Gilson H. M. Dias
State University of Campinas
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Featured researches published by Gilson H. M. Dias.
Polyhedron | 2000
Cleber V. Ursini; Gilson H. M. Dias; Manfredo Hörner; Adailton J. Bortoluzzi; Milton K. Morigaki
Abstract 31P NMR spectroscopy measurements were used to establish the course for the stoichiometric-dependent reactions between [Au(PPh3)]+ and [Pt(CCPh)2(dppf)] (1), which for equimolar amounts afford as the unique product [Pt-{η3-C(CCPh)C(Ph)Au(PPh3)}(dppf)]+ (2), but any excess of 1 gives also [Pt(η2-PhCCCCPh)(dppf)] (3) [dppf=1,1′-bis(diphenylphosphine)ferrocene]. Both compounds 2 and 3 were obtained straightforwardly by the reactions of 3 with [Au(PPh3)]+ and [Pt(C2H4)(dppf)] with 1,4-diphenylbutadiyne, respectively. The X-ray crystal structure analysis of 3 confirmed a trigonal-planar coordination geometry about the platinum atom, and a bent η2-coordinated diyne ligand.
Journal of Non-crystalline Solids | 2000
Marcelo Hawrylak Herbst; Nelson M. Pinhal; Fábio A.T. Demétrio; Gilson H. M. Dias; Ney V. Vugman
Abstract Homoleptic amorphous platinum–fullerene compounds were synthesized from low-valent platinum precursors. Both variation of precursor and temperature of synthesis lead to different phases. Simultaneous observation of symmetric and antisymmetric fullerene vibrational modes in the platinum–fullerene IR and resonant Raman spectra support evidence for dimer and oligomer formations. Doublet splitting of fullerene ( I h point group symmetry) F 1u modes and observation of previously IR silent modes also indicate substantial local disorder at the fullerene moiety. X-band CW-EPR measurements, using the microwave power saturation technique, allows observation of at least two different relaxation behaviours, that are attributed to activation of efficient relaxation pathways in the compounds synthesized at 25°C. These processes are absent in fullerene[60] and much less effective in the platinum compound obtained at −45°C.
Polyhedron | 1992
Gilson H. M. Dias; Milton K. Morigaki
Abstract Iron-57 Mossbauer spectroscopy data are reported for [Fe(Bu t NC) 5 ], [Fe(CO) 4 (Bu t NC)] and [(PPh 3 ) 2 N][Fe(CO) 4 (CN)] complexes in order to examine the bonding character and geometrical changes of several iron penta-coordinate complexes. The small quadrupole splitting value of 0.88 mm s −1 measured for the distorted trigonal bipyramidal [Fe(Bu t NC) 5 ] differs significantly from these found for regular geometries. As a consequence of this unusual result, a new correlation method of analysis was proposed for 13 known structures of five-coodinate [FeL 5 ], axially substituted [Fe(CO) 4 L′] and [{Fe(CO) 4 } n L″] n− complexes (L = CO or Bu t NC), on the basis of deviations from the idealized trigonal bipyramidal structure and changes in the quadrupole splittings. Furthermore, correlations involving Mossbauer data and IR carbonyl stretching frequencies were used to answer more detailed electronic and stereochemical questions.
Química Nova | 2007
Zaine Teixeira; Suzan Pantaroto de Vasconcellos; Luzia Koike; Gilson H. M. Dias
In this work, we describe a new method for obtaining [Fe(CO)2[(h5-C5H5)Cl] employing simple techniques and low-cost reagents. It is worth mentioning that this method is faster than others reported in the literature. It was applied in laboratory classes for undergraduate students, exploring different concepts in organometallic chemistry and discussing the steps involved in the synthetic route.
Transition Metal Chemistry | 1994
Milton K. Morigaki; L. C. Machado; C. Larica; Gilson H. M. Dias
SummaryComplexes [Fe(t-BuNC)n(CO)5-n](n = 1 or 2) react with equimolar amounts of mercury(II) halides in acetone to form neutral iron-mercury adducts [Fe(t-BuNC) (CO)4−(HgX2)] and [Fe(t-BuNC)2(CO)3(HgX2)] (X = Cl or I), while [Fe(t-BuNC)5] reacts with solid mercury halides in petroleum ether to give the salts [Fe(t-BuNC)5(HgX)]-HgX3 (X = Br or I). Product assessment was based upon analytical and spectroscopic data, the Mössbauer effect and on molar conductivity studies.
Química Nova | 2014
Ramon K.S. Almeida; Cláudia Martelli; Gilson H. M. Dias; Julio Cesar Araujo da Silva
In this work, we present an efficient and inexpensive device for undergraduate chemistry classes aimed at teaching and learning the photolytic synthesis concepts. A photochemical reactor was tested for the synthesis of the organometallic compound enneacarbonyldiiron from iron pentacarbonyl in acetic acid, and its formation evidenced by FTIR analysis. Although similar devices have been described in other studies, none of these offered the simplicity, low cost, class-compatible reaction times and good yields afforded by the procedure reported herein.
Journal of Physics and Chemistry of Solids | 2003
Marcelo Hawrylak Herbst; Gilson H. M. Dias
Abstract Evidence of chemical reactivity of solid platinum-fullerene [Pt n C 60 ] compounds towards carbon monoxide is presented. The interaction was systematically studied by means of infrared spectroscopy, X-ray powder diffraction and thermogravimetric analysis. The interaction of carbon monoxide, even under low pressure, is confirmed by the appearance of infrared absorption bands in the CO stretching region at 2064, 2014 and 1991 cm −1 for the carbonylation products. The exceptions were those products with low Pt:C 60 ratios, which also displayed bands at 1870 and 1830 cm −1 . The data suggest that the CO coordination depends on the specific morphology of the solids, the original Pt:C 60 ratio, and the carbon monoxide nominal pressure. Therefore, these results indicate the formation of [(CO) x Pt] m species supported in a fullerene matrix mixed with [Pt n − m C 60 ] compounds. As there is a competition between carbon monoxide and fullerene molecules for the electronic density at the platinum centers, the nature of the CO interaction with [Pt n C 60 ] was found to be destructive, leading to the displacement of the latter. Nevertheless, the platinum-carbonyl species formed presents relatively high stability, as shown by desorption tests.
Transition Metal Chemistry | 1999
Milton K. Morigaki; L. C. Machado; Elias M. da Silva; C. Larica; Armando B. Filho; Gilson H. M. Dias
The reactions of [Fe(t-BuNC)3(CO)2] with HgX2 (X= Cl, Br or I) give two different types of iron-mercury halide complex, depending on the molar ratio of reactants used. An equimolar ratio of the reactants produces the neutral adducts [Fe(t- BuNC)3(CO)2(HgX2)],whereas two equivalents of HgX2 generate the electrolytes [Fe(t- BuNC)3(CO)2(HgX)]HgX3. The Mössbauer, i.r. data, and conductivity measurements of these complexes are presented and discussed in terms of their chemical structures and bonding.
Transition Metal Chemistry | 1992
Milton K. Morigaki; Gilson H. M. Dias
SummaryThe isocyanide-complex [Fe(t-BuNC)5] reacts with mercury(II) chloride in petroleum ether, to give the novel oxidative addition products [Fe(t-BuNC)5(HgCl)]+·[HgCl3]− (1) or [Fe(t-BuNC)5(HgCl)]2+[HgCl4]2− (2). Complex (2) is also obtained upon treating solutions of (1) with Na+[BH4]−, Na, or by addition of NaCl. Complex (1) reacts with [Fe(CO)5] to yield either (2) or [Fe(t-BuNC)5(HgCl)]+Cl− (3), depending upon the molar ratio of reactants. Complex (1) reacts with NH4+[PF6]−, in the presence oft-butyl isocyanide, to give [Fe(t-BuNC)5(HgCl)]+[PF6]− (4). These products have been characterized by elemental analysis, i.r. and n.m.r. spectra, and their ionic formulations established from conductance and molecular weight measurements on solutions.
Química Nova | 2004
Milton K. Morigaki; Elias M. da Silva; Carlos V. P. de Melo; C. Larica; Armando Biondo; Jair C. C. Freitas; Gilson H. M. Dias; Holgadinei Rodrigues Ribeiro
FeBr2 reacts with the S2C2(CN)22- ion (1:1 ratio) in the presence of an excess of t-BuNC in THF to give the mixed ligand [Fe(S2C2(CN)2)(t-BuNC) 4] compound. This neutral product with a formal oxidation state of two for the iron atom was characterized by conductivity measurements, and, i.r., Mossbauer, 13C and 1H n.m.r. spectroscopy. There is a Fe-C p back-donation strengthened towards isocyanide ligands, according to the data of 13C, 1H n.m.r. and Mossbauer spectroscopy.