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| Author | : Miles William Burrows |
| Publisher | : |
| Total Pages | : 350 |
| Release | : 2002 |
| Genre | : Ligands |
| ISBN | : |
| Author | : Swiatoslaw Trofimenko |
| Publisher | : World Scientific |
| Total Pages | : 294 |
| Release | : 1999-08-16 |
| Genre | : Science |
| ISBN | : 1783261994 |
This book deals with polypyrazolylborates (scorpionates), a class of ligands known since 1966, but becoming rapidly popular with inorganic, organometallic and coordination chemists since 1986, because of their versatility and user-friendliness. They can be readily modified sterically and electronically through appropriate substitution on the pyrazole ring and on boron, and have led to a number of firsts in coordination chemistry (first stable CuCO complex, first monomeric MgR complex, and many other such firsts). Their denticity can range from two to four, their “Bite” can be adjusted, and additional coordinating sites can be added to the pyrazolyl rings. Over 170 different scorpionate ligands are known today, and some are published for the first time in this book.The author, Swiatoslaw Trofimenko, discovered and developed this ligand system and has written several reviews on the subject. The book is intended as a reference work, placing at the researcher's command practically all of the over 1500 references on the subject up, and into 1999, organized both according to the ligand type and according to the metal or metalloid being coordinated. It acquaints the reader with the special features of this ligand system and permits an assessment of what has been done in a given sub-area, and of which areas remain relatively unexplored. It presents procedures for ligand synthesis, and also covers their use in catalysis and in the modelling of biologically active substances.
| Author | : Maisara Abdul Kadir |
| Publisher | : |
| Total Pages | : 331 |
| Release | : 2012 |
| Genre | : Coordination compounds |
| ISBN | : |
This thesis provides an account of the synthesis and study of fifteen amide-containing polypyridyl ligands, eleven of which are new compounds. These ligands all possess at least one amide moiety, potentially capable of anion binding and one or more pendant pyridyl donor groups as the metal coordinating sites. A further evolution over previously reported compounds is that a majority of the amide compounds incorporate a pre-organised amide component that will constitute the anion binding region. The alkyl and phenyl spacers were utilised to confer flexibility to these compounds and to extend the spacing between the anion binding moiety and the pendant metal complexing groups. The compounds investigated in this work are divided into three categories; (i) unsymmetrical monoamide ligands that possess one amide functional group, one ester protected carboxylate and one external donor pyridyl moiety; (ii) symmetrical flexible amide ligands that possess two or more internal amide groups and two external pyridyl metal coordinating sites, and; (iii) symmetrical amide bridging ligands that incorporate two di-2-pyridylmethylamine chelating motifs. The coordination chemistry and metallo-supramolecular chemistry of these ligands was investigated with a range of late transition metals including cadmium(II), copper(II), cobalt(II), silver(I), zinc(II) and palladium(II). Palladium(II) precursors, with a selection of monodentate or bidentate chelating ancillary blocking ligands, were utilised to form discrete mono- and dinuclear assemblies with a view to investigating anion complexation in solution. Other transition metal precursors were studied with a focus on the synthesis of coordination polymers that display anion coordinating pockets.
| Author | : Robert J. Hill |
| Publisher | : |
| Total Pages | : 508 |
| Release | : 2005 |
| Genre | : Organic compounds |
| ISBN | : |
| Author | : Andrew F. Ducruet |
| Publisher | : |
| Total Pages | : 0 |
| Release | : 1999 |
| Genre | : |
| ISBN | : |
| Author | : Kwanyi Ng |
| Publisher | : |
| Total Pages | : 171 |
| Release | : 2012 |
| Genre | : |
| ISBN | : 9781267247643 |
The first chapter of this dissertation describes the importance of hydrogen bonding (H-bonding) within the secondary coordination sphere of metal complexes. Particular emphasis is given to the correlations between the structures of metalloenzyme actives and their functions. Classical examples of synthetic metal complexes, which are designed to mimic some of the features of metalloenzyme active sites, are also reviewed. The detection of reactive intermediates in the mononuclear systems has inspired the development of the dinucleating ligands, which is the cornerstone of the work described in this dissertation. In Chapter 2, the synthesis of a (carboxyamido)pyridinepyrazolate (H5bppap) dinucleating ligand is described. Bimetallic iron and cobalt complexes of H5bppap ([MII2H2bppap]+) showed structural differences in both their primary and secondary coordination spheres. The [CoII2H2bppap]+ is 5,5-corodinate while [FeII2H2bppap]+ is 5,6-coordinate. The binding of small molecules into the preorganized ligand cavity is verified by the hydration of [FeII2H2bppap]+ and [CoII2H2bppap]+, leading to the formation of complexes [{CoII(OH)}CoIIH3bppap]+ and [{FeII(OH)}FeIIH3bppap]+, in which only one of the metal centers has a terminal hydroxo ligand. Chapter 3 will present the synthesis and characterization of a dimanganese(II) complex, [MnII2H2bppap]+. The coordination chemistry of the dimanganese(II) analog of H5bppap is considerably different from its iron and cobalt counterparts. The insertion of external ligands into [MnII2H2bppap]+ with simultaneous protonation of the ligand backbone led to the isolation of a series of seven-coordinate dinuclear MnII species, [MnII2([mu]61549;-X)H4bppap]2+. Chapter 4 illustrates the design and synthesis of a dinucleating ligand, 3,5-Bis[bis(N-6-neopentylamino-2-pyridylmethyl)aminomethyl]-1H-pyrazole (H5bnppap). The syntheses and characterization of the corresponding dinuclear bis(hydroxo) complexes, [MII2H4bnppap(OH)2]+ are discussed. These complexes feature the rare terminal bis(OH) moiety within one molecular unit with the MII-OH units are positioned in a syn-configuration, placing the hydroxo ligands in close proximity (ca. 3 Å apart), which may be a prerequisite for water oxidation. The second part of the chapter describes the hydrolytic studies utilizing [CoII2H4bnppap(OH)2]+. Both [CoII2H4bnppap(OH)2]+ and [{CoII (OH)}MIIH3bppap]+ are able to hydrolyze carbon dioxide to give carbonate-bridged complexes. However, only [CoII2H4bnppap(OH)2]+ is able to hydrolyze triphenylborane to triphenylborate. These results indicate that control of the number of hydroxide ligands within the bimetallic cavity could be used as a strategy to regulate activity of metal-hydroxo complexes.
| Author | : Christophe Fliedel |
| Publisher | : |
| Total Pages | : |
| Release | : 2010 |
| Genre | : |
| ISBN | : |
The objective of this thesis was the developement of new polyfunctional ligands families to study, in a first time, their coordination chemistry towards metallic centers, and in a second time, in view of the nature of the species formed their physical and/or catalytic properties. The combination of donor sites which seems the most interesting was based on the association of donors known to form strong interactions with the metals envisaged, like phosphines (P- ) or N-heterocyclic carbenes (CNHC- ), with more labile donors, like a thioether function (S- ). This association allows the formation of systems called "hemilabiles", which showed good candidates for homogenous catalytic applications. Ligands of type: diaminophosphine/thioether: P-, P-, S- have been developed. These ligands showed various coordination modes, from which a large variety of organometallic complexes were obtained. The second target ligands were of type: N-heterocyclique carbenes (NHC), bearing a thioether group on one nitrogen atom from the cycle: S, CNHC or on both nitrogen: S, CNHC, S. Their precursors have been prepared in "ecofriend" conditions and allowing a large variability. The ligands offer also various coordination modes illustrated by their silver(I) and palladium(II) complexes. The catalytic potential of these compounds has been evaluated in the Suzuki- Miyaura cross-coupling reaction and revealed a very good activity towards brominated substrates.
| Author | : Sandra Yvette Boer |
| Publisher | : |
| Total Pages | : 163 |
| Release | : 2016 |
| Genre | : |
| ISBN | : |
Catalysts are in dispensable for society as they are applied in the majority of industrial processes. Catalysts can increase the rate at which a reaction proceeds, but can also selectively produce only one product, thereby preventing side reactions and the production of side products or waste, resulting in more efficient, atom-economical and environmentally benign processes. In homogeneous catalysis, the catalyst often consists of a transition metal that is surrounded by ligands. Reactive or proton-responsive ligands may be envisioned to operate in a synergistic way with the metal to facilitate a chemical process. This concept of metal-ligand cooperation (MLC) has gained a lot of interest over the past decade and is currently a rapidly expanding field of homogeneous catalysis. The research described in this thesis is focused on the development of new metal complexes bearing different proton-responsive ligand systems. More specifically, several bidentate and tridentate types of pyridine-based ligands are described, based on phosphinomethylpyridines, pyridones and pyrazoles. They all exhibit a cooperative character in their own specific way. The coordination to mainly 2nd row late-transition metals (Ru, Rh, and Pd) is successfully demonstrated, along with the behavior of their bifunctional character. Application in several catalytic transformations is studied, including various dehydrogenative coupling reactions and the intramolecular hydroamination of aminoalkenes and -alkynes.
| Author | : Ajay Kayal |
| Publisher | : |
| Total Pages | : 574 |
| Release | : 2002 |
| Genre | : |
| ISBN | : |
| Author | : Jason Braun |
| Publisher | : |
| Total Pages | : 0 |
| Release | : 2020 |
| Genre | : |
| ISBN | : |
The idea of 'non-innocent' ligands is that the site of chemical or redox activity on a coordination complex may not be solely limited to the central atom. Ligands may participate either by themselves or in cooperation with a central atom to facilitate electron-transfer and/or chemical reactivity in a more active fashion than in a typical coordination complex. Each of the projects explored in this thesis include the common theme of pyridine-based pincer-type ligands, their coordination to late transition metals and main group elements, and how the reactivity and properties of these complexes involves both the ligand and the ligated element. To do so, a comprehensive investigation of the electronic structure of complexes supported by pincer-type, 'NNN' ligands is also described. Diiminepyridine ligands tend to actively participate in the chemistry of their complexes. Taking advantage of these non-innocent ligands has allowed for the stabilization of unusual oxidation states of transition metal complexes as well as the facilitation of chemical transformations with metals unable to do so using spectator ligands. Pseudo-octahedral iron complexes of these ligands exhibit multiple reversible reductions and are shown to be viable candidates as anolytes for redox flow battery applications. In synthesizing these, a synthetic scheme to prepare these ligands with electron withdrawing groups on the flanking aryl groups was developed, opening up the chemical space for these new ligands in the already well-established field of diiminepyridine ligand chemistry. In addition, bulky analogues engender stabilization of phosphorus complexes in the +1 and +3 oxidations states, not seen before with traditional diiminepyridine ligands. The synthetic route to diarlyamido ligands comprised of flanking quinoline (2,3-benzopyridine) and phenanthridine (3,4-benzoquinoline) donors has also been developed and the coordination of these monoanionic ligands to a variety of late transition metals and main group elements was explored. Several aspects of this ligand can be deemed non-innocent and will be highlighted throughout the course of this thesis. We see an unusual electronic environment of pseudo-octahedral iron complexes of these ligands that exhibit record length charge-transfer excited states and panchromatic absorption. Exchanging the central metal can bring about mixed-valent species upon oxidation evidenced by strong absorption in the near infrared region of the electromagnetic spectrum that significantly depends on metal-ligand orbital overlap.
