Browsing by Author "Munoz Castro, Alvaro"

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    New bis(azolylcarbonyl)pyridine chromium(III) complexes as initiators for ethylene polymerization
    (ELSEVIER SCIENCE SA, 2011) Hurtado, John; Ugarte, Javiera; Rojas, Rene; Valderrama, Mauricio; Mac Leod Carey, Desmond; Munoz Castro, Alvaro; Arratia Perez, Ramiro; Froehlich, Roland
    Reaction of 2,6-pyridinedicarbonyl dichloride with 3,5-dimethylpyrazole and 1H-indazole, respectively, yield the tridentate ligands 2,6-bis(3,5-dimethylpyrazol-1-ylcarbonyl)pyridine (1) and 2,6-bis(indazol-1-ylcarbonyl)pyridine (2). The molecular structure of the new compound (2) was determined by single-crystal X-ray diffraction. These ligands react with CrCl3(THF)(3) in THF to form neutral complexes of general formula [CrCl3{2,6-bis(azolylcarbonyl)pyridine-N,N,N}] (3, 4) which were isolated in high yield as air stable green solids and characterized by elemental analysis, magnetic moment, IR, and mass spectroscopies. Theoretical calculations predict that the thermodynamically preferred structure of the complexes is the fac configuration. After reaction with methylaluminoxane (MAO) the chromium(III) complexes are active for the polymerization of ethylene. (C) 2011 Elsevier B.V. All rights reserved.
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    pi-donor/acceptor effect on lindqvist type polyoxomolibdates because of various multiple-bonded nitrogenous ligands
    (AMER CHEMICAL SOC, 2007) Mac Leod Carey, Desmond; Munoz Castro, Alvaro; Bustos, Carlos J.; Manriquez, Juan M.; Arratia Perez, Ramiro
    The electronic structures of Lindqvist type functionalized polyoxometalates (POM) ([Mo6O18R](n-) R = O, NO, NAr, NNAr, NNAr2; n = 2, 3) have been investigated using density functional methods. We discuss the role of the replacement of terminal oxo ligands by pi-donor/acceptor multiple-bonded nitrogenous ligands on the basis of geometrical parameters, charge analyses, reactivity indexes, and vibrational spectra. The calculated reactivity indexes (chemical potential, electronegativity, hardness, and electrophilicity) indicate that the most reactive functionalized POMs are those substituted by pi-acceptor ligands. These pi-acceptor ligands induce a decrease in the hardness and an increase in the chemical potential and electrophilicity, thus increasing the reactivity. Our calculations are in reasonable agreement with reported experimental data.
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    Toward the Synthetic Control of the HOMO-LUMO Gap in Binuclear Systems: Insights from Density Functional Calculations
    (AMER CHEMICAL SOC, 2010) Munoz Castro, Alvaro; Mac Leod Carey, Desmond; Morales Verdejo, Cesar; Chavez, Ivonne; Manuel Mariquez, Juan; Arratia Perez, Ramiro
    Computational methods based on density functional theory have been applied to address the design of tailored HOMO-LUMO gap bimetallic complexes. We focus our attention on the [Cp*Fe-(L)-FeCp*] system, where two ferrocenyl units are linked through the dianion of fused ring ligands such as pentalene, s-indacene, dicyclopenta-[b,g]-naphthalene, dicyclopenta-[b,l]-anthracene and dicyclopenta-[b,l]-tetracene Our DFT calculations on the title organometallic complexes suggest a controlled decrease in the HOMO-LUMO gap, which is desirable for studies on electron-transfer phenomena, as well as the design potential devices for molecular electronic purposes.