life of the reaction was not affected by deuterium labeling of the acetimino methyl groups but was affected by different substituents in the 4-position of the phenyl groups of the ligand. The reactions caused intraligand C-C bond cleavage with formation of a new C=O double bond, resulting in the complexes [Ni{6-(ArN=CMe)C5H3N-2-C(O)NAr}Cl] (where Ar = 4-X-2,6-iPr2C6H2 and X = H, Cl, or Br) and [Ni{6-(ArN=CCD3)C5H3N-2-C(O)NAr}Cl](where Ar = 2,6-iPr2C6H3). The structures of the complexes [Ni{6-(ArN=CR)C5H3N-2-C(O)NAr}Cl] (where Ar = 2,6-iPr2C6H3 and R = CH3 or CD3) were determined by X-ray crystallography. For all four complexes, the carboxamidato group was identified by a strong band in the infrared spectra assignable to the CO stretching vibration. Furthermore, the new carboxamidato ligands were removed from the metal center and isolated in their neutral form as 6-(ArN=CMe)C5H3N-2-C(O)NHAr (where Ar = 4-X-2,6-iPr2C6H2 and X = H, Cl, or Br) and 6-(ArN=CCD3)C5H3N-2-C(O)NHAr(where Ar = 2,6-iPr2C6H3). Taken together, these results indicate that the activation of dioxygen occurs at the ligand and without an overall oxidation state change at the Ni center. The observed ligand-centered oxygenation in these reactions contrasts with the prevailing metal-centered chemistry of redox-active bis(arylimino)pyridine complexes and demonstrates that they can be directly involved in the activation and conversion of a small molecule.
Author: Chaau Yan Poon
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ISBN:
Category :
Languages : en
Pages : 227
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Dioxygen reduction and water oxidation are critical processes for aerobic life. Developing a better understanding of O-O bond activation and formation mechanisms mediated by metalloenzymes involving first-row transition metals such as Fe and Mn, would provide valuable insights for catalyst and drug development. While synthetic iron and copper oxo species generated from O2 have been extensively studied, the process of manganese dioxygen activation and its intermediates is comparatively unexplored. This dissertation focuses on the synthesis, characterization, and dioxygen reactivity of structurally analogous Mn- and Fe-thiolate complexes with tunable N-heterocyclic amine ligands. Chapter one provides an introduction to oxygen-evolving and oxygen-dependent metalloenzymes containing Mn and Fe metallocofactors. Chapter two highlights how metal ion Lewis acidity and steric properties influence the kinetics and thermodynamics of O2 activation by a series of structurally analogous Mn-thiolate complexes. A total of four high-valent Mn-oxo intermediates were observed along the O2 activation pathway, including MnIIIMnIV(m-oxo)(m-OH) intermediates. Chapter three covers the hydrogen atom transfer activity by the MnIIIMnIV(mu-oxo)(mu-OH) intermediate characterized in chapter two. Chapter four focuses on the synthesis, characterization, and preliminary O2 reactivity of Fe-thiolate complexes that possess a tunable N-heterocyclic amine, wherein a less Lewis acidic FeII species within the structurally analogous series led to the observation of a new O2 activation intermediate. Chapter five discusses the comparison between the structures and reactivities of alkoxide- and thiolate-ligated Mn alkylperoxo species with otherwise identical ligand frameworks, which demonstrates key insight into how the primary coordination sphere of active sites could alter their reactivity.
Author: Frederick W. Nieske
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Category : Complex compounds
Languages : en
Pages : 110
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Author: Joliene Renee Trujillo
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Category : Ligands
Languages : en
Pages :
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The utility of small molecules lies in the ability to alter the structure of the molecule and examine the spectroscopic characteristics as well as the reactivity of the complex. Small molecules are often used to probe mechanistic questions on much more complicated systems, such as enzymes. In 1996 a new form of superoxide dismutase was discovered which had nickel in the active site of the enzyme. This discovery sparked renewed interest in nickel-oxygen chemistry. Small molecules were used to probe different nickel-oxygen structure types and their spectroscopic characteristics, though complete understanding of the implications when altering the small molecules has yet to develop. This thesis addresses macrocycle ligand modifications, the varying ways of synthesizing nickel-oxygen complexes, and the reactivity of the nickel-oxygen adducts with exogenous substrates. The work presented herein, describes the synthesis and characterization of [Ni(tmcyclen)(CO)](OTf). Subsequent oxygen activation by [Ni(tmcyclen)(CO)](OTf) lead to the formation of "side-on" nickel(III) peroxo complex as determined by electronic absorption spectroscopy, electron paramagnetic resonance spectroscopy, and mass spectroscopy. Alternatively, the complex can be synthesized from nickel(II) and reduced oxygen reagents, H2O2 or KO2. Reactivity studies of the [Ni(tmcyclen)(O2)](OTf) with phosphines, sulfides, olefins, activated CH bonds, and substituted phenols were investigated. The reactivity studies completed on the "side-on" nickel(III)-peroxo complex shed light on the electronic characteristics of the complex. This thesis represents the first time a "side-on" nickel(III)-peroxo complex is synthesized from monovalent nickel and dioxygen.
Author:
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Category : Medicine
Languages : en
Pages : 2102
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Book Description
Vols. for 1963- include as pt. 2 of the Jan. issue: Medical subject headings.
