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Rotational Spectroscopy and Structures of Organometallic CompoundsKarunatilaka, Chandana January 2007 (has links)
High-resolution pulsed beam Fourier Transform Microwave Spectroscopy (PBFTMS) technique has been used to investigate the rotational spectra, molecular structures and electronic charge distribution of organometallic and organic molecules. The thesis reports high-resolution rotational spectral findings for nine different asymmetric-top molecules in the singlet electronic ground state including: Cyclopentadienyltungstentricarbonylhydride, Bis-(cyclopentadienyl)tungstendihydride, Tetracarbonylethyleneosmium, two substituted Ferrocenes and an organic keto-enol tautomeric system, Z-2-Hydroxypyridine and 2-Pyridone. Moreover, gas-phase rotational constants and distortion constants have also been reported for an excited vibrational state of Cyclopentadienylnickelnitrosyl complex using a high-resolution Fourier Transform Spectrometer (FTS) system at Kitt Peak Arizona, (KPNO). Preliminary microwave results for a fluxional molecule, Cyclopentadienyliridiumdicarbonyl are also presented in this work. Extensive Density Functional Theory (DFT) calculations have been performed in conjunction with the experiments to provide additional insight toward further understanding the equilibrium structures, structural isomers and electric field distributions of these molecules. These calculations were not only helpful in predicting the preliminary structure and rotational constants of the molecules of interest, but also advantageous in analyzing the observed spectra.
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N-heterocyclic carbene-iron(II) complexes : chemistry and application as transfer hydrogenation catalysts.Ikhile, Monisola Itohan. 27 November 2013 (has links)
In the last decade N-heterocyclic carbene (NHC) ligands have become important in organometallic
chemistry and homogeneous catalysis, rivalling the well established phosphines. Most of the
current attention to date has focused on the NHC complexes of the platinum group metals (rhodium,
palladium and nickel) plus ruthenium based system, but the chemistry of NHC systems of iron
which is relatively inexpensive and environmentally friendlier is considerably less developed.
Thus, this project involves the design, synthesis, characterization and application in catalytic
transfer hydrogenation of NHC ligands and their iron(II) complexes.
The motivation for the choice of NHC as a ligand stems from the ability to systematically tune the
ligand both electronically and sterically in addition to the stability and robustness of the ligand to
stabilize metal centres in various environments. In this research imidazolium based NHCs are
generated. Thus, three different series of imidazolium salts were synthesized and their iron(II)
complexes was obtained. All the compounds were characterized by spectroscopic and
crystallographic methods. These are: (a) 1,3-dialkylimidazolium salts (b) 1,3-diarylimidazolium
salts and (c) ferrocenylimidazolium salts bearing methyl and phenyl spacers between the ferrocenyl
and the imidazolium moieties. A total of 20 novel compounds were synthesized and are reported in this thesis. Furthermore, the application of the new compounds as transfer hydrogenation catalysts was
investigated using 17 saturated and unsaturated ketones as substrates, in the presence of KOH as the
base and 2-propanol as the hydrogen source. The dialkylated NHC iron(II) complexes showed
excellent yields, and TON values of up to 200 were achieved under the optimized reaction
conditions. Without complexation with iron, the 1,3-diarylimidazolium and ferrocenylimidazolium
series of salts were also found to be active catalysts for the transfer hydrogenation reaction of
ketones in alcoholic media. In the case of ferrocenylimidazolium salts a TON value up to 1880 was
achieved. Notably, two of the unsaturated ketones were successfully converted at a high yield with
a high selectivity to the corresponding saturated ketones only.
In addition, the stability of NHC ligands to moisture was investigated, since an understanding of the
stability of various deprotonated NHC-based imidazolium cations to attack by moisture resulting in
hydrolysis products is very important to understanding the coordination chemistry of the ligands on
to metal centres. Four novel ionic diamino aldehyde compounds were obtained by moisture attack
on saturated NHC ligands. The route to the formation of the hydrolysed compounds is formulated
to occur via an imidazolinium ring opening process. On the other hand the unsaturated counterparts
were more stable towards hydrolysis yielding adducts with the iron(II) precursors.
Finally, the electrochemical properties of the ferrocenylimidazolium salts were investigated using
cyclic voltametry. By comparing the relative shifts in the formal electrode potentials of the
ferrocene/ferrocenium coupled with the ferrocenylimidazolium salts, it was easy to evaluate the
influence of the substituents on the carbene containing imidazolium moiety on the electrochemical
properties of the iron centres. The formal electrode potential of the ferrocenylimidazolium salts
shifted to higher positive potentials as compared to ferrocene, indicating a high electron
withdrawing effect of the imidazolium salts. This makes the metal centres more vulnerable to
attack by nucleophiles. The electrochemical studies have enabled a structure-activity correlation to
be drawn for the various ferrocenylimidazolium salts. / Thesis (Ph.D.)-University of KwaZulu-Natal, Westville, 2011.
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Titanium imido compounds with pendant arm amidinate ligandsBoyd, Catherine Louise January 2004 (has links)
This Thesis describes the synthesis and characterisation of titanium imido compounds supported by pendant arm functionalised amidinate ligands. Reactivity studies of cyclopentadienyl amidinate-imido compounds with CO2 are presented. Chapter 1 introduces transition metal imido chemistry, with a particular emphasis on imido complexes of titanium. Chapter 2 describes recent developments in the chemistry of functionalised amidinate ligands. The synthesis and characterisation of new titanium imido compounds with pendant amine functionalised amidinate ligands is described. The preparation of an amidinate ligand with a pendant propyl arm is reported. Reactions of a selection of these complexes with small molecules are presented. Chapter 3 reviews recent developments in the chemistry of cyclopentadienyl amidinate-imido compounds. The preparation of cyclopentadienyl-supported titanium imido compounds bearing pendant arm amidinate ligands is described andthereactionsofthesecompoundswithCC>2arediscussed. Kineticanddensity functional theory studies of these reactions are presented. Chapter 4 describes the synthesis and characterisation of alkyl and aryloxide titanium amidinate-imido compounds. The preparation of cationic derivatives is also described and reactions of these cationic derivatives with small molecules are discussed. Chapter 5 presents full experimental procedures for all of the syntheses and reactivity studies outlined in Chapters 2 to 4. Chapter 6 contains characterising data for all of the new compounds reported. Appendices A - K contain tables of selected crystallographic data for all new crystallographically characterised complexes described in this Thesis. Appendices L - O contain kinetics data relating to work discussed in Chapter 3.
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A study of transition metal complexes / Paul Andrew Humphrey.Humphrey, Paul Andrew January 1990 (has links)
Includes bibliographical references. / 249 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physical and Inorganic Chemistry, 1991
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Molecular wires : syntheses, electrochemistry and properties of metal complexes containing carbon chains / by Mark Edward Smith.Smith, Mark Edward, 1975- January 2002 (has links)
"September 2002" / Includes as appendix: a list of publications by the author arising from this work; and, copies of some published journal articles / Includes bibliographical references. / [12], 209 leaves, [35] pages : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Describes the synthesis, properties and reactions of transition metal complexes containing poly-ynyl ligands / Thesis (Ph.D.)--University of Adelaide, Dept. of Chemistry, 2002
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Magnetization-steps spectroscopy in dilute magnetic semiconductors and in molecular magnetism /Liu, Mingde. January 1998 (has links)
Thesis (Ph.D.)--Tufts University, 1998 . / Adviser: Yaacov Shapira. Submitted to the Dept. of Physics. Includes bibliographical references. Access restricted to members of the Tufts University community. Also available via the World Wide Web;
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A computational investigation of the photophysical, electronic and bonding properties of exciplex-forming Van Der Waals SystemSinha, Pankaj. Omary, Mohammad A., January 2007 (has links)
Thesis (M.S.)--University of North Texas, Dec., 2007. / Title from title page display. Includes bibliographical references.
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Molecular wires : syntheses, electrochemistry and properties of metal complexes containing carbon chains /Smith, Mark Edward, January 2002 (has links) (PDF)
Thesis (Ph.D.)--University of Adelaide, Dept. of Chemistry, 2002. / "September 2002" Includes as appendix: a list of publications by the author arising from this work; and, copies of some published journal articles. Includes bibliographical references.
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Hydrogen atom transfer reactions of iron and cobalt tris alpha-diimines : a study of intrinsic and thermodynamic effects /Mader, Elizabeth Anne. January 2007 (has links)
Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (p. 169-185).
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Tridentate, dianionic ligands for alkane functionalization with platinum(II) and oxidation of iridium(III) hydrides with dioxygen /Williams, Dara Bridget. January 2007 (has links)
Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (leaves 119-130).
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