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.

No abstract available. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 2001.

The PMR spectra of the two isomers of pyridine-2-aldehyde=2'-pyridyl hydrazone in carbon tetrachloride, dimethyl sulphoxide, and benzene solutions have been studied. Specific associations between PAPHY molecules and solvent molecules have been proposed to account for the observed solvent shifts. Dilution studies have shown that there are PAPHY-PAPHY molecular associations in solution. In the E-isomer these are of the n-donor type involving the lone pair electrons of the ring nitrogen atoms, whereas the Z-isomer association is a dipole-dipole interaction involving the aldehyde ring of different PAPHY molecules. Evidence from long range coupling shows that the uncomplexed E and Z-PAPHY molecules possess a different configuration to the complexed molecules. The chemical shift changes on isomerisation of the E to Z-isomer have been measured and those for the aldehyde ring are consistent with the withdrawal of charge from this ring via the nitrogen atom. Metal complexes of the two isomers of PAPHY have been prepared and their PMR spectra studied. The chemical shifts changes on complex formation have been interpreted in terms of the variation in magnetic anistropy of the ring nitrogen atoms in the ligand molecule and the degree of back donation of d-electrons from the metal atom.

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.

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

"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

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;

Thesis (M.S.)--University of North Texas, Dec., 2007. / Title from title page display. Includes bibliographical references.

Thesis (Ph.D.) -- University of Western Sydney, 2003. / "A thesis submitted as a requirement for admission to the degree of Doctor of Philosophy" Includes bibliographical references (leaves vi, 194-200).

Thesis (D.Sc.)--University of Adelaide, Dept. of Chemistry, 2003. / Includes bibliographical references.