Quimica e electroquimica molecular de complexos derivados da activacao de nitrilos, metilenoamidas e diazoalcanos

The synthesis and characterisation of the nitrile complexes cis- or trans-(ReC1(NCR)(dppe)_2) and (Re(NCR)_2(dppe)_2)"+ are described (ch. I and II). The cis isomers of the neutral complexes are susceptible to electrophilic attack at the #beta# position of the NCR ligand or at the metal (with formation of methyleneamido- or hydride-complexes), cis-to-trans isomerization induced by chemical oxidation, or substitution reactions of the non-phosphinic ligands (e.g., with formation of the related dinitrile or the monocarbonyl complexes). the cationic dinitrile compounds only undergo cis-trans isomerization or exchange of the counter-ion (Ch.II). The methyleneamido- or hydrido-complexes can be deprotonated (reversibly in the latter case) by reaction with a base to give the trans isomers of the neutral mononitrile species. The mechanism of the fats protonation of the (cis and trans) neutral compounds was established by stopped-flow techniques. The electrochemical studies of the abovementioned compounds (Ch. III) revealed an anodicallyinduced cis-to-trans isomerization of the (neutral and cationic) nitrile or monocarbonyl species as well as electroinduced deshydrogenation and deprotonation reactions of the metyleneamido - and hydrido-complexes. Some of these mechanisms were investigated by digital simulation of cyclic voltammetry. Moreover, ligand and metal site effects on the redox potential have been discussed, and the corresponding electrochemical parameters estimated. A preliminary study on the activation of diazo-compounds by Pt(0) metal centre with formation of symmetrical olefins is described in Chapter IV. Analyses of high-resolution N.M.R spectra were also performed in a number of casesAvailable from Fundacao para a Ciencia e a Tecnologia, Servico de Informacao e Documentacao, Av. D. Carlos I, 126, 1200 Lisboa / FCT - Fundação para o Ciência e a TecnologiaSIGLEPTPortuga