Ruthenium and ruthenium dioxide thin films have shown great promise in various applications, such as thick film resistors, buffer layers for yttrium barium copper oxide (YBCO) superconducting thin films, and as electrodes in ferroelectric memories. Other potential applications in Si based complementary metal oxide semiconductor (CMOS) devices are currently being studied. The search for alternative metal-based gate electrodes as a replacement of poly-Si gates has intensified during the last few years. Metal gates are required to maintain scaling and performance of future CMOS devices. Ru based materials have many desirable properties and are good gate electrode candidates for future metal-oxide-semiconductor (MOS) device applications. Moreover, Ru and RuO2 are promising candidates as diffusion barriers for copper interconnects. In this thesis, the thermal stability and interfacial diffusion and reaction of both Ru and RuO2 thin films on HfO2 gate dielectrics were investigated using Rutherford backscattering spectrometry (RBS), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). An overview of Ru and RuO2/HfO2 interface integrity issues will be presented. In addition, the effects of C ion modification of RuO2 thin films on the physico-chemical and electrical properties are evaluated.

The chemistry of transition metal clusters has been a fast developing area of organometallic research in recent years. Compared to mononuclear metal complexes, polynuclear clusters offer more opportunities to study cooperative effects and electron reservoir properties between contiguous metal centers, in addition to functioning as storehouses for the release of catalytically active small fragments capable of exhibiting heterosite subtrate activation. Theoretically, metal clusters are intermediates between mononuclear complexes and metal surfaces, i.e., they serve as a bridge between molecular and solid-state chemistry. Transition metal clusters are ideal candidates to study M-M interactions stretching from the single bond to the collective metallic behavior found in a three-dimensional network of metal atoms. The reaction between the redox-active diphoshpine ligand bpcd and RU(CO) has been examined under a variety of conditions. The disubstituted cluster Ru3(CO)10(bpcd)(2) has been synthesized and shown to contain a chealating bpcd ligand, on the basis of IR and 31P NMR data. The cluster 2 (chelating isomer) undergoes cluster fragmentation at ambient temperatures in the dark to give the binuclear compound 3 and Ru3(CO)12, with no evidence for the formation of 4. Both 3 and 4 have been isolated and fully characterized in solution by IR and NMR spectroscopy, and the solid-state structure of each new binuclear compound has been established by X-ray diffraction analysis. Independent experiments reveal that dinuclear 3 is converted to 4 by 366 nm light with a quantum efficiency of .0364.

Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: This project entailed the synthesis and characterization of mono- and multi-nuclear rhodium and ruthenium iminopyridyl complexes and their application in the hydroformylation of 1- octene. The multi-nuclear complexes were synthesized in order to investigate whether it could produce catalysts with higher activity than their mononuclear analogues. Four novel iminopyridyl ligands, ranging from mono- to tetra-functional compounds, were synthesized. The synthesis was a two-step process initially involving a Schiff base condensation reaction between 2-pyridinecarboxaldehyde and 4-aminophenol to produce a hydroxy functionalized pyridine-imine. The latter was then subjected to a nucleophilic substitution reaction with an appropriate benzyl bromide derivative to yield the target ligands. All these ligands were isolated in moderate to good yields and characterized using a range of analytical techniques. These ligands, together with the hydroxy functionalized pyridine imine, were then complexed to both Rh(I) and Ru(II) metal precursors, yielding ten novel metal complexes. The characterization of some of the complexes, especially the multi-nuclear complexes, were slightly more difficult due to their low solubility. However, all these complexes could be isolated in good to high yields as stable green-brown (in the case of Rh(I)) and yellow-orange (in the case of Ru(II)) solids. Finally, these complexes were applied as catalyst precursors in the hydroformylation of 1- octene. In the case of the Rh(I) complexes, relatively high activities were observed, with conversions ranging between 50 – 90 % in all cases, when tested at 30 bar, 75 °C and a 0.05 mol% catalyst loading. The activity was found to increase when going from the mono- to the bi-nuclear catalyst. However, solubility in the reaction medium was a major issue for the trinuclear catalyst, as it contributed to the lower activity observed. High chemoselectivity towards aldehydes was observed for all catalysts, which increased with reaction times. During shorter reaction time, linear regioselectivity was also relatively high. This however, decreased with increasing reaction time as the internal octenes formed initially, were converted to branched aldehydes. When the Ru(II) complexes were tested under the same conditions as the Rh(I) complexes, very low activity was observed. Under more stringent conditions (45 bar, 120 °C, 0.5 mol%) the ruthenium catalysts performed relatively well, compared to other complexes in the literature. The same trend in terms of the chemo- and regioselectivity for the Ru(II) complexes were observed. The Rh(I) complexes were far more active than the Ru(II) complexes. / AFRIKAANSE OPSOMMING: Hierdie projek behels die sintese en karakterisering van mono- en multi-kernige rhodium en ruthenium iminopiridiel komplekse en hul toepassing in the hidroformulering van 1-okteen. Die multi-kernige komplekse is gesintetiseer met die doel om vas te stel of hulle katalisatore wat meer aktief is as hul monokernige eweknieë, kan produseer. Vier nuwe iminopiridiel ligande, wat strek vanaf mono- tot tetra-funksionele verbindings, is gesintetiseer. Die sintese was ‘n twee-stap proses wat aanvanklik ‘n Schiff basis kondensasie reaksie tussen 2-piridienaldehied en 4-aminofenol behels, om ‘n fenol gefunksioneerde piridien-imien te vorm. Die laasgenoemde was gevolglik aan ‘n nukleofiliese substitusie reaksie met ‘n gepaste bensiel bromied derivaat onderhewig. Al hierdie ligande is geisoleer in matige tot goeie opbrengste en gekarakteriseer met ‘n reeks analitiese tegnieke. Hierdie ligande, tesame met die fenol gefunksioneerde piridien imien, is dan met Rh(I) en Ru(II) metaal uitgangstowwe gekomplekseer, wat tien nuwe metaal komplekse tot gevolg gehad het. Die karakterisering van sommige van die kompekse, spesifiek die multi-kernige komplekse, was effens moeiliker as gevolg van hul swak oplosbaarheid. Al hierdie komplekse kon egter in goeie tot hoë opbrengste as stabiele groen-bruin (in die geval van Rh(I)) en geel-oranje (in die geval van Ru(II)) vastestowwe geisoleer word. Laastens is die komplekse as katalisator-voorlopers in die hidroformulering van 1-okteen gebruik. In die geval van die Rh(I) komplekse is redelike hoë aktiwiteite waargeneem, met omsettings tussen 50 – 90 % in alle gevalle, wanneer hulle by 30 bar, 75 °C en ‘n katalisator lading van 0.05 mol% getoets is. Die aktiwiteit neem toe vanaf die mono- na die bi-kernige katalisator. Oplosbaarheid in die reaksie medium was egter ‘n probleem vir die tri-kernige katalisator, wat ‘n laer aktiwiteit tot gevolg gehad het. Hoë chemoselektiwiteit na aldehiede is waargeneem vir al die katalisatore en dit neem toe met reaksietyd. Gedurende korter reaksietye was die liniêre regioselektiwiteit ook redelik hoog, maar neem af met toenemende reaksietyd soos die interne okteen wat aanvanklik vorm na vertakte aldehiede omgeskakel word. Toe die Ru(II) komplekse onder dieselfde toestande as die Rh(I) komplekse getoets is, was baie lae aktiwiteite waargeneem. Onder hoër temperatuur en druk (45 bar, 120 °C, 0.5 mol%) toon die ruthenium katalisatore redelik goeie aktiwiteite in vergelyking met ander komplekse wat in die literatuur gerapporteer is. Dieselfde tendense in terme van die chemoen regioselektiwiteit is vir die Ru(II) komplekse waargeneem. Die Rh(I) kompleks was baie meer aktief as die Ru(II) komplekse.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy