Sintese e reações de alguns compostos ciclicos de tres membros com complexos de metais de transição
AUTOR(ES)
Luiz Antonio Ortellado Gomez Zelada
DATA DE PUBLICAÇÃO
2004
RESUMO
With the aim of studying the reactivity of some cyclopropane derivatives with respect to certain transition metal complexes of the d group, the a-chlorine-a-(cyclopropiliden)-methyl acetates 1a and 1b, the alquinilcyclopropanes 2a-i and the 3-cyclopropil-2H-azirine 3a were synthesized. Reactions of these cyclopropanes with organometalic complexes of the nickel family, where the complexes were used both as reagents and catalysts, were studied. In these reactions, the metylenecyclopropanes 1a and 1b didn t show good reactivity with respect to the complexes investigated. An exception is Ni(cod)2 which formed rather insoluble and non-melting products, difficult to analyze. The low reactivity of this type of cyclopropanes was attributed to the presence of electron withdrawing groups linked to the C=C double bond, as weIl as to steric hindrance. It was shown that alquinylcyclopropanes react well with the (h-cyclopentadienyl)bis(etyIene)cobalt(I) 32, both in catalytic or in stoichiometric amounts, Ieading to the formation of intermediate complexes as well as of products of the catalytic cyclotrimerization and cyclocotrimerization, the later in the presence of benzonitrile. These products consisted of polysubstituted benzenic and piridinic compounds, as well as some stabIe complexes of (h-cyclopentadienyl)(h-tetrasubstituted cyclobutadierie )cobalt(I) type. It was verified, that the yield of the products decreased with increasing the size of the substituent groups at the acetylenes 2a-i, which supports that steric hindrance difficults the approach of those ligands to the metal of the catalyst. The reaction of 3-cyclopropyl-2H-azirine 3a with paIadiumbis(benzonitrile) dichloride 23 leads to the formation of the corresponding complex 57a. The opening of the complexed azirine, studied under different conditions, lead to the formation of different complexes and of the pirazine 63a. This pirazine has one of its cyclopropane rings opened only when refluxed with trifluoromethanesulfonic acid in toluene. CycIopropane ring opening was not observed in the other reactions investigated. When reacted with acetylenedimetyldicarboxylate in the presence of hexahydrated cobalt dicloride, azirine 3a formed the cyclocotrimer 68a and the pirazine 63a as well as polymeric products. In the presence of moIybdenium and nickel complexes, cyclocodimerization and formation of polysubstituted pyrrols was observed.
ASSUNTO(S)
ACESSO AO ARTIGO
http://libdigi.unicamp.br/document/?code=vtls000332432Documentos Relacionados
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