N. Nava

Dimethyltin(IV) 2,6-disubstituted pyridine complexes

Abstract The synthesis and characterization of hypervalent pentacoordinated dimethyltin complexes obtained from the reaction of 2,6-disubstituted pyridine ligands with dichlorodimethyltin are reported. The complexes were characterized by mass spectrometry, 1H-, 13C- and 119Sn-NMR and Mossbauer spectroscopy, additionally the structures for two compounds were established by X-ray diffraction analysis. The structural parameters indicated pentacoordinated structures, which present Sn–N interaction and trigonal bipyramidal tin environment.

Structural studies of supported tin catalysts

Tin oxide was supported on aluminium oxide, titanium oxide, magnesium oxide and silicon oxide, and the resulting interactions between the components in the prepared samples and after reduction were characterized by Mössbauer spectroscopy. It was observed that in the oxide state, tin is present as SnO2 on alumina, magnesia and silica, but on titania tin occupies Ti sites in the structure. After hydrogen treatment at high temperatures, tin is reduced from Sn(4) to Sn(2) on alumina and titania; it is reduced from Sn(4) to Sn(0) on silica, and is practically not reduced on magnesia. These results reveal the degree of interaction between tin and the different supports studied.

Structural Behavior of Pt–Sn Supported on MgO

Pt–Sn supported on magnesia and alumina were characterized, before and after treatment with hydrogen, by Mössbauer spectroscopy and X-ray diffraction. For the calcined samples on both supports tin is present as SnO2 and platinum as metal. After reduction with hydrogen, platinum and tin diffuse into the magnesia lattice to form a solid solution. On alumina Sn(IV), Sn(II), Sn(0), Pt, Pt3Sn, PtSn and PtSn2 alloys are formed. The SnO interacts strongly with the alumina support. The catalytic activity of both Pt–Sn catalysts is strongly affected by the support. On alumina the dehydrogenation of cyclohexane is very high, whereas that on magnesia is almost non-active.

Mössbauer study of supported Pt—Sn

Pt—Sn supported on alumina was characterized before and after treatment with hydrogen by Mössbauer spectroscopy and X-ray diffraction. For the calcined sample tin is present as SnO2 and platinum as metal. After reduction with hydrogen, Sn(IV), Sn(II), Sn(0), Pt, Pt3Sn, PtSn alloys are formed. SnO interacts strongly with the support.

M?ssbauer spectroscopy of iron phosphate Fe3 (PO4)2(H2O)n pigments

In this work the Fe3 (PO4)2.(H2O)n pigment was synthesized from a FeSO4.7H2O and digested during some time in a solution of hydrogen ammonium phosphate at 75?C. This compound of a light blue colour was heated at 200?C, 300?C and 800?C, changing their colour and characterized by X-ray diffraction, scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and M?ssbauer spectroscopy. The M?ssbauer results of the compound subjected to thermal treatment show only the occurrence of Fe (III).

Mössbauer study of iron perovskites of Er, Sm and Nd

In solid state chemistry the perovskite structure is very important due to their interesting technological properties between this as ceramic pigments. In this work we present the synthesis of ErFeO3, SmFeO3 and NdFeO3. Its characterization by X-ray diffraction, SEM, energy dispersive X-ray analysis and Mossbauer spectroscopy was performed. energy dispersive X-ray analysis on the compounds was also conducted to confirm the assumptions made from X-ray diffraction results as well as Mossbauer spectroscopy showing the iron as Fe (III).