Formation of carbon–fluorine and carbon–fluoroalkyl bonds via transition metal complexes represents an efficient synthetic route towards a wide array of valuable fluorinated organic compounds and fluorinated metallacycles offer a potentially green and atom economical pathway towards these functionalized fluorocarbons. This thesis is focused on cycloaddition reactions of Ni=CF2 complexes with fluoroalkenes (FAs) and acetylenes. Cycloaddition reactions of the FAs vinylidene fluoride (CF2=CH2) and perfluoro(methyl vinyl ether) [CF2=CF(OCF3)] with the electron-rich Ni(0) fluorocarbene, Ni=CF2[P(OMe)3](dppe) affords stable metallacyclobutane complexes, likely through a 1,4-diradical mechanism previously investigated for analogous reactions using computational chemistry. With CF2=CHF (TrFE), however, the observed products are the C3 alkene E-CHF=CF(CF3) and the metallacyclopentane complex, Ni(C4H2F6)(dppe), derived from oxidative coupling of two additional equivalents of TrFE. It is proposed that the instability of the initially formed metallacyclobutane gives rise to a 2,1-F shift, yielding the C3 alkene complex. Reaction of the latter with excess TrFE then liberates the C3 alkene, forming the TrFE alkene complex followed by the observed metallacyclopentane product. In the reaction of 1a with chlorotrifluoroethylene (CF2=CFCl) a single regioisomer of the metallacyclobutane is observed, but reacts further in THF solvent via α-Cl migration to Ni, affording the tetrafluoroallyl complex, NiCl(CF2CF=CFH), in which one F has been replaced by a hydrogen. Finally, reaction of 1a with hexafluoropropene [CF2=CF(CF3), HFP] takes an unprecedented turn, affording the Ni trifluoromethyl perfluoroalkenyl complex from formal transfer of one F from HFP to the Ni=CF2 moiety. The capability of 1a to perform cycloaddition with a broader substrate scope was investigating by reacting it with terminal aryl-acetylenes of varying electronic parameters. Reaction of 1a with 1.5 equivalents of 4-R-phenylacetylene afforded the expected difluorometallacyclobutenes (R = H, Cl, tBu). Further observation revealed a second acetylene insertion to yield a nickelacyclohexadiene in the first example of a 4- to 6-membered ring expansion of perfluorometallacycles. The six-membered metallacycle then undergoes reductive elimination to furnish a difluorocyclopentadiene. The electronic parameters of the aryl-acetylene substrate play a dramatic role in the selectivity of product formation. The more electron-donating substrates 4-tert-butylphenylacetylene and 1-hexyne stabilize the metallacyclobutene, while the electron-withdrawing 4-chlorophenylacetylene affords a more reactive metallacyclobutene making it more prone to the second acetylene insertion. Phenylacetylene represented a middle-ground between the two systems and proved effective for further characterization studies. The electronic effect of the surrounding ancillary ligand system was also studied by substituting dppe in 1a for P(OMe)3 and dipe to give analogous Ni(0) difluorocarbene complexes 1b and 1c (dipe = 1,2-bis(diisobutylphosphino)ethane). The -acidic phosphite ligands in 1b gave exclusively nickelacyclohexadiene and difluorinated cyclopentadiene due to a reactive metallacyclobutene, whereas the more electron rich 1c formed the metallacyclobutene product almost exclusively. The results presented here will allow for future investigations of fluorinated metallacycle reactivity, increasing our ability to prepare value-added fluorocarbon products for pharma, agrochemicals, and polymer applications.

This thesis is a study of solid halogenated organic compounds by Nuclear Magnetic Resonance Spectroscopy (NMR) in an attempt to extract previously inaccessible information. The first part of the thesis is concerned with three fluorinated steroids, studied by observing (^1)H, (^13)C and (^19)F nuclei. A number of experimental techniques are employed to verify solution-state and solid-state spectral assignments, and spectral anomalies are discussed. Both proton-coupled and proton-decoupled (^19)F solid-state spectra, recorded using specially designed spectrometer hardware, are presented. The huge gain in resolution afforded by the implementation of proton decoupling allows static and MAS spectra to yield previously inaccessible information pertaining to various NMR parameters of the fluorine nuclei. Advantages of (^1)H→(^19)F cross-polarisation experiments over single-pulse experiments are explained and rotational resonance, dipolar dephasing, T(_1), measurement and spin-exchange experiments are presented from which information regarding phenomena such as spin diffusion and polymorphism is gleaned. The second part of the thesis focusses on the topic of residual dipolar coupling, the transfer of quadrupolar effects to spin-1/2 nuclei via dipolar coupling and/or anisotropy m indhect coupling. Unexpected, field-dependent, multiplicities for signals in spectra of spin-1/2 nuclei are observed, which can be used to evaluate certain fundamental NMR parameters including the quadrupolar coupling constant and, m favourable cases, anisotropy in indirect coupling. The phenomenon is comprehensively studied for the (^13)C, (^35,37)Cl and (^13)C, (^79,81)Br spin-pairs in a range of solid halogenated compounds. Coupling to more than one halogen nucleus and long- range (non-bonded) coupling are considered. First-order perturbation, inverse first- order and "exact" theories, that allow the multiplet line positions to be predicted, are introduced and their results are subsequently compared to the experimentally observed the positions. Rapid molecular motion is shown to negate the effects of residual dipolar coupling and the phenomenon is analysed with the aid of NQR measurements.

Photovoltaic cells and fluorescence sensing are two important areas of research in chemistry. The combination of photon-activated electron donors with electron acceptors provides a strong platform for the study of optical devices. A series of four oligothiophene-ruthenium complexes has been synthesized. Variation in oligothiophene length and bipyridine substitution allowed comparison of these variables on electronic properties. The longer oligothiophenes display lower energy absorption and emission compared to the shorter ones. Aromatic conjugation appears more complete with para-, rather than meta-, substitution. Oligothiophenes and Ru(bpy)32+ are highly fluorescent individually, but fluorescence is quenched when connected. Bonds of carbon to fluorine are among the strongest single bonds. Single bonds between carbon and hydrogen are also very strong and are ubiquitous. The ability to manipulate these bonds is of great interest to chemists. Two tungsten metal complexes, [6 (perfluorophenyl)bipyridyl] tetracarbonyltungsten and [6-(phenyl)bipyridyl]tetracarbonyltungsten, were prepared for mechanistic C-F and C-H bond activation studies, respectively. These compounds were synthesized through Stille and Suzuki coupling of commercial reagents. Ligands were then bound to tungsten to form the tetracarbonyl complexes.

No description available.

Poly- and perfluoroalkyl substances (PFAS) are ubiquitous contaminants across the globe, can bioaccumulate in aquatic taxa, and potentially biomagnify in food webs. Consequently, research examining the influence of PFAS on wildlife is warranted. Amphibians are sensitive to contaminants such as PFAS because of their porous skin and associations with aquatic habitats where contaminants accumulate. Because PFAS tend to bioaccumulate and can adversely affect the endocrine system, there is a need to examine uptake rates to inform ecotoxicology studies, as well as a need to examine sublethal effects. To address these knowledge gaps I conducted two experiments. First, I exposed larval northern leopard frogs (<i>Rana pipiens</i>), American toads (<i>Anaxyrus americanus</i>), and eastern tiger salamanders (<i>Ambystoma tigrinum</i>) to PFAS chemicals perfluorooctanoic acid (PFOA) or perfluorooctane sulfonate (PFOS) at concentrations of 10 or 1000 ppb for 10 days and sampled them every 48 hours during the exposure period. In the next experiment, I examined the effects of PFAS exposure via contaminated substrate on the survival and growth of post metamorphic amphibians of the same species. I found that, for all species, body burdens often reached steady state within 48 to 96 h of exposure. Steady-state body burdens of PFOA ranged from 3,819–16,481 ng/g dry weight among treatments and species (corresponding BCFs of 0.5 to 2.5), while PFOS body burdens ranged from 6,955–489,958 ng/g dry weight (corresponding BCFs of 47–259) among treatments and species. These data suggest that steady state is rapidly reached in larval amphibians exposed to PFAS, particularly regarding PFOS. This reflects a high potential for trophic transfer of PFAS within food webs because amphibians are often low in trophic position and are important prey for many aquatic and terrestrial species. In post-metamorphic amphibians, there was no influence of PFAS on survival or mass. However, significant effects on snout-vent length were observed in all species, and body condition differences were observed for two of my species. I found that all leopard frogs increased in scaled mass index (SMI) when exposed to a PFAS treatment, indicating an increased body condition. Toads exhibited a more variable SMI pattern across treatments, with no outstanding trends, and tiger salamanders did not differ significantly across treatments. These data suggest that sublethal effects vary greatly depending on the species, possibly due to life history traits. Future research examining biomagnification potential is warranted to determine the influence of PFAS on food webs. Additionally, there is a need to determine the physiological mechanisms underlying the observed effects of PFAS exposure.<br>