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Activation Of Small Molecules At Iron Complexes In Varying Trigonal Ligand Environments
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Book Synopsis Activation of Small Molecules at Iron Complexes in Varying Trigonal Ligand Environments by : Johannes Hohenberger
Download or read book Activation of Small Molecules at Iron Complexes in Varying Trigonal Ligand Environments written by Johannes Hohenberger and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Ligand Design Considerations for the Activation of Small Molecules by : Sonja Marie Peterson
Download or read book Ligand Design Considerations for the Activation of Small Molecules written by Sonja Marie Peterson and published by . This book was released on 2012 with total page 147 pages. Available in PDF, EPUB and Kindle. Book excerpt: In Nature, the effective control of both the primary and secondary coordination spheres by metal-containing proteins has led to highly efficient and selective catalysts. Much effort has been put forth by the synthetic chemistry community to design complexes that explore the effects of modifying the primary coordination sphere. However, understanding the implications of both coordination spheres together is necessary to ultimately lead to the development of effective synthetic complexes for small molecule activation. For the research described herein, inspiration from biology has led to the design and preparation of ligands, paying special attention to both environments to meet the specific requirements of the small molecules targeted. Chapter 2 discusses the design and synthesis efforts of two new tripodal and tridentate ligands and complexes that feature both a redox-active primary coordination sphere and contain intramolecular H-bond donors in the secondary coordination sphere. This project was in collaboration with the laboratory of Alan Heyduk. Chapter 3 describes the synthesis and characterization of [Co II[superscript] H2bupa]− and [Ni II[superscript] H2bupa]− complexes. The reactivity of both of these complexes with dioxygen was explored in order to detect intermediates during activation yielding proposed Co III[superscript] -superoxo and Ni III[superscript] -hydroxo species. [Co II[superscript] H2bupa]− was also found to reduce dioxygen to water. Water measurements were carried out for [Co II[superscript] H2bupa]− and [Mn II[superscript] H2bupa]− in the presence of an internal standard. The turnover number for these complexes was determined and will also be discussed. Chapter 4 features the synthesis of a new tripodal ligand, H3btspa. It contains the carboxyamidopyridine group reminiscent of H5bupa, but contains two sufonamido groups capable of acting as H-bond acceptors. Upon deprotonation it ready forms complexes with Mn II[superscript], Fe II[superscript], Co II[superscript], and Zn II[superscript] salts. The stability of these complexes will also be described. Chapter 5 discusses nitrogen-containing complexes made from [Fe II[superscript] MST]-. Both the Fe II[superscript] and Fe III[superscript]-ammine complexes were synthesized along with the Fe II[superscript] -hydrazine complex. Attempts to deprotonate the Fe III[superscript]-ammine complex resulted in the reformation of the Fe II[superscript] ammine complex, leading to the proposal of a transient Fe III[superscript]-amido intermediate. Attempts to perform amination chemistry from the Fe II[superscript] and Fe III[superscript]-ammine complexes will also be highlighted.
Book Synopsis Activation of Small Molecules with Iron(II)- and Copper(I)-complexes by : Pascal Specht
Download or read book Activation of Small Molecules with Iron(II)- and Copper(I)-complexes written by Pascal Specht and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Metal-ligand Cooperativity in Low-valent Iron Complexes for Small Molecule Activation by : Nicolas I. Regenauer
Download or read book Metal-ligand Cooperativity in Low-valent Iron Complexes for Small Molecule Activation written by Nicolas I. Regenauer and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Activation of Small Molecules by Some Transition Metal Complexes by : Philip Vasil Yaneff
Download or read book The Activation of Small Molecules by Some Transition Metal Complexes written by Philip Vasil Yaneff and published by . This book was released on 1976 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Catalytic Activation of Small Molecules by Transition Metal Complexes by : Edward Mason Gordon
Download or read book The Catalytic Activation of Small Molecules by Transition Metal Complexes written by Edward Mason Gordon and published by . This book was released on 1987 with total page 456 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Activation of Small Molecules by Transition Metal Complexes Via Computational Methods by : Ahmad Najafian
Download or read book Activation of Small Molecules by Transition Metal Complexes Via Computational Methods written by Ahmad Najafian and published by . This book was released on 2020 with total page 113 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Small Molecule Activation Mediated by Metal-ligand Cooperation Via a Dearomatization/rearomatization Reaction Sequence Using Redox Active Pyridine Based Ligand-systems in Transition Metal Complexes by : Rasmus Stichauer
Download or read book Small Molecule Activation Mediated by Metal-ligand Cooperation Via a Dearomatization/rearomatization Reaction Sequence Using Redox Active Pyridine Based Ligand-systems in Transition Metal Complexes written by Rasmus Stichauer and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Synthesis and Characterization of Transition Metal Complexes with Bulky Tin Ligands for Application in Small Molecule Activation by : Veeranna Yempally
Download or read book Synthesis and Characterization of Transition Metal Complexes with Bulky Tin Ligands for Application in Small Molecule Activation written by Veeranna Yempally and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The role of bulky tin ligands in the stabilization of transition metal complexes with electronic unsaturation has been studied to understand the mode of binding of small molecules at an unsaturated metal center. We were able to isolate electronically unsaturated Pt-Sn bimetallic complexes effective in the reversible activation of small molecules including CO, H2, C2H4, and NH3 at room temperature. We have examined the effect of the modification of ligands in Pt-Sn bimetallic complexes for the activation of small molecules and have observed that the Pt(SnBut3)2(CNBut)2 bimetallic complex reversibly activates hydrogen at room temperature both in the solid state and in solution. Similarly, we have also prepared bimetallic Pt-Sn complexes with an NHC carbine ligand which were also shown to activate hydrogen and alkenes reversibly. A bimetallic Fe-Sn cluster complex, Fe2 ([mu]-SnBut2)2(CO)8, was synthesized from the reaction of But3SnH with the Fe2(CO)9 and shown to be selective at activating the benzylic C-H bond of alkylaromatic solvent molecules. The new complexes containing tin have been characterized spectroscopically to gain an insight into the reaction mechanism involved in small molecule activation.
Book Synopsis Small Molecule Activation of Copper and Iron Complexes with Bis(oxazoline) Ligands by : Vandana Esther Goswami
Download or read book Small Molecule Activation of Copper and Iron Complexes with Bis(oxazoline) Ligands written by Vandana Esther Goswami and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This work describes small molecule activation by copper and iron complexes with structurally and electronically modified bis(oxazoline) (BOX) ligand systems, focusing on dioxygen and nitric oxide as substrates. Dioxygen activation at low temperatures by copper(I) complexes with neutral BOX scaffolds generated the side on peroxo dicopper(II) systems that resemble the intermediates found in type III copper proteins, whereas those complexes with an anionic BOX-derived scaffold generated the bis(μ-oxido) dicopper(III) species. The bis(μ-oxido) system has recently been proposed as an active inte...
Book Synopsis Iron Chemistry of Hemilabile SNS Ligands by : Uttam Das
Download or read book Iron Chemistry of Hemilabile SNS Ligands written by Uttam Das and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The development of abundant and economical first-row transition metal-based catalysts is an appealing area of research for efficient and selective chemical transformations. In this context, iron complexes are highly desirable as they feature a range of accessible oxidation states allowing for transfer of one or two electrons to or from a substrate. Therefore, over the past two decades, many iron-based catalysts have been developed, extensively studied, and exploited for catalysis ranging from oxidation and reduction to C-C bond forming reactions. In homogeneous transition metal catalysis, the ligand plays a vital role in determining activity and selectivity of the above stated catalytic reactions. Some key features of ligands that support both stoichiometric and catalytic reactions of metal complexes include: 1) strong chelation ability to metals, 2) tunability of donor atoms, 3) strong field ligands such as phosphine, phosphite, CO, and hydride favoring low-spin complexes, 4) hemilability allowing substrate activation via reversible dissociation of one donor atom, and 5) redox-activity enabling donation or accepting of electrons, thus avoiding a change of metal oxidation state. To this end, bifunctional ligands containing the above described properties have emerged as important elements in chemical synthesis and in catalysis. Iron and other transition metal complexes containing multidentate bifunctional ligands have recently been shown to activate small molecules and catalyze a number of chemical transformations with activity and selectivity typical of more well-studied precious metals. The objective of this thesis is to further advance the field of bifunctional ligands by preparing new sterically svelte tridentate ligands with a mixture of hard nitrogen and soft sulfur donors and to investigate their iron chemistry. The overall goal is to then explore the utility of these iron complexes as potential bifunctional catalysts. Chapter 2 describes a one-step synthesis of a new SMeNHS ligand in excellent yield that undergoes ring-opening on treatment with Fe(OTf)2 affording a thiolate-bridged, trinuclear iron complex, [Fe3(μ2-SMeNS−)4](OTf)2. The structure, spectroscopic, magnetic, and computational studies of this iron complex are provided along with its solvent-dependent reactivity towards monodentate donor ligands that yields both dinuclear and mononuclear derivatives. Chapter 3 describes the formation of an electron-rich Fe(II) thiolate complex, [Fe(SMeNS)(PMe3)3](OTf) and its substitution reactivity with both mono- and bidentate donor ligands. On heating this complex, an oxidative thioether Caryl-S bond cleavage is observed, leading to a cationic Fe(III)-CNS thiolate analog. Reduction of this Fe(III) species with cobaltocene yielded a neutral Fe(II)-CNS thiolate complex. To investigate the bifunctional activity of these Fe(II) complexes, both Fe(II)-SNS and -CNS species were assessed as precatalysts for amine-borane dehydrogenation. Chapter 4 employs the SMeNHS ligand in formation of a neutral, imine-coupled Fe-N2S2 complex that serves as an efficient and selective aldehyde hydroboration catalyst using pinacolborane. A reaction profile kinetic analysis implicates the hemilability and redox-active properties of this complex. Chapter 5 introduces the new unsymmetrical amine ligand, SMeNHSMe, and details its iron chemistry with formation of a pseudooctahedral Fe(II) bis(amido) complex. The Mössbauer spectra, MCD study, and DFT calculations support formation of a minor five-coordinate isomer in solution due to the hemilability of the six-membered ring thioether group. Reactivity studies of this Fe(II) species with a variety of donor ligands confirmed this lability and protonation at nitrogen yielded a cationic Fe(II) amine-amido complex. Reaction of the latter with the tridentate phosphine, triphos, gave a 16e-, low-spin, square-pyramidal Fe(II) complex that proved to be a robust precatalyst that is more active for dehydrogenation of dimethylamine-borane vs. ammonia-borane. Formation of a monohydride catalyst resting state under these reaction conditions is suggestive of a bifunctional activation pathway. Finally, Chapter 6 concludes the outcomes of the iron chemistry of hemilabile SNS ligands and discusses future directions and opportunities to extend these ligand systems to other transition metals. The knowledge gained by the stoichiometric and catalytic reactivity of iron-SNS complexes presented herein contributes to our understanding of bifunctional catalysis. With the increasing demand for base metal catalysts in chemical industry for efficient and selective synthesis of value-added chemicals, iron SNS complexes could offer economical, active, and selective catalyst precursors.
Book Synopsis Biological Inorganic Chemistry by : Ivano Bertini
Download or read book Biological Inorganic Chemistry written by Ivano Bertini and published by University Science Books. This book was released on 2007 with total page 794 pages. Available in PDF, EPUB and Kindle. Book excerpt: Part A.: Overviews of biological inorganic chemistry : 1. Bioinorganic chemistry and the biogeochemical cycles -- 2. Metal ions and proteins: binding, stability, and folding -- 3. Special cofactors and metal clusters -- 4. Transport and storage of metal ions in biology -- 5. Biominerals and biomineralization -- 6. Metals in medicine. -- Part B.: Metal ion containing biological systems : 1. Metal ion transport and storage -- 2. Hydrolytic chemistry -- 3. Electron transfer, respiration, and photosynthesis -- 4. Oxygen metabolism -- 5. Hydrogen, carbon, and sulfur metabolism -- 6. Metalloenzymes with radical intermediates -- 7. Metal ion receptors and signaling. -- Cell biology, biochemistry, and evolution: Tutorial I. -- Fundamentals of coordination chemistry: Tutorial II.
Book Synopsis Activation of Small Molecules by Multidentate Diphosphino Late Transition Metal Complexes by : Junghee Seo
Download or read book Activation of Small Molecules by Multidentate Diphosphino Late Transition Metal Complexes written by Junghee Seo and published by . This book was released on 2015 with total page 202 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Early-Late Heterobimetallic Complexes Linked by Phosphinoamide Ligands by :
Download or read book Early-Late Heterobimetallic Complexes Linked by Phosphinoamide Ligands written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent attention in the chemical community has been focused on the energy efficient and environmentally benign conversion of abundant small molecules (CO2, H2O, etc.) to useful liquid fuels. This project addresses these goals by examining fundamental aspects of catalyst design to ultimately access small molecule activation processes under mild conditions. Specifically, Thomas and coworkers have targetted heterobimetallic complexes that feature metal centers with vastly different electronic properties, dictated both by their respective positions on the periodic table and their coordination environment. Unlike homobimetallic complexes featuring identical or similar metals, the bonds between metals in early/late heterobimetallics are more polarized, with the more electron-rich late metal center donating electron density to the more electron-deficient early metal center. While metal-metal bonds pose an interesting strategy for storing redox equivalents and stabilizing reactive metal fragments, the polar character of metal-metal bonds in heterobimetallic complexes renders these molecules ideally poised to react with small molecule substrates via cleavage of energy-rich single and double bonds. In addition, metal-metal interactions have been shown to dramatically affect redox potentials and promote multielectron redox activity, suggesting that metal-metal interactions may provide a mechanism to tune redox potentials and access substrate reduction/activation at mild overpotentials. This research project has provided a better fundamental understanding of how interactions between transition metals can be used as a strategy to promote and/or control chemical transformations related to the clean production of fuels. While this project focused on the study of homogeneous systems, it is anticipated that the broad conclusions drawn from these investigations will be applicable to heterogeneous catalysis as well, particularly on heterogeneous processes that occur at interfaces in multicomponent systems.
Book Synopsis Electronic Tunings in Biomimetic Iron Complexes for Small Molecule Activation by : Teera Chantarojsiri
Download or read book Electronic Tunings in Biomimetic Iron Complexes for Small Molecule Activation written by Teera Chantarojsiri and published by . This book was released on 2015 with total page 227 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Activation of Small Molecules by Low Valent Corrole Metal Complexes by : Inna Luobeznov
Download or read book Activation of Small Molecules by Low Valent Corrole Metal Complexes written by Inna Luobeznov and published by . This book was released on 2007 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Small Molecule Binding to Electrophilic Trigonal Pyramidal Platinum, Palladium, and Nickel by : Charlene Tsay
Download or read book Small Molecule Binding to Electrophilic Trigonal Pyramidal Platinum, Palladium, and Nickel written by Charlene Tsay and published by . This book was released on 2013 with total page 266 pages. Available in PDF, EPUB and Kindle. Book excerpt: Chapter 1 A general introduction to the concepts and background of several types of transition metal complexes that motivate and inform the research described herein. These include a-complexes and molecular adducts of dinitrogen, dihydrogen, and carbon dioxide. Chapter 2 Trigonal bipyramidal platinum(II) complexes of the monoanionic, tetradentate, triphosphine [SiPR3 ([SiP3R]- = [(2-R2PC6H4)3Si]-; R = Ph, iPr) ligand are prepared and shown to provide access to cationic species with divergent behavior. The less electron-rich phenyl-substituted ligand renders the platinum center extremely electrophilic, leading to structurally characterized examples of weakly-donating ligands bound in the fifth, apical coordination site. Of particular interest is the structure of the toluene adduct, which suggests a possible interaction between the platinum center and an aryl C-H bond. When the ligand phosphines are instead substituted by the more electron-rich isopropyl groups, the electrophilicity of the cationic platinum is shown to be mitigated, allowing access to a four-coordinate, trigonal pyramidal platinum center. The crystallographically characterized geometry for this divalent platinum is in contrast to the canonical square planar configuration for d8, 16-electron transition metal complexes. The palladium analogue is also synthesized and shown to possess the same coordination. Chapter 3 Cationic nickel complexes of the [SiPR3] ligand are synthesized and, in contrast to their platinum and palladium congeners, facilitate the surprising binding of molecular dinitrogen to electrophilic nickel(II) centers. The extremely high stretching frequencies of these bound N2 moieties attest to their minimal activation, and the stability of these complexes is shown to arise from increased adonation from the N2 to the cationic nickel center, which compensates for the relative lack of it back-bonding that stabilizes N2 adducts in less electrophilic systems. These cationic nickel species are additionally shown to form thermally stable adducts of molecular dihydrogen. The relative binding strengths of N2 and H2 to these nickel centers are explored and shown to be modulated by the ligand phosphine substituents. Furthermore, evidence of linear binding of carbon dioxide is presented, representing an electrophilic approach to carbon dioxide activation that is in contrast to the low-valent, nucleophilic metal paradigm. Chapter 4 The four-coordinate neutral nickel boratrane (TPiPrB = (2-iPr2PC6H4)3B) reported in the literature represents an isostructural counterpart to the cationic {[SiiPr3]Ni}+ species presented in Chapter 3. Though these two compounds are formally separated by two oxidation states of nickel, the Lewis-acidic nature of the Z-type borane ligand in (TP'PrB)Ni renders it valence-isoelectronic with {[SiiPr3]Ni}+. The reactivity toward N2 and H2 of (TPiPr'B)Ni, as well as that of the new compound (TPPhB)Ni, is explored and discussed in context of what is observed for the {[SiPR3]Ni}+ system. The neutral (TPiPr'B)Ni, while presumably a better [pi] back-bonder than cationic {I[SiPip' 3]Ni}T, is demonstrated not to bind N2, though a very weak, fluxional interaction with H2 at low temperature is hypothesized. The more electrophilic (TP PhB)Ni exhibits room temperature interactions with both N2 and H2, though the nature of these interactions has yet to be confirmed. These results thus underline the importance of [sigma]-donation in stabilizing N2 and H2 adducts of poorly 7r back-bonding metal centers. Chapter 5 Cobalt(I) complexes of [SiPR3] provide an additional isostructural, isoelectronic point of comparison to the cationic nickel species presented in Chapter 3. The dinitrogen adducts [SiP'i' 3]Co(N2) and [SiPPh3]Co(N2), previously reported from our laboratory, feature strongly bound N2 ligands that are not labile to vacuum. The corresponding dihydrogen adducts are generated slowly under an H2 atmosphere. The intact nature of both dihydrogen ligands, which also are not labile to vacuum, is reflected in their NMR spectroscopic parameters. The thermal stability of these compounds enabled crystallization of [SiPi'' 3]Co(H2) which, along with the related (TP'i'B)Co(H2) complex also developed in our laboratory, represent the first structurally characterized dihydrogen adducts of cobalt. Additional comparisons are made between the relative N2 and H2 binding strengths of this system and those of the structurally and electronically related family of [SiPR3] and (TpRB) metal complexes. Appendix A The asymmetric dinucleating ligand [NOPPh], designed to contain both a hard, N-donor binding site and a soft-P-donor binding site, is synthesized and shown to form a diiron complex that features asymmetric bonding to the bridging acetates. The corresponding symmetric, allphosphine dinucleating ligand [POPPh], proves to be more conducive to further study, and provides access to the symmetric diiron, di-([mu]-bromide) starting material {[POPPh ]Fe 2Br2} {BArF4 }. Addition of hydrazine generates the asymmetric, unbridged N2H4 adduct, which features localized diamagnetic and paramagnetic iron centers. The conformation of this species additionally demonstrates the flexibility of this ligand framework. Reduction of the diiron(II) starting material in the presence of PMe3 results in formation of a putative asymmetric iron(O)/iron(I) dimetallic complex, in which an N2 molecule is bound to the diamagnetic iron center, while the PMe3 is ligated to the high-spin iron center and rendered NMR silent. The N2 ligand is shown to be reversibly displaced by H2 , suggesting the formation of a dihydrogen adduct, as well as by CO2, which is postulated to bind as a bent, [eta]2(C,O) ligand.
