When syn-benzaldoxime was reacted with carbon monoxide containing about 0.04 volume percent of hydrogen and dicobalt octacarbonyl in benzene solution at elevated temperatures and pressures the following compounds were produced; sym-dibenzylurea (35%), monobenzylurea (10%) and benzaldehyde (10%). Also isolated were 15% yields of two unidentified components referred to as compounds A and B. When benzophenone oxime was subjected to the same reaction conditions the major product was 3-phenylphthalimidine (75%). Also isolated was a 5% yield of an unidentified component called compound B. It was demonstrated that under the reaction conditions used considerable amounts of dicobalt octacarbonyl are needed for successful reaction. When the octacarbonyl was present in only catalytic amounts the course of the observed reaction was greatly affected and the major isolated product was benzophenone (70%). Small amounts of 3-phenylphthalimidine and of the original oxime were also isolated. When the 0-methyl ether of benzophenone oxime was reacted the only product isolated was 3-phenylphthalimidine in 75% yield. Reaction pressures corrected to constant temperature are plotted against reaction time for each substrate and the results discussed. A new method of synthesizing the 0-methyl ether of benzophenone oxime (using 0-methyl hydroxylamine), and a dichromate-acetic acid oxidation of sym-dibenzylurea giving a high yield of dibenzoylurea are described. A platinum oxide in acetic acid reduction of 3-phenylphthalimidine which reduced both benzene rings but left the lactam group intact is also described. Infrared spectra are included for all compounds obtained. / Science, Faculty of / Chemistry, Department of / Graduate

<p> Dicobalt octacarbonyl reacts with a wide variety of molecules containing trichloromethyl functionalities to yield carbynyl tricobalt nonacarbonyl clusters of the general formula R-CCo 3 (CO) 9 . While these clusters have been shown to undergo many reactions, mechanistic studies on these systems are sparse. In particular, their rather facile decarbonylation processes are not well understood. </p> <p> Complexes of the type Ar-CO-CCo 3 (CO)9 readily lose CO to produce the corresponding Ar-CCo 3 (C0) 9 clusters but the origin of the carbon monoxide extruded was not known . Speculation had focussed on two possibilities: firstly, direct elimination of the ketonic carbonyl - perhaps via radical intermediates - and, secondly, via initial loss of a cobalt carbonyl ligand (to produce a 16-electron cobalt vertex) with subsequent migration of the original ketonic group onto the coordinatively unsaturated cobalt center. These two mechanistic possibilities are differentiable by labelling either the cobalt carbonyl sites or the ketonic position with carbon-13 and then examining the decarbonylated product to locate the isotopically enriched positions by 13c NMR spectroscopy. It is shown that the carbon monoxide initially eliminated is a cobalt carbonyl and the ketonic CO migrates from its apical position onto a cobalt atom. </p> <p> A second project involves the synthesis and characterization of a cobalt cluster derived from the reaction of dicobalt octacarbonyl with the insecticide DDT . This cluster contains the bis(4-chlorophenyl)methylcarbynyl capping group which is so bulky that it has the potential to stop the rotation of the carbynyl ligand and also prevent carbonyl exchange on the metal triangle. The DDT-tricobalt cluster was characterized by X-ray crystallography. The compound crystallizes in the space group P21/n: the monoclinic cell has dimensions a = 13.083 A, b = 14.222 A, c = 14.165 A, B = 95.871 degrees and Z = 4. The molecule adopts almost Cs symmetry except that the phenyl rings are twisted slightly so as to destroy the potential mirror plane. At low temperature, the cobalt carbonyl ligands are non-equivalent on the NMR time-scale and the possible causes for this behaviour are discussed. </p> / Thesis / Master of Science (MSc)

During recent years the demand for nanoscale materials with tailor-made functional properties as bulk species, is continuously and progressively rising for such fields as e.g. micro- and nano-electronics, plasmonics, spintronics, bio-technology, bio-sensing and life sciences. Preserving and / or improving properties of functional materials with their simultaneous size reduction and high-resolution site-specific positioning is indeed very challenging, for both conductors and insulators. One of the advanced nanoprototyping methods that can be utilized for this purpose is the Electron-Beam-Induced Deposition, or shortly EBID. This process is based on a local decomposition by a focused electron beam of a precursor gas molecules adsorbed on the sample’s surface. The beauty of this method is that it gives a unique possibility of rapid creation of site-specific nanoscale 3D structures of precise shape in a single operation. It’s an additive process that can be easily combined with other patterns. However, besides all the benefits, EBID has some constraints, in particular low purity of the deposited materials, due to the organometallic nature of the used precursors. Chemical composition of EBID patterns is strongly dependent on the chosen gas chemistry, the substrate, many deposition parameters and post-treatment processes applied to the deposited structures. In our research we focused on deposition of Co, Au, SiO2, C, W and Pt, their purification and shape control. And this thesis presents an overview of our accomplishments in this field. Depending on the gas chemistry of interest, three major purification approaches of EBID-grown materials were tested out: - Post-deposition annealing: in air and in the controlled atmosphere, - Deposition onto a preheated substrate, - Deposition in the presence of reactive gases. As a result, a dramatic purity improvement was observed and a significant advancement was achieved in creation of high-purity gold, cobalt and silicon dioxide nanoscale structures. In particular: 1)   For the Me2Au(acac) precursor, we developed a nanofabrication routine combining application of wetting buffer layers, fine tuning of EBID parameters and subsequent post-annealing step, which led to formation of high-purity planar and high aspect ratio periodic Au nanopatterns. We also describe the adopted and gently adjusted wet etching method of undesirable buffer layer removal, required in some cases for the further device application. 2)   For the Co2(CO)8 precursor, in-situ seeded growth in conjunction with EBID at the elevated substrate temperature resulted in a deposition of pure nanocrystalline Co with magnetic and transport properties close to the bulk material. 3)   For the tetraethyl orthosilicate precursor, or shortly TEOS, assisting of the deposition process with the additional oxygen supply led to the EBID of carbon-free amorphous insulating Si-oxide, with the absorption and refraction properties comparable to those for fused silica. Several applications of EBID nanopatterns are also discussed. / <p>QC 20131028</p>

<p>Transition metals have played an important role in synthetic organic chemistry for more than a century, and offer catalytic transformations that would have been impossible with classical chemistry. One of the most useful and versatile of the transition metals is palladium, which over the years has catalyzed many important carbon-carbon forming reactions. Popular cross-coupling reactions such as the Suzuki, Stille and the Heck reaction are all catalyzed by palladium, or more correctly, by palladium in its ground state, Pd(0). </p><p>Recently, interest in palladium(II)-catalyzed transformations has started to grow, partly due to the development of the vinylic substitution reaction, commonly called the oxidative Heck reaction, presented in this thesis. This Pd(II)-catalyzed, ligand-modulated reaction occurs under air at room temperature, and for the first time a general protocol employing a wide range of olefins and arylboronic acids was obtained. Ligand screening showed that the bidentate nitrogen ligand, 2,9-dimethyl-1,10-phenanthroline (dmphen), was the most suitable ligand. Dmphen is believed to facilitate regeneration of active Pd(II), increase catalytic stability and improve the regioselectivity in the reaction. A mechanistic investigation was conducted using electrospray ionization mass spectrometry (ESI-MS), making it possible to observe cationic intermediates in a productive oxidative Heck arylation. The results obtained are in agreement with the previously proposed catalytic cycle.</p><p>The emerging discipline of high-speed synthesis is making contributions to society’s growing demand for new chemical entities. This inspired the development of two ultrafast, microwave-accelerated carbonylation reactions with dicobalt octacarbonyl acting both as an in situ carbon monoxide supplier and reaction mediator. A wide range of symmetrical benzophenones was produced in only 6 to 10 s, using aryl iodides as the substrate. The second carbonylation reaction provided symmetrical and unsymmetrical ureas in process times ranging from 10 s to 40 minutes using primary and secondary amines.</p>

Transition metals have played an important role in synthetic organic chemistry for more than a century, and offer catalytic transformations that would have been impossible with classical chemistry. One of the most useful and versatile of the transition metals is palladium, which over the years has catalyzed many important carbon-carbon forming reactions. Popular cross-coupling reactions such as the Suzuki, Stille and the Heck reaction are all catalyzed by palladium, or more correctly, by palladium in its ground state, Pd(0). Recently, interest in palladium(II)-catalyzed transformations has started to grow, partly due to the development of the vinylic substitution reaction, commonly called the oxidative Heck reaction, presented in this thesis. This Pd(II)-catalyzed, ligand-modulated reaction occurs under air at room temperature, and for the first time a general protocol employing a wide range of olefins and arylboronic acids was obtained. Ligand screening showed that the bidentate nitrogen ligand, 2,9-dimethyl-1,10-phenanthroline (dmphen), was the most suitable ligand. Dmphen is believed to facilitate regeneration of active Pd(II), increase catalytic stability and improve the regioselectivity in the reaction. A mechanistic investigation was conducted using electrospray ionization mass spectrometry (ESI-MS), making it possible to observe cationic intermediates in a productive oxidative Heck arylation. The results obtained are in agreement with the previously proposed catalytic cycle. The emerging discipline of high-speed synthesis is making contributions to society’s growing demand for new chemical entities. This inspired the development of two ultrafast, microwave-accelerated carbonylation reactions with dicobalt octacarbonyl acting both as an in situ carbon monoxide supplier and reaction mediator. A wide range of symmetrical benzophenones was produced in only 6 to 10 s, using aryl iodides as the substrate. The second carbonylation reaction provided symmetrical and unsymmetrical ureas in process times ranging from 10 s to 40 minutes using primary and secondary amines.