Cinetica e mecanismo da dissociação de complexos Fe(II)- - cetoiminas

AUTOR(ES)
DATA DE PUBLICAÇÃO

1980

RESUMO

In this work a investigation on kinetics and mechanisrn of the acid catalized of Iron (II)-a-diimine with unsymmetric ligands was carried out. The perchlorate complexes tris(pyridin-2-acetaldehyde,N-methylimine)Fe(II) (Fe(PMM)3(ClO4)2) and tris(pyridin-2-acetaldehyde, N-propylimine) Fe(II) (Fe (PMP)3 (CIO4)2) were studied. Kinetic runs were performed in acid concentration within 2 x 10 to 2,00 mol.dm in HCI + LiCl mixtures of ionic strenght 2,00 mol.dm, at 25,00, 30,00 and 35,00°C for Fe(PMM)3 and 35,00, 40,00 and 45°C for Fe(PMP)3. The reactions were followed photometric, by measuring the decrease with time in the maximum of absorbance at the charge transfer band of the complexes (558 nm for Fe (PMM)3 and 566 nm for Fe (PMP)3). The results were interpreted in terms of the general mechanism proposed by Basolo et al for the dissociation of metal chelates and extended by Vichi and Krumholz to chelates of unsymmetric ligands. The dissociation of Fe(PMP)3 could be described as occuring exclusively via initial rupture of one iron-nitrogen bond of the aliphatic moiety of one of the Iigands. In the case of Fe(PMM)3 the dissociation occur mostly via the initial rupture of the Fe--N(aliphatic) bond. The results were discussed on the basis of the steric effects operating in the half-bonded stationary intermediate which is predominant in iron-ketoimine complexes, compared with eletronic effects.

ASSUNTO(S)

dissociação

ACESSO AO ARTIGO

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