Síntese e caracterização de compostos diorganoestânicos com ácido dl-mandélico

Abstract

Por reação de quantidades eqüimoleculares de R2SnO ou R2SnCl2 (R = -CH3; -C4H9) com ácido dl-mandélico, C6H5CH(OH)COOH, em meio de etanol, foram obtidos novos compostos formulados como [(LR2Sn)2O] [L= C6H5CH(OH)COO-], nos quais o átomo de estanho é pentacoordenado, com o ligante L estabelecendo uma ligação bidentada através dos átomos de oxigênio dos grupos ácido e hidroxila alcoólica. Nas mesmas condições, nenhum produto obtido a partir da reação de (C6H5)2SnO ou (C6H5)2SnCl2 pode ser identificado. No entanto, quando da reação de (C6H5)2SnCl2 com ácido dl-mandélico, em meio de acetonitrila, foi preparado um composto dimérico hexacoordenado formulado como [L(C6H5)2SnCl]2. Este composto não pode ser isolado de forma pura e está misturado com 7% de impurezas não identificadas, cujos parâmetros de interação hiperfina sugerem tratar de estanho tetravalente octaedricamente coordenado por oxigênio. Os compostos obtidos foram caracterizados por determinação de ponto de fusão, microanálise e espectroscopias i.v. e Mössbauer.

Synthesis and Characterization of Dibutyltin Compounds with α-Amino Acids

“…The evaluation of the infrared spectra of glycine, DL-valine, L-leucine and DL-phenylalanine allowed to assign the νCOOass values which were in good agreement with the literature data [20]. In the infrared spectra of I to IV relatively small shifts for the νCOOass values were verified for the highest region in the spectra of the complexes, in relation to the free α-amino acids.…”

“…In the experiments for the synthesis of the dibutyltin compounds described in this work, it was verified that the relative reactivity of the α-amino acids ligands was sensibly lower than the one of α-hydroxycarboxylic acids used in the synthesis of the organotin compounds also previously described by the authors [17][18][19][20].…”

“…Due to its insolubility for compounds II and IV it was not possible to record the NMR spectra. The insolubility of II and IV may be attributed to certain polymerization degree, as observed for diorganotin compounds with α-hydroxycarboxylic acid [17,20].…”

“…The [15,16]. In the first case, in the infrared spectra of both complexes the νCOOass values were shifted to 1605 cm -1 for free amino acids and to 1629 cm -1 for the derivatives [1,11,[20][21][22][23][24], whereas in the second case, in the infrared spectra of both complexes the νCOOass values were shifted to 1600 and 1595 cm -1 for free amino acids and to 1610…”

“…The initial and final temperatures of thermal decomposition process and the thermogravimetric data for the dibutyltin complexes are shown in For the DL-phenylalaninate derivative (IV), a hexacoordinated specie, the thermal degradation starts at 165 o C. Table 5. respectively) it can be concluded that the compound I and III can exist as monomeric species in solid-state while for the compounds II e IV, may be a sign of a certain polymerization degree [15][16][17]20]. This observation is reinforced by minor solubility of the compounds II and IV in relation to the solubility of the compounds I and III, described to get their respective 119m Sn-NMR spectra.…”