In this thesis, C-F bond activation and C-F bond construction under platinum and iridium catalysis is described. Chapter 1 provides a general introduction on the use of transition metal catalysis for the formation and activation of Csp³-F bonds in organofluorine compounds. In Chapter 2, an investigation on the reactivity of allylic fluorides, under platinum and palladium catalysed alkylation conditions, is presented. The relative reactivity of fluoride versus other commonly used leaving groups was compared via internal competition experiments. Fluoride showed a different reactivity profile, when subjected to Pt and Pd catalytic systems. Based on the observed reactivity trend, a Pd-catalysed fluorination reaction of allylic alcohol derivatives was successfully developed, within the group. In Chapter 3, a new iridium catalysed fluorination using branched, E- or Z-linear allylic carbonates is described. The catalyst [Ir(COD)Cl]₂ leads to an unexpected regio- and stereoretentive selectivity, affording fluorinated products not accessible via palladium catalysis. The effect of a fluoride additive on the selectivity of the Ir-catalysed alkylation reaction is also presented. A highly efficient ¹⁸F-fluorination variant for this new catalytic transformation is reported. Chapter 4 gives full experimental procedures and characterisation data for all compounds.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / Chemistry / Doctoral / Doctor of Philosophy

This dissertation describes a study of the electronic structure of some selected cyclopentadienyl metal olefin, (mu)-alkylidene, and carbonyl complexes. While most studies of this type are largely theoretical in nature, this work relies on the experimental observations which result from the application of photoelectron spectroscopy to the measurements of the important molecular energies of these compounds. The first part of the discussion is a study of metal-olefin bonding in the CpM(CO)₂L (L = C₂H₄, C₃H₆) compounds. Of particular interest are the observed changes in ionization energies of the olefin (pi) orbital upon coordination. These results also allow a comparison of the coordination of CO and C₂H₄. The valence ionizations of μ-CH₂-[(C₅H₄CH₃)Mn(CO)₂]₂ are also presented. This example of the increasingly important μ-alkylidene complexes provides evidence of a 3C-6e configuration with a net Mn-Mn single bond. The final chapter describes a study of the valence electronic structure of the CpM(CO)₂ (M = Co, Rh; Cp = η⁵-C₅H₅⁻) and η⁵-C₅(CH₃)₅⁻ ) system. This group of four closely related molecules demonstrates how photoelectron spectroscopy can be used to monitor the electronic effects of specific chemical modifications. The intent throughout is to not only present a detailed analysis of the specific compounds chosen for this study, but to also further demonstrate the applicability of photoelectron spectroscopy to a broad spectrum of problems concerning the structural and electronic make-up of organometallic molecules.

Principles involving the electronic structure of group VI metal-metal multiple bonded complexes are examined in order to provide insights into the intramolecular and intermolecular interactions of these systems. Examination of chromium, molybdenum and tungsten tetracarboxylate thin films by ultraviolet photoelectron spectroscopy has provided the first experimental evidence for the location of the σ ionization in dimolybdenum tetracarboxylate quadruple bonded complexes. These compounds have significant intermolecular interactions as thin films which destabilizes ionization of the valence σ state, allowing it to be experimentally observed. This is supported by the observed destabilization of the σ ionization feature of the ditungsten analogue in going to the thin film. The Cr₂(O₂CCH₃)₄ comparison shows a destabilization of the leading predominantly metal ionizations consistent with the broad range of M-M bond lengths observed for Cr₂ complexes. The Group VI M₂(mhp)₄ and M₂(chp)₄ [mhp=6-methyl-2-oxo-pyridine and chp=6-chloro-2-oxo-pyridine] complexes are also examined. The geometric constraints imposed on the compounds by the ligand effectively block intermolecular interaction axial to the metal-metal bond in the solid state. Comparison of the two ligand spectra, Hmhp and Hchp, has provided a unique opportunity to assign ionizations previously attributed to the keto form of the Hmhp tautomers. The spectra of the complexes exhibit minimal relative shifting of ionization features in going to the thin films because of this constraint. A band previously believed to be due to spin orbit coupling is assigned to the σ ionization in the ditungsten complex. The overall ionization band profiles of the two series correlate well, metal by metal, with the expected shifting due to substitution of the more electronegative chlorine atoms for a methyl group. The synthesis and characterization of Mo₂(N-t-butyl-acetamide)₄, the first tetraamidodimetal compound without large rings with delocalized pi structure, is described. The single crystal X-ray structure is presented, revealing the novel (one of three examples) cis configuration of the MoN₂O₂ ligand set. The Mo-Mo bond length of 2.063 Å is one of the shortest seen to date. A preliminary gas phase He I valence spectrum is reported.

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No description available.

The synthesis and characterization of pyridinyl &alpha / -diimine Pd(II) complexes having a functionalized hydrocarbon attached to the imino nitrogen was performed. The catalytic activity of these complexes were then evaluated in the polymerization of ethylene and in the Heck coupling reaction of methyl acrylate with iodobenzene.<br /> <br /> Unconjugated &beta / -diimine complexes of palladium were also synthesized and their activities towards ethylene polymerization and the Heck coupling of methyl acrylate and iodobenzene also evaluated and compared to that of the &alpha / -diimine complexes. Three of the &alpha / -diimine complexes synthesized showed activity towards ethylene polymerization, these being the complexes bearing the allyl, styrene and phenol functionalities. &omega / -Carboxylato complexes which were also synthesized showed no activity towards ethylene polymerization.<br /> <br /> The polymer produced was found to be high density linear polyethylene with an average PDI of 2.54 with Mn values ranging between 3.42 and 6.90 x 10-5 and Mw values ranging between 6.05 and 17.6 x 10-5.<br /> <br /> The complexes bearing the allyl, styrene and phenol functionalities, as well as the &omega / -carboxylato complexes active in the Heck coupling reactions of methyl acrylate with iodobenzene. None of the unconjugated &beta / -diimine complexes prepared showed any activity towards ethylene polymerization even at high Al/Pd ratios. The activity of these complexes towards the Heck arylation reaction was comparable to that of the &alpha / -diimine complexes showing similar activities.

Little attention has been given to the formation of the putative PdL2 species required for Pd-catalyzed cross-coupling reactions. Active species are generally difficult to store due to air-sensitivity and are therefore formed in situ at unknown rates and in unknown yields via a variety of palladium precatalysts. Commonly employed Pd(0) and Pd(II) precatalysts are often relatively ineffective because they generate only low concentrations of the bis(phosphine) species PdL2 under most reaction conditions. This thesis describes the use of the easily synthesized and easily handled Pd(η3-1-Ph-C3H4)(η5-C5H5) (I) as a superior precursor than any other documented system for the in situ formation of PdL2. Rapid and quantitative formation of active catalyst solutions allow us to demonstrate that I is also the best precatalyst known for PdL2-catalyzed crosscoupling reactions. We discuss the Suzuki-Miyaura reaction of 4-bromoanisole with phenylboronic acid and demonstrate that, under mild reaction conditions, higher initial rates and higher conversions with I can be obtained compared with other common precatalysts (Pd(OAc)2, Pd(PPh3)4, Pd2dba3, etc.) containing a variety of phosphine ligands. This methodology has also been extended to other cross-coupling reactions, as we demonstrate that higher initial rates and higher conversions with I can be obtained for a variety of Mizoroki-Heck arylations and Buchwald-Hartwig aminations. / Thesis (Ph.D, Chemistry) -- Queen's University, 2013-06-25 11:53:06.75