Transition metal containing zeolites (zeolite A and ZSM-5) were prepared by addition of various transition metal containing substrates to zeolite synthesis gels. Crystal growth data were recorded in order to determine the influence of the transition metal species on the rate of crystal growth. X-ray diffraction, oxygen adsorption, FTIR and SEM were utilized to evaluate crystal purity. X-ray photoelectron spectroscopy (XPS), chemical analysis and electron microprobe analysis were performed in order to ascertain the position (intrazeolitic versus surface) and homogeneity of the transition metal. It was concluded that intrazeolitic transition metals were produced by the novel procedure presented in this work. 1-Hexene hydroformylation by rhodium zeolite A showed intrazeolitic rhodium to migrate to the external surface of the zeolite. However, in the presence of a solution and surface rhodium poison, intrazeolitic rhodium was found to hydroformylate 1-hexene exclusively to heptanal. Ruthenium containing zeolite A was evaluated under CO-hydrogenation conditions. No migration of intrazeolitic ruthenium to the external surface of the zeolite was observed over the course of the reaction. The product distribution obtained for this catalyst did not follow a log normal behavior. Also, loss of zeolite crystallinity was observed following the reaction. Cobalt ZSM-5 was evaluated under CO-hydrogenation conditions. No migration of cobalt to the external surface of the zeolite occurred. XPS analysis of the catalyst following various stages of the reaction indicated that intrazeolitic cobalt was not reduced to the zero valent state. Consequently, the non-zero valent cobalt was not capable of hydrogenating carbon monoxide. / Ph. D.

published_or_final_version / abstract / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / Chemistry / Doctoral / Doctor of Philosophy

The electronic structure factors that control Si-H and Ge-H bond activation by transition metals are investigated by means of photoelectron spectroscopy. Molecular orbital calculations are also used to gain additional insight into the orbital interactions involved in bond activation. The complexes studied have the general molecular formula (η⁵-C₅R'₅)Mn(CO)(L)HER₃, where R' is H or CH₃, L is CO or PMe₃, E is Si or Ge and R is Ph or Cl. These compounds are interesting models for catalysts in industrial processes like hydrosilation. The compounds display different stages of interaction and "activation" of the E-H bonds with the metal. One purpose is to measure the degree of Mn, Si, H 3-center-2-electron bonding in these complexes. The three-center interaction can be tuned by changing the substituents on Si, methylating the cyclopentadienyl ring, changing the ligand environment around the metal and substituting Si with Ge. The degree of activation is measured by observing the shifts in the metal and ligand ionizations relative to starting materials and free ligand in the photoelectron spectrum. Changing the substituent on Si extensively changes the degree of activation. Photoelectron spectral studies on (η⁵-C₅H₅)Mn(CO)₂HSiPh₃ show this to be a Mn(I) system. Progressive methylation of the cyclopentadienyl ring increases the electron richness at the metal center with no substantial effect on the degree of activation. Substitution on the metal (PMe₃ for CO) is less able to control the electronic structure factors of activation than the substitution on the Si atom. The magnitude of Ge-H bond activation is found to be of the same order as the Si-H bond activation for analogous compounds as found by studying (η⁵-C₅H₅)Mn(CO)₂HGePh₃, (η⁵-CH₃C₅H₄)Mn(CO)₂HGePh₃ and (η⁵- C₅(CH₃)₅)Mn(CO)₂HGePh₃ complexes by photoelectron spectroscopy. The photoelectron spectra of CpFe(CO)₂SiCl₃ and CpFe(CO)₂SiMe₃ were measured to study the electron charge shift from the metal to the ligand in these complexes as compared to CpMn(CO)₂HSiR₃ complexes. The photoelectron spectroscopic studies include numerous perturbations of the ligand and metal center to observe the extent of bond interaction and remain one of the best techniques to detect activation products.

Paraffin activation has practical implications in the replacement of current petrochemical feedstocks (olefins), by utilizing economical and easily accessible alkanes, which may result in more efficient strategies for fine chemical synthesis and the proficient use of energy. However, the chemical inertness of paraffins limits their conversion to more valuable products. Several pincer chelate complexes are utilized in stoichiometric and catalytic C–H activation. These pincer ligands have attained much interest in that they are part of a system, which displays high stability, activity and variability. In this study four aminodiphosphine (PNP) pincer ligands were successfully synthesized and characterized by NMR, IR and HRMS. To investigate the steric effects on the metal center, four different functional groups on the nitrogen atom were used, a cyclic ring (cyclohexyl (3.1)) branched chain (iso-propyl (3.2)); straight chain (pentyl (3.3)); and aromatic ring (benzyl (3.4)). The ligands were successfully complexed to the transition metals iridium and cobalt and characterized by elemental analyses, IR, HRMS and thermogravimetric measurements. The thermal behaviour of the ligands showed that ligands 3.1-3.3 displayed similar decomposition patterns. Similar fragmentation patterns were observed for the iridium and cobalt complexes containing ligands 3.1 and 3.3. The complexes were tested in the oxidation of n-octane in two solvent systems, DCM and MeCN with H2O2 and t-BuOOH as the oxidants. The optimum substrate to oxidant ratio was found to be 1:5. No conversion was observed with H2O2. The conversion in DCM for the iridium catalysts was much higher than that of the cobalt catalyst. However, higher conversion was obtained in MeCN for the cobalt catalysts. No conversion was observed for the iridium catalyst in MeCN. The selectivity to ketones was much higher than to the alcohols, with only the C(1) position being most selective to the alcohols. The in situ, single pot testing of n-octane using a ruthenium precursor and ligand 3.1- 3.4 undertaken in DCM showed no conversion, whilst in MeCN a conversion of 17% was observed. The selectivity was similar to that obtained by the cobalt catalysts in MeCN. All testing showed that the catalyst containing ligand 3.1 was the most active giving the highest conversions in different solvent systems, which is attributed to the bite angle effect. / Thesis (M. Sc.)-University of KwaZulu-Natal, Durban, 2011.

M.Sc. / This dissertation deals with the syntheses of tridentate (O^N^N) coordination ligands [{2,4-di-tert-butyl-6-[(2-(3,5-RR-pyrazol-1-yl-ethylimino)-methyl] phenol}, R = H (L1), Me(L2), Ph(L3), t-Bu(L4)], which was reacted initially with MX2 (M = Fe, Co, Ni; X = Cl, Br). The ligands L1-L4 were also modified by functionalizing the phenol group in this ligand group to an ethoxy in L5 and L6 (L5 = [(3,5-di-tert-butyl-2-ethoxy-benzylidene)-[2-(3,5-dimethyl-pyrazol-1-yl)-ethyl]-amine, L6 = [(3,5-di-tert-butyl-2-ethoxy-benzylidene)-[2-(3,5-di-tert-butyl-pyrazol-1-yl)-ethyl]-amine)], or into a phenoxy in L7 (L7 = (3,5-di-tert-butyl-2-phenoxy-benzylidene-(2-pyrazol-1-yl-ethyl)-amine)). Another ligand L8 (L8 = [4-(4-tert-butyl-benzylidene)-[2-(3,5-dimethyl-pyrazol-1-yl)-ethyl]-amine], which was devoid of the phenoxy group was also synthesized. These modified ligands were also reacted with MX2 or PdCl(COD)Me to form bidentate (N^N) chelating complexes. Further modification of the ligand L1-L4, to replace the phenoxy pyrazolylimine unit with a source of oxygen donor other than a phenoxy led to the use of already known ligands L9, L10 (L9 = 2-(3,5-dimethyl-pyrazol-1-yl)-ethanol, L10 = 2-(3,5-di-tert-butyl-pyrazol-1yl)-ethanol and L11, where in L11, the alcohol moiety is replaced by an electron withdrawing chloro group, L11 = 1-(2-chloroethyl)-3,5-di-methyl-pyrazole). These ligands were also reacted with MX2 (M = Fe, Co, Ni, Pd; X = Cl, Br) to form complexes. The synthesized complexes were characterized by a combination of IR and NMR spectroscopy, mass spectrometry, microanalysis and in selected cases single crystal X-ray crystallography.

Phosphorus-Selenium chemistry has seen a surge in development over the last five to ten years thanks to the optimisation of the synthesis of 2,4-diphenyl-1,3,2,4-diselenadiphosphetane-2,4-diselenide, Woollins' Reagent. This selenium analogue of the well known Lawesson's Reagent has proved itself to be a valuable asset to modern inorganic chemistry, providing a route to novel heterocycles, as well as acting as a selenation reagent with a wide range of functional groups. A series of new ammonium phenylphosphonamidodiselenoate ligands were synthesised via the reaction of Woollins' Reagent with a range of amines. The products were obtained in high yields and could be used as ligands for the synthesis of novel metal complexes. The reaction of diisopropylamine N-isopropyl-P-phenylphosphonamidodiselenoate with nickel(II) acetate produces a dimeric structure, whilst the reaction with copper(II) acetate yields a beautiful cluster of the form Cu₆Se₃L₆. The phenylphosphonamidodiselenoate ligands were further reacted with a range of cis-Pt(PR₃)₂Cl₂ complexes to form a library of 20 novel compounds, which were studied by ³¹P{¹H}, ⁷⁷Se{¹H} and ¹⁹⁵Pt{¹H} NMR spectroscopy. The X-ray crystal structure of one of these compounds was obtained, which confirmed the atom connectivity and spatial arrangement of the complexes and the geometry around the platinum centre. During investigations into the above-mentioned platinum complexes, it was postulated that an increase in steric bulk of the phosphine ligands would aid crystallisation of the products. As such, trimesityl-, dimesitylphenyl- and mesityldiphenyl phosphine were synthesised and reacted with elemental sulfur and selenium and hydrogen peroxide, as well as Pt(cod)Cl₂ and K₂[PtCl₄], yielding nine new structures, all of which were characterised by X-ray crystallography, ³¹P{¹H}, ¹³C{¹H} and ¹H NMR spectroscopy. Finally Woollins' Reagent was reacted directly with a selection of metal complexes, yielding some new insights into its reactivity with inorganic moieties, which has been relatively sparsely reported until now.

Transition metal complexes derived from Schiff bases have rendered an important contribution to the development of modern coordination chemistry. Various stable compounds have been prepared having synthetic, biological, and physicochemical interest. In particular, complexes of salicylaldimines, B-ketoamines, and closely related ligand systems have been investigated.

Neste trabalho, propusemos um método autoconsistente de espaço direto para o calculo de estrutura eletrônica. O método se baseia no formalismo LNTO -ASA na representação fortemente ligada (light-binding) e no método de recorrência aliado ao terminador de Beer & Pettifor. Neste método o custo computacional cresce linearmente com o numero de átomos não equivalentes na cela primitiva sendo, portanto, ideal para tratar sistemas complexos que não apresentam periodicidade ou que possuem um grande numero de átomos não equivalentes por cela primitiva. Podemos, por exemplo, estudar de forma autoconsistente a estrutura eletrônica das vizinhanças de uma impureza com um custo computacional apenas cinco ou seis vezes maior que o de um metal puro. O método aqui proposto tem a vantagem adicional de ser fisicamente transparente. Para avaliarmos a eficácia do método, comparamos nossos resultados autoconsistentes obtidos para a liga cristalina ZR IND.2FE com os resultados obtidos pelo processo autoconsistente de espaço reciproco. O material em questão tem uma estrutura cristalina simples com seis átomos por cela primitiva e o calculo de estrutura eletrônica pode ser resolvido por métodos usuais de espaço reciproco. A presença do FE com sua banda d estreita e com uma alta densidade de estados no nível de Fermi tornara o processo de convergência não trivial. / In this work we have proposed a first-principles selfconsistent method which allows us to perform electronic structure calculations in real space. The scheme, based on the LNTO ASA formalism and the Recursion Method, enables us to evaluate the electronic structures of complex systems, with good degree of precision and low computational costs. Using Zr 2 Fe as test case, we compare our real-space results with those obtained in reciprocal space using the standard LMTO - ASA procedure. The agreement is very good showing the efficiency of the real-space approach. We note that the real-space method developed here presents advantages for the evaluation of local properties and can be applied for non-periodic systems. For instance, we can describe the electronic structure in a large region around a substitutional impurity with very little cost. lf we consider five shells around the impurity the cost in real-space will be about seven times the cost of the calculation for a mono atomic system.

Orientador: Massao Ionashiro / Banca: Grimaldo Marino / Banca: Roni Antônio Mendes / Resumo: Esse trabalho descreve a síntese, caracterização, estabilidade térmica e decomposição térmica dos mandelatos de metais de transição bivalentes, M(C6H5CH(OH)CO2)2 (M = Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II) no estado sólido, bem como o comportamento do ácido mandélico C6H5CH(OH)CO2H e seu sal de sódio. Os compostos foram estudados empregando termogravimetria e calorimetria exploratória diferencial (TG-DSC), espectroscopia de absorção na região do infravermelho (FTIR), TG-DSC acoplada FTIR, difratometria de raios X pelo método do pó, análise elementar e complexometria. Todos os compostos foram obtidos no estado anidro e a decomposição térmica ocorreu em duas ou quatro etapas consecutivas. O resíduo final até 320 °C (Mn), 345 °C (Fe), 400 °C (Co), 405 °C (Ni), 355 °C (Cu) e 575 °C (Zn) foi Mn2O3, Fe2O3, Co3O4, NiO, CuO e ZnO, respectivamente. Os resultados também forneceram informações sobre a coordenação do ligante, comportamento térmico e identificação dos produtos gasosos liberados durante a decomposição térmica destes compostos / Abstract: In this work, the synthesis, characterization, thermal stability and thermal decomposition of the bivalent transition metal mandelates in the solid state, M(C6H5CH(OH)CO2)2 (M = Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II), as well as the thermal behavior of mandelic acid C6H5CH(OH)CO2H and its sodium salt. The compounds were investigated employing simultaneous thermogravimetry and differential scanning calorimetry (TG-DSC), infrared spectroscopic (FTIR), TG-DSC coupled to FTIR, X-ray powder diffractometry, elemental analysis and complexometry. All the compounds were obtained in the anhydrous state and the thermal decomposition occurred in two or four consecutive steps. The final residue up to 320 °C (Mn), 345 °C (Fe), 400 °C (Co), 405 °C (Ni), 355 °C (Cu) and 575 °C (Zn) was Mn2O3, Fe2O3, Co3O4, NiO, CuO and ZnO, respectively. The results also provided information concerning the ligand's denticity, thermal behaviour and identification of the gaseous products evolved during the thermal decomposition of these compounds / Mestre