Download or read book Synthesis Characterization and Reactivity Studies of Iron Complexes Supported by the Redox active ONO Ligand written by Janice Lin Wong and published by . This book was released on 2014 with total page 123 pages. Available in PDF, EPUB and Kindle. Book excerpt: The work reported herein primarily focuses on the development of new platforms for multi-electron reactivity using iron complexes supported by a redox-active pincer-type ligand. This dissertation details the synthesis, characterization, and reactivity of iron complexes coordinated to the redox-active [ONO] ([ONO]H3 = bis(3,5-di-[tert]-butyl-2-phenol)amine) ligand. Chapter 1 provides a general background on ligand-centered and metal-centered redox reactivity. Specifically, the characteristics of redox-active ligands and their ability to promote multi-electron reactivity at redox-inert metal centers is presented. In addition, iron-catalyzed organic transformations in which the metal center undergoes redox changes is also discussed. Finally, ligand-enabled redox reactions mediated by iron complexes containing redox-active ligands is described. Chapter 2 reports on the complexation of bis(3,5-di-[tert]-butyl-2-phenoxy)amine, [ONHO], and the redox-active [ONO] ligands by iron centers to afford a new family of iron complexes. Characterizations of each compound through a battery of analytical techniques reveal the oxidation states of the metal center and ligand. Furthermore, the electronic properties of each complex were investigated in order to evaluate their potential to facilitate multi-electron reactivity. Chapter 3 details the reactivity of the [ONO]Fe platform. Metathesis reactions are conducted with [ONO [superscript q] Fe [superscript III] X2 (X = Cl, N[SiMe3]2 complexes, demonstrating the capability of the fully-oxidized [ONO [superscript q]−1 to act as a two-electron acceptor to generate the fully reduced [ONO [superscript cat]3− that is coordinated to an iron(III) center. Similarly, oxidation of [ONO[superscript cat] Fe [superscript III] (py)3 (py = pyridine) using dihalogens result in two-electron oxidations of the tridentate ligand while the metal oxidation state remains the same. These redox reactions showcase the ability of the [ONO] ligand platform to undergo reversible two-electron oxidation state changes, allowing multi-electron reactivity to occur at the iron center. The synthesis and characterization of two novel bimetallic complexes of the form [ONO]M'[ONO]2 M (M' = Fe, Zn; M = Fe) are presented in Chapter 4. The rich redox profiles of both complexes suggest that they can potentially impart unique cooperative bimetallic reactivity. The synthetic techniques developed to prepare these complexes lay the foundation for a general method to access new bimetallic combinations that could be promising for multi-electron reactivity. Finally, Chapter 5 discusses the synthesis, characterization, and electronic comparisons between two homoleptic tris-iminosemiquinonate chromium(III) compounds. While one is coordinated to three N,N'-bis(3,5-dimethylphenyl)acenapthenediimino-semiquinonate, (dmp-ADI [superscript sq])1−, ligands, the other contains three N,N'-bis(3,5-dimethylphenyl)phenanthrenediimino-semiquinonate, (dmp-PDIsq)1− ligands. The differences in the electronic properties between each complex likely stems from variation in the diimine ligand backbones. However, further investigation is required to completely understand the complicated behaviors of such complexes, both of which apparently exhibit intramolecular anti-ferromagnetic properties.
Download or read book The Synthesis Characterization and Oxidation state Dependent Reactivity of Rh I Complexes Formed from Novel Redox active Ligands written by Caroline Cassano Slone and published by . This book was released on 1997 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Synthesis Structural and Electronic Properties and Reactivity of Group 5 Metal Complexes Incorporating the Redox active ONO Ligand Platform written by Steven Paul Hananouchi and published by . This book was released on 2014 with total page 67 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis describes the synthesis, electronic and structural properties, and reactivity of Group 5 metal complexes incorporating the [ONO] ligand platform. A study of the electronic and structural properties of the Group 5 metal complexes incorporating the [ONO] ligand is performed. Once the electronic properties of the complexes are known, the reactivity of the complexes is compared. Chapter 1 describes a brief history of redox-active ligands. The previously published results of redox-active ligands acting as an electron source are discussed. In Chapter 2, the synthesis and electronic and structural properties of metal dichlorides and trichlorides of Group 5 metal complexes incorporating the [ONO] ligand and comparing the metal-ligand cooperativity are performed. In Chapter 3, the synthesis and reactivity of [ONO]NbMe2 and the reactivity of reduced species of [ONO]V(L)n are discussed.
Download or read book Synthesis Reactivity and Multi electron Redox Behavior of a Bis phenoxy amide Ligand Coordinated to a Tantalum Metal Center written by Ryan A. Zarkesh and published by . This book was released on 2012 with total page 150 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation describes the synthesis and reactivity of tantalum metal complexes containing a tridentate redox-active ligand. Fundamental studies have focused on utilizing the redox-active ligand to store multiple electron equivalents for oxidative addition and reductive elimination reactions. Chapter 1 provides an introduction to the characteristics of redox-active ligands and provides an overview of group transfer reactions involving redox-active ligands. The previous published results of bidentate redox-active ligands coordinated to Group IV d0 metals are discussed in terms of their decomposition side reactions. Chapter 2 describes the coordination of a known tridentate redox-active bis(phenoxy)amide ligand, (ONO), to a d0 tantalum(V) metal center and the examination of the redox properties of the resulting chloro oxidation products by electrochemical and spectroscopic methods. Chapter 3 examines the reactivity of the (ONO)TaR2 complexes in the general context of organometallic chemistry with a focus on protonolysis and reactivity with aryl azides, a known source of nitrene fragments upon oxidation. Chapter 4 examines the reactivity of the (ONO)TaX2 (X = Me, Cl) compounds with bulky diazoalkanes, a known carbene transfer reagent. The (ONO)TaCl2 complex proved to be a competent catalyst to generate cyclopropanes from styrene and the corresponding diazoalkane. Chapter 5 explores the utilization of the (ONO) ligand to store electron equivalents for the catalytic nitrene-nitrene coupling reactions with organoazides to afford organodiazenes. Finally, Chapter 6 addresses the electronic considerations of a related redox-active triamido ligand in an effort to tune the ligand's redox potentials.
Download or read book Synthesis and Characterization of Iron Complexes Supported by Bulky Amide Ligands written by Sheree Lynell Stokes and published by . This book was released on 1998 with total page 378 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Synthesis Characterization and Reactivity of Iron Complexes with N donor Ligands in Relation to Oxygenation of Hydrocarbons written by Remle Çelenligil-Çetin and published by . This book was released on 2004 with total page 766 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Synthesis of Reactive Metal Complexes Supported by 1 1 disubstituted Ferrocene Ligands written by Jonathan Lee Brosmer and published by . This book was released on 2017 with total page 155 pages. Available in PDF, EPUB and Kindle. Book excerpt: Reliable transformation of low-cost rare-earth metal oxides to organometallic rare-earth metal complexes is a prerequisite for the advancement of non-aqueous rare-earth metal chemistry. We have recently developed an in situ method to prepare rare-earth alkyl and halide precursors supported by a diamidoferrocene NNfc, 1,1'-fc(NSiMe2Bu)2, as an ancillary ligand. We extended the scope of this method to other lanthanide ions including those that are redox active, such as cerium, praseodymium, samarium, terbium, thulium, and ytterbium. Specifically, samarium trisbenzyl could be generated in situ and then converted to the corresponding samarium benzyl or iodide complexes in good yield. However, it was found that ytterbium trisbenzyl could not be formed cleanly and the consequent conversion to ytterbium iodide complex was low yielding. By adapting an alternative route, the desired ytterbium chloride precursor could be obtained in good yield and purity. The synthesis and characterization of two yttrium alkyl complexes supported by a bisphosphinimine ferrocene ligand, NPfc (1,1 -di(2,4-di-tert-butyl-6-diphenylphosphiniminophenoxy)ferrocene), were accomplished. Although (NPfc)Y(CH2Ph) and (NPfc)Y(CH2SiMe3) could be structurally characterized, these compounds are thermally sensitive and decompose at ambient temperature within hours. Their characterization was accomplished by NMR spectroscopy, electrochemical measurements, and elemental analysis. Reactivity studies were also carried out; however, the lack of prolonged thermal stability at ambient temperature of these molecules led to decomposition before a clean transformation to reaction products could be observed. The synthesis and characterization of Ln-C4Ph4-K, [(NNTBS)Ln( 2-C4Ph4)][K(THF)x] (Ln = Sc, Y, Lu), rare-earth metal complexes supported by a ferrocene diamide ligand, NNTBS (NNTBS = fc(NSitBuMe2)2, fc = 1,1 -ferrocenediyl), were accomplished. The preparation of the half-sandwich compounds, Ln-naph-K, [(NNTBS)Ln( -C10H8)][K(THF)2] (Ln = Sc, Y, Lu, La), was necessary in order to obtain high yields of rare-earth metallacyclopentadienes. Unlike Y and Lu, La did not show the same reactivity toward PhCCPh. The characterization of the new metal complexes was accomplished by NMR spectroscopy, elemental analysis, and single-crystal X-ray diffraction.
Download or read book Synthesis Reactivity and Computational Studies of Redoxactive Indium Thiolate Complexes written by Padmapriya Srinivasan and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Green Chemistry initiatives have recently been at the forefront of both industrial and academic communities in order to address fundamental scientific challenges of protecting human health and the environment. The Twelve Principles of Green Chemistry, of which catalysis is a primary tenet and the main motivation for this project, has led the path to reduce waste production in the chemical industry. The principle of catalysis states that catalytic reactions necessarily produce less waste than stoichiometric reactions. Traditionally, precious and toxic heavy transition metals such as platinum and palladium have been used as metal centres in catalysts because of their stability, favourable redox properties, and ease of characterization. These concerns prompted this research in finding more environmentally friendly alternatives as metal centres in catalysis, such as main group complexes. Indium is a heavy main group metal that is environmentally benign. It is most stable in the +3 oxidation state and, notably, does not possess other readily accessible oxidation states. To make indium complexes redox-active, so-called "non-innocent" redox-active ligands are being explored. The current work seeks to synthesize a series of redox-active indium catalysts with varied steric bulk about the indium centre and different redox-active ligands. The goals of this study are to first synthesize and structurally characterize organometallic indium compounds with the redox-active ligand 2-amninobenzenethiol, and then test the reactivity of indium complexes with dithiolate ligands using mild oxidizing agents. A third goal is to use DFT methods to rationalize the synthesized complexes in terms of structure, reactivity, bonding motifs, and in interpreting the experimental spectroscopic data.
Download or read book Redox Active Ligands written by Marine Desage-El Murr and published by John Wiley & Sons. This book was released on 2024-01-31 with total page 373 pages. Available in PDF, EPUB and Kindle. Book excerpt: Redox-Active Ligands Authoritative resource showcasing a new family of ligands that can lead to better catalysts and promising applications in organic synthesis Redox-Active Ligands gives a comprehensive overview of the unique features of redox-active ligands, describing their structure and synthesis, the characterization of their coordination complexes, and important applications in homogeneous catalysis. The work reflects the diversity of the subject by including ongoing research spanning coordination chemistry, organometallic chemistry, bioinspired catalysis, proton and electron transfer, and the ability of such ligands to interact with early and late transition metals, lanthanides, and actinides. The book is divided into three parts, devoted to introduction and concepts, applications, and case studies. After the introduction on key concepts related to the field, and the different types of ligands and complexes in which ligand-centered redox activity is commonly observed, mechanistic and computational studies are described. The second part focuses on catalytic applications of redox-active complexes, including examples from radical transformations, coordination chemistry and organic synthesis. Finally, case studies of redox-active guanidine ligands, and of lanthanides and actinides are presented. Other specific sample topics covered include: An overview of the electronic features of redox-active ligands, covering their historical perspective and biological background The versatility and mode of action of redox-active ligands, which sets them apart from more classic and tunable ligands such as phosphines or N-heterocyclic carbenes Preparation and catalytic applications of complexes of stable N-aryl radicals Metal complexes with redox-active ligands in H+/e- transfer transformations By providing up-to-date information on important concepts and applications, Redox-Active Ligands is an essential reading for researchers working in organometallic and coordination chemistry, catalysis, organic synthesis, and (bio)inorganic chemistry, as well as newcomers to the field.
Download or read book Redox Activity of Early Metal Complexes Supported by N N bis arylimino acenaphthylene Ligands written by Kensha Marie Clark and published by . This book was released on 2010 with total page 195 pages. Available in PDF, EPUB and Kindle. Book excerpt: Redox-active ligands have been previously shown to enhance reactivity at metal centers by serving as electron reservoirs. This class of ligand facilitates intramolecular electron transfer, enabling reactivity pathways such as oxidative addition and reductive elimination at d0 metal centers. Towards the goal of coupling ligand promoted reactivity with the known reactivity of low-coordinate Group IV imido complexes, the sterics, electronics, and reactivity of the N, N'-bis(arylimino)acenaphthylene (BIAN) ligand set were explored. Initially, the coordination geometry enforced by three BIAN ligand derivatives, dpp-BIAN, tmp-BIAN, and dmp-BIAN (dpp = 2,6-diisopropylphenyl; tmp = 2,4,6-trimethylphenyl; dmp = 3,5-dimethylphenyl), in titanium imido complexes was evaluated. These three ligands present different steric profiles, with dpp-BIAN providing the most steric bulk, while dmp-BIAN ligand offers the least steric protection. In these studies, it was observed that the bulkier ligands, dpp-BIAN and tmp-BIAN, stabilize coordinatively unsaturated imido complexes, (dpp-BIAN)TiCl2(=NR) and (tmp-BIAN)TiCl2(=NR) (R = tBu or 2,6-dimethylphenyl). The dmp-BIAN ligand exclusively forms the six-coordinate amino-imido complexes, (dmp-BIAN)TiCl2(=NR)(NH2tBu). Neutral tris-semiquinonate complexes, M(dmp-BIAN isq)3, of titanium, vanadium, and chromium were structurally, spectroscopically, and electrochemically characterized. From these data, the ability of the BIAN ligand to facilitate intramolecular charge redistribution in early metals was determined. In these complexes, the ligand not only enables reversible redox processes, but antiferromagnetic exchange coupling is observed between the radical ligands and metal ions. The bulky dpp-BAAN ligand, which is the two electron reduced form of dpp-BIAN, was used to make unprecedented mixed-valence cluster complexes of zirconium and hafnium, [(dpp-BAAN)3M3(u2-Cl)3(u3-Cl)2] (M = Zr or Hf). In these complexes the metal centers act as non-discrete redox sites, and an unpaired electron is considered delocalized over the entire molecule. The synthesis and subsequent isolation of these complexes demonstrates the stability that the electronically flexible BIAN ligand set provides. After considering the ligand sterics and electronics, Group IV synthons (dpp-BAAN)MCl2 and (dpp-BAAN)MR2 (M = Ti or Zr; R = Np, CH2Si(CH3)3, or OtBu) were synthesized and characterized. The reactivity of (dpp-BAAN)TiCl2 towards oxidants was evaluated. It was found that this complex successfully undergoes oxidative chloride addition and nitrene addition. Nitrene addition to the (dpp-BAAN)TiNp2 complex results in the unexpected extrusion of bineopentyl from the metal center to generate a putative imido species. Protonolysis of the same synthon similarly forms a putative imido species. The addition of chloride to this species yields a five-coordinate imido complex, (dpp-BIAN)TiCl2(=NR) (R = p-MeCH6), and establishes the basis for further reactivity studies.
Download or read book Synthesis Characterization and Reactivity Studies of Group 2 3 and 4 Metal Complexes Bearing Chelating Amino Siloxide and Alkoxide Ligands written by Pengcheng Patrick Shao and published by . This book was released on 1997 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Expanding the Chemistry of D0 Transition Metals Through Redox active Ligands written by Nicole Annette Ketterer and published by . This book was released on 2008 with total page 368 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Preparation Characterisation and Reactivity of Low Oxidation State d Block Metal Complexes Stabilised by Extremely Bulky Amide Ligands written by Jamie Hicks and published by Springer. This book was released on 2018-06-29 with total page 196 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis describes the synthesis and characterization of numerous metal-metal bonded complexes that are stabilized by extremely bulky amide ligands. It provides a comprehensive overview of the field, including discussions on groundbreaking complexes and reactions, before presenting in detail, exciting new findings from the PhD studies. The thesis appeals to researchers, professors and chemistry undergraduates with an interest in inorganic and/or organometallic chemistry.
Download or read book Design and Synthesis of a Series of Redox Active Tetrazine and Triazine Based Transition Metal Complexes written by Yixin Zhang and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The use of two different chelating redox active ligands, 2,6-bis(6-methyl-1,2,4,5-3-yl) pyridine (BTZP) and 2,6-bis-(5,6-dialkyl-1,2,4-triazin-3-yl)-pyridine (BTP) in heterometallic first row and second row transition metal chemistry has yielded two new families of redox active metal complexes. These complexes were found to exhibit interesting electrochemical and magnetic properties. In this thesis, Chapter 1 lays the foundation for the research presented within. This section covers the fundamentals of the ligand design, ligand synthesis and related coordination chemistry literature review. Chapters 2 and 3 report the results of the current thesis. In Chapter 2, the synthesis and characterization of a family of discrete molecules and supramolecular arrangements, employing the ligand BTZP, is presented. All of the complexes presented in Chapter 2 are successfully synthesized and characterized with electrochemical and magnetic studies. According to the electrochemical data, it is found that the classic "terpy-like" complexes with [Co(BTZP) 2]2+ formula fosters more stability in the redox process. In Chapter 3, a family of transition metal complexes with [M(BTP) 2]2+ (M=Fe or Co) inorganic cores were obtained through the employment of the ligand BTP with various anions. In addition, dimeric molecules with [CoX4(BTP)2] formula were also obtained by solvothermal synthesis. The complexes were also electrochemically characterized, with all the complexes capable of being reduced, while only [CoII(BTP)2] (ClO4)2 showed reversible redox process. Similar with BTZP, the series of BTP based complexes are also characterized through magnetic measurement. Only cobalt-based BTP complexes are paramagnetic, with [CoII(BTP)2]2+ being spin crossover active when BF4- and ClO4- are present. However, the presence of NCS- and halides lead to either antiferromagnetic interactions and ferromagnetic interactions dominating at different temperature regimes.
Download or read book Terdentate Iron Complexes written by Aaron Maurice Tondreau and published by . This book was released on 2011 with total page 409 pages. Available in PDF, EPUB and Kindle. Book excerpt: A three-electron series of four-coordinate bis(imino)pyridine iron nitrosyl complexes was synthesized. The electronic structure of this series of compounds was determined by the use of X-ray crystallography, Mössbauer, IR, NMR, and EPR spectroscopies, and corroborated by DFT calculations. (iPrPDI)Fe(NO) was determined to be an intermediate-spin ferric complex with a triplet two electron reduced bis(imino)pyridine chelate and a triplet NO-. The overall spin state of (iPrPDI)Fe(NO) is S = 1/2. The oxidation of (iPrPDI)Fe(NO) occurs at the bis(imino)pyridine chelate, and the electronic structure of the iron nucleus remains intermediate-spin ferric. The reduction of (iPrPDI)Fe(NO) also is bis(imino)pyridine chelate centered. This yields a three-electron reduced chelate, leaving the iron intermediate-spin ferric and the nitrosyl as NO-. The reduction and oxidation of compounds was carried out to yield two other three-electron series. The synthesis and characterization of [Li(OEt2)3][(iPrPDI)Fe(CH2CMe3)(N2)], (iPrPDI)Fe(CH2CMe3), and [(iPrPDI)Fe(CH2CMe3)][BPh4] allowed for the determination of the degree of chelate participation over a three-electron series pertinent to olefin polymerization. The redox events were shown to occur at the bis(imino)pyridine chelate, leaving the iron nucleus Fe(II) throughout the series. [Na15-Crown-5][(iPrPDI)Fe(CO)2], (iPrPDI)Fe(CO)2, and [(iPrPDI)Fe(CO)2][BArF24] were also synthesized. Analysis of [(iPrPDI)Fe(CO)2][BArF24] indicates that oxidation of the formally Fe(0) complex (iPrPDI)Fe(CO)2 results in the oxidation of the bis(imino)pyridine chelate to a neutral ligand, giving a formally Fe(I) species. [Na-15Crown-5][(iPrPDI)Fe(CO)2] was not structurally characterized, but EPR spectroscopy indicates that the reduction occurred at the ligand, and the iron is low spin Fe(II). Bis(imino)pyridine iron complexes also were utilized as catalysts for the hydrosilylation of ketones, aldehydes, and olefins. The hydrosilylation of ketones and aldehydes was performed with primary and secondary silanes using bis(imino)pyridine iron dialkyl complexes and pybox iron dialkyls. The hydrosilylation of olefins was performed with tertiary silanes utilizing several reduced bis(imino)pyridine iron complexes. The result was reactivity that proved to be competitive with platinum based catalysis. In several instances iron outperformed platinum in terms of selectivity and fewer side-products.
Download or read book Synthesis and Characterization of Redox noninnocent Pyrazine diimine Iron Complexes and an Inverted Pyridine diimine Ligand written by Jaylan Billups and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cooperativity between the metal center and the ligand has been shown in nature to be an important feature of systems that catalyze two-electron processes that first-row transition metals usually cannot catalyze on their own. In these cases, the ligand acts as a site of reactivity that in many instances can store electrons or react directly with substrates in solution. The design and study of systems where there is synergy between the metal and the ligand have been leveraged to catalyze polymerization and hydrogenation-type reactions as well as the activation of small molecules such as dihydrogen. Specifically, the pyridine(diimine) ligand scaffold has been reported to store up to three electrons on the ligand backbone that can later be used in catalysis. Wanting to expand on this work, we have designed and synthesized a new pincer that has redox-noninnocent properties similar to pyridine(diimine) ligands but incorporates a pyrazine ring instead of a pyridine ring to give rise to new electronic properties. Pyrazine(diimines) also have an uncoordinated 4-position nitrogen that can be further functionalized to fine-tune the electronic properties of the ligand. In Chapter II we will discuss bisligated iron(II) pyrazine(diimine) (PZDI) complexes in three different oxidation states where we used spectroscopic and computational techniques as well as comparison to known pyridine(diimine) iron(II) complexes to support our assignments of ligand-based reduction. Chapter III will focus on monoligated pyrazine(diimine) iron(II) complexes as compared to analogous pyrazine(diimine) systems where the central metal is manganese, cobalt, or nickel, as well as compare our pyrazine(diimine) iron(II) complexes to reported pyridine(diimine) iron(II) analogs. We have also synthesized a new inverted pyridine(diimine) ligand scaffold that has an NCN binding pocket, which will be discussed in Chapter IV. In the design of the inverted pyridine(diimine) ligand we have left in place the 4-position nitrogen from our previously described pyrazine(diimine) ligand, maintaining a Lewis basic site for functionalization. Overall, we hope to describe the results we observed with both monoligated and bisligated iron(II) pyrazine(diimine) complexes as well as discuss our approach to the design of and progress towards a new inverted pyridine(diimine) ligand scaffold.
Download or read book Electronic Activation and Tuning of Redox active Ligand Orbitals written by Benjamin Keith Leipzig and published by . This book was released on 2017 with total page 159 pages. Available in PDF, EPUB and Kindle. Book excerpt:
