Estudo da interação entre SnCl4 e ligantes O e N-doadores por espectroscopia vibracional

AUTOR(ES)
DATA DE PUBLICAÇÃO

1980

RESUMO

In this work the interaction of tin (IV) tetrachloride with monodentated ligands of Gutmann s scale was studied, by analysing the vibrational spectra of 23 complexes with the general formula SnL2Cl4. It was observed that this scale can be used as a measurement of interaction strengths since the wavenumber of the stretching v(Sn-Cl) decrease as the interaction strength in crease. However, vibrational spectroscopy can not be used to compare interaction of ligands with different donor atoms. Within a serie of compounds with the same donor atom the comparison is viable. Vibrational spectroscopy proved to be a very useful technique in the determination of the geometry of the complexes studied. In particular, the extensive use of Raman spectroscopy permited the stablishment of another criterion to assign the configurations. The two above observations revealed that the isomerism depends on the interaction strength. To isolate a trans isomer, it was necessary, but not sufficient, that the ligand be of medium to strong strength. This conclusion was found to be valid for the cis-trans transformation in the solid state for some complexes. The non-ligand interaction model proved to be useful to understand these observations, but it was necessary to introduce additional interactions. The measurement of the enthalpies for the cis-trans transformation in the solid also showed that entropic terms are important in determining what isomer is isolated from solution. The use of the Gutmann s scale together with results of thermochemical rneasurements of the interaction of SnCl4 with ligands other than O- and N- donor, and the analysis of the results of vibrational and Mössbauer spectroscopies showed that the interaction of S-, Se-, P- and As- donor is probably made preferencially via the 5s tin orbital. However this does not mean that the trans isomer is more stable than the cis one, nor that the complexes with those ligands are more stable than those with O- and N-donors, where this preference is not revealed.

ASSUNTO(S)

estanho - compostos isomerismo espectroscopia de raman

ACESSO AO ARTIGO

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