Resumo: Neste trabalho novos complexos nitrosilos de rutênio (II) contendo bifosfinas foram obtidos e caracterizados. A série de complexos [RuCl3(NO)(P-P)] (1) foi utilizada como precursora na obtenção de compostos do tipo [Ru(pyS)2(P-P)] (2), P-P = dppe, c-dppen, dppp e dppb e [Ru(pyS)2(NO)(η1-P-PO)]PF6 (3), P-P = dppm e dppb; pyS = 2-mercaptopiridina, em rendimentos e pureza satisfatórios. Utilizou-se as técnicas usuais para caracterização dos complexos, entre elas: espectroscopias IV, UV/vis e RMN multinuclear (1H, 13C{1H} e 31P{1H}), voltametria cíclica, voltametria de pulso diferencial e análise elementar. A maioria dos compostos forneceu monocristais adequados para estudos por difração de raios-X. Os complexos do tipo (1) foram obtidos por rotas sintéticas já estabelecidas em nossos laboratórios. O inédito fac-[RuCl3(NO)(c-dppen)] foi isolado e caracterizado, tendo inclusive a estrutura cristalográfica resolvida. Este fato permitiu a realização de interessantes comparações deste com o isômero mer-[RuCl3(NO)(dppb)]. Adicionalmente, obtevese a estrutura cristalográfica do [RuCl3(NO)(c-dppen)] e realizou-se pela primeira vez ensaios eletroquímicos para toda a série (1) e experimentos de RMN multinuclear para o mer-[RuCl3(NO)(dppb)]. Assim, aproveita-se a oportunidade para algumas discussões adicionais, importantes para o melhor entendimento da série como um todo e para fins de comparação com os complexos derivados. Os produtos isolados nas reações com a pySH mostraram ser dependentes da bifosfina utilizada, já que o mesmo procedimento foi utilizado para obtenção dos derivados (2) e (3). A série (2) acima citada, com exceção do derivado com a c-dppen que é inédito, foi obtida anteriormente na literatura por rota de síntese diferente da aqui descrita. Apresentase a caracterização e discussão dos resultados ...(Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In this work new nitrosyl complexes of ruthenium (II) containing diphosphines were obtained and characterized. The series of compounds [RuCl3(NO)(P-P)] (1) was used as the precursor to obtain compounds of the type [Ru(pyS)2(P-P)] (2), P-P = dppe, c-dppen, dppp and dppb and [Ru(pyS)2(NO)(η1-PPO)] PF6 (3), P-P = dppm and dppb; pyS = 2-mercaptopyridine, in acceptable yields and purity. Standard techniques were used for characterization of the compounds, among them: infrared, visible-UV and multinuclear NMR (1H, 13C{1H} and 31P{1H}) spectroscopies, cyclic voltammetry, pulse diferential voltammetry and elemental analysis. Most of the studied complexes supplied crystals suitable for X-ray crystal structure analysis. Compounds of type (1) were obtained by synthetic routes previously established in our laboratories. The unpublished fac-[RuCl3(NO)(dppb)] was isolated, characterized and had its crystallographic structure solved. This fact allowed interesting comparisons with the geometrical isomer mer-[RuCl3(NO)(dppb)]. In addition, the crystallographic structure of the [RuCl3(NO)(c-dppen)] was obtained and electrochemical characterization for all series (1) as well as multinuclear NMR experiments for the mer-[RuCl3(NO)(dppb)] were carried out for the first time. These studies offer us the opportunity for some additional discussions about the precursor complexes important to the comparisons with the results for the derivative compounds. The isolated products of the reactions with 2-mercaptopyridine ligand showed to be dependent on the diphosphine from the precursor, since the same procedure was used for obtaining derivatives (2) and (3). The series (2), mentioned above, was described previously in the literature, except for the c-dppen derivative, utilizing another synthetic route. The characterization and discussion ...(Complete abstract, click electronic access below) / Orientador: Alzir Azevedo Batista / Coorientador: Luiz Antônio A. de Oliveira / Mestre

Made available in DSpace on 2014-06-11T19:29:10Z (GMT). No. of bitstreams: 0 Previous issue date: 2001Bitstream added on 2014-06-13T20:59:20Z : No. of bitstreams: 1 poelhsitz_g_me_araiq.pdf: 1569742 bytes, checksum: 1c42137408ccfde6142b90c3644361e4 (MD5) / Neste trabalho novos complexos nitrosilos de rutênio (II) contendo bifosfinas foram obtidos e caracterizados. A série de complexos [RuCl3(NO)(P-P)] (1) foi utilizada como precursora na obtenção de compostos do tipo [Ru(pyS)2(P-P)] (2), P-P = dppe, c-dppen, dppp e dppb e [Ru(pyS)2(NO)(η1-P-PO)]PF6 (3), P-P = dppm e dppb; pyS = 2-mercaptopiridina, em rendimentos e pureza satisfatórios. Utilizou-se as técnicas usuais para caracterização dos complexos, entre elas: espectroscopias IV, UV/vis e RMN multinuclear (1H, 13C{1H} e 31P{1H}), voltametria cíclica, voltametria de pulso diferencial e análise elementar. A maioria dos compostos forneceu monocristais adequados para estudos por difração de raios-X. Os complexos do tipo (1) foram obtidos por rotas sintéticas já estabelecidas em nossos laboratórios. O inédito fac-[RuCl3(NO)(c-dppen)] foi isolado e caracterizado, tendo inclusive a estrutura cristalográfica resolvida. Este fato permitiu a realização de interessantes comparações deste com o isômero mer-[RuCl3(NO)(dppb)]. Adicionalmente, obtevese a estrutura cristalográfica do [RuCl3(NO)(c-dppen)] e realizou-se pela primeira vez ensaios eletroquímicos para toda a série (1) e experimentos de RMN multinuclear para o mer-[RuCl3(NO)(dppb)]. Assim, aproveita-se a oportunidade para algumas discussões adicionais, importantes para o melhor entendimento da série como um todo e para fins de comparação com os complexos derivados. Os produtos isolados nas reações com a pySH mostraram ser dependentes da bifosfina utilizada, já que o mesmo procedimento foi utilizado para obtenção dos derivados (2) e (3). A série (2) acima citada, com exceção do derivado com a c-dppen que é inédito, foi obtida anteriormente na literatura por rota de síntese diferente da aqui descrita. Apresentase a caracterização e discussão dos resultados... / In this work new nitrosyl complexes of ruthenium (II) containing diphosphines were obtained and characterized. The series of compounds [RuCl3(NO)(P-P)] (1) was used as the precursor to obtain compounds of the type [Ru(pyS)2(P-P)] (2), P-P = dppe, c-dppen, dppp and dppb and [Ru(pyS)2(NO)(η1-PPO)] PF6 (3), P-P = dppm and dppb; pyS = 2-mercaptopyridine, in acceptable yields and purity. Standard techniques were used for characterization of the compounds, among them: infrared, visible-UV and multinuclear NMR (1H, 13C{1H} and 31P{1H}) spectroscopies, cyclic voltammetry, pulse diferential voltammetry and elemental analysis. Most of the studied complexes supplied crystals suitable for X-ray crystal structure analysis. Compounds of type (1) were obtained by synthetic routes previously established in our laboratories. The unpublished fac-[RuCl3(NO)(dppb)] was isolated, characterized and had its crystallographic structure solved. This fact allowed interesting comparisons with the geometrical isomer mer-[RuCl3(NO)(dppb)]. In addition, the crystallographic structure of the [RuCl3(NO)(c-dppen)] was obtained and electrochemical characterization for all series (1) as well as multinuclear NMR experiments for the mer-[RuCl3(NO)(dppb)] were carried out for the first time. These studies offer us the opportunity for some additional discussions about the precursor complexes important to the comparisons with the results for the derivative compounds. The isolated products of the reactions with 2-mercaptopyridine ligand showed to be dependent on the diphosphine from the precursor, since the same procedure was used for obtaining derivatives (2) and (3). The series (2), mentioned above, was described previously in the literature, except for the c-dppen derivative, utilizing another synthetic route. The characterization and discussion ...(Complete abstract, click electronic access below)

Thesis (Ph.D.) - James Cook University, 2005. / Journal publications by the author contained on CD-ROM. Typescript (photocopy) Includes bibliographical references.

This thesis work is based on an investigation of intermediates involved in various metal mediated catalytic reactions such as hydrogenation, hydroboration, functionalization of methane etc. An intermediate dictates the energetics of the catalytic cycle of these reactions. Therefore, it is important to study such types of intermediates in order to design a better catalyst. These intermediates are called σ-complexes in which a σ-bond is coordinated to the metal center at some stage of the reaction coordinate. These species are rarely stable at ambient conditions which create difficulties in exploring their chemistry. Our aim is to study the effect of ancillary ligands on the coordination properties of a σ-bond ligand. We chose two different classes of σ-complexes – one contains a B–H σ-bond as a ligand, i.e., σ-borane complex and another contains a H–H σ-bond as a ligand, i.e., σ-dihydrogen complex. Both M–H–B and M–H2 interactions are 3-center-2-electron coordination bonds comprised of two bonding components. One is σ-donation, which is present in both and another is π-back donation from the metal center, which is negligible in the σ-borane complexes contrary to the σ-dihydrogen complexes. The bonding characteristics of M–H–B and M–H2 interactions suggest that an electron deficient metal center is necessary to study the σ-borane complexes with reasonable stability. Thus, we selected an early transition metal, i.e., Cr(0) bearing arene and CO ancillary ligands, for studying the σ-borane complexes. On the other hand, the cis-dihydrogen/hydride and cis-dihydrogen chloride complexes were studied on a late transition metal center, i.e., Ru(II) bearing phosphine and N–N bidentate ligands. Ammonia-borane is known to be a potential hydrogen storage material. Therefore, we picked up the catalytic dehydrogenation reaction of this compound and intended to investigate the interaction between a metal center and the BH σ-bonds of amine-boranes. We characterized the σ-borane complexes [(η6-arene)Cr(CO)2(η1-H–BH2•NMe3)] (arene = fluorobenzene, benzene, and mesitylene), and observed an interesting correlation between the electronics and stability of these species. This was the first report of σ-borane systems possessing an η6-arene ligand. A prototype homobimetallic σ-borane complex, [(η6-C6H5CH2NMe2•BH2–HCr(CO)5)Cr(CO)3] was characterized using single crystal X-ray crystallography. An intramolecular σ-borane complex, (η1-(η6-C6H5CH2NMe2•BH2–H))Cr(CO)2 was found to possess an interesting chelation of the η6-arene, and BH coordination sites of its amine-borane moiety with the Cr(0) center. These σ-borane complexes showed an interesting dynamics in the binding interface between the metal center and the borane ligand. Free energy of activation (ΔG#) for this process was estimated to be 30-40 kJ/mol. To explore certain σ-dihydrogen complexes we investigated the chemistry of cis-dihydrogen/hydride complexes of Ru(II) bearing phosphine and N-N bidentate ligands cis,trans-[RuH(η2-H2)(PPh3)2(N-N)][OTf] (N-N = 2, 2′-bipyridyl, 2, 2′-bipyrimidine) in detail. In those cases, we established that the adjacent hydride ligand has large influence on the dihydrogen coordination. The η2-H2 and hydride ligands showed a single 1H NMR spectral signal due to fast site exchange among each other. We established the mechanism and calculated the free energy of activation (ΔG# = 8-13 kJ/mol) of this dynamics. These complexes were found to be stable at ambient conditions although, a labile dihydrogen ligand is present in the coordination sphere of the metal center. In fact, we could obtain the single crystals of cis,trans-[RuH(η2-H2)(PPh3)2(bpy)][OTf]. The molecular structure of a σ-complex in which a σ-bond (before it gets completely formed or broken) acts as a ligand is what fascinates this area in chemistry. A cis-dihydrogen chloride complex, cis,trans-[RuCl(η2-H2)(PPh3)2(bpm)][OTf] was characterized unambiguously using NMR spectroscopy. The H-H distance (dHH) for the η2-H2 ligand of these complexes were estimated to be 0.9-1.0 Å. We attempted to observe some σ-methane species spectroscopically at low temperatures. Unfortunately, these species were quite unstable for exhibiting the NMR spectral signals even at low temperatures. Nevertheless, we investigated the reactivity of cis,trans-[RuHX(PPh3)2(N-N)] (X = H, Cl; N-N = 2, 2′-bipyridyl, 2, 2′-bipyrimidine) towards a methylating agent, CH3OTf. This reaction resulted in methane evolution by the combination of the hydride ligand of a Ru(II) complex and the CH3+ moiety of CH3OTf. This reaction was carried out in a sealed tube inside a NMR probe at ~183 K and monitored for a long period of time; however, the methane bound metal species was not observed. Perhaps, the longevity of this class of σ-methane complex falls below the NMR time scale.