Síntese de complexos de metais com ditiocarbimatos e estudo de sua atividade como aceleradores na vulcanização da borracha natural

• Autor(a) principal: Cunha, Leandro Marcos Gomes
• Data de Publicação: 2008
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/2133
• topic: Complexos de zinco; Complexos de níquel; Ditiocarbimatos; Borracha natural; Aceleradores de vulcanização; Zinc complexes; Nickel complexes; Dithiocarbimates; Natural rubber; Accelerators of the vulcanization; CNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA::QUIMICA ORGANICA

This work describes the syntheses of eight metals complexes with dithiocarbimates, four of them of zinc and four of nickel. Dithiocarbimates are compounds structurally similar to dithiocarbamates, but less studied. The syntheses of the complexes were made in three stages: In the first one sulfonamides (RSO2NH2) were obtained through the reaction of adequate sulfonyl chlorides with a concentrated ammonia solution. In the second one potassium dithiocarbimates (RSO2N=CS2K2) were prepared through the reaction of sulfonamides with an equivalent of carbon disulfide and two equivalents of potassium hydroxide, in dimethylformamide. The third step consisted in the syntheses of the complexes through the reaction of two equivalents of potassium dithiocarbimates with an equivalent of an appropriate metal salt and two equivalents of tetraphenylphosphonium bromide in methanol:water 1:1. Thus, complexes with general formula [M(RSO2N=CS2)2]2-, (M=Zn, Ni), (R = methyl, ethyl, butyl, octyl) were obtained and isolated in the form of tetraphenylphosphonium salts, (Ph4P)2[M(RSO2N=CS2)2]. Data from Xray diffraction showed a tetrahedral geometry around the zinc(II) cation and a quadratic geometry around the nickel(II) cation. All the synthesized complexes were active as accelerators in the vulcanization of natural rubber, but they were slower than the commercial accelerators: CBS, TMTD and MBTS. Among the synthesized complexes, the zinc ones showed higher activity than the nickel ones. The size of the aliphatic chain of the ligand is an important factor in the activity of the compounds, whereas those with longer aliphatic chains were more active.