Study of the reactions of immobilization of tungsten and molybdenum organometallic complexes on the polyhedral oligomeric silsesquioxanes for application in catalysis

Abstract

The present work is the synthesis and characterization of novel organometallic complexes of transition metal W(II) with different ligands in their coordination spheres, and the immobilization of these in solid matrices of polyhedral oligomeric silsesquioxane (POSS). The organometallic system proposed W(II) of the type [W(n3-allyl)(CO)2XL2], where L is a monodentate ligand and L2 is a bidentate ligand, are essentially exemplificative, and enable to develop the synthesis of the new species potentially active in catalysis. In this context, the effort is being made to obtain new complexes of W(II) by substitution of L or L2 by more ligands capable of increasing the catalytic activity of the complex, such as 3-amino-1,2,4-triazol-5-carboxylic acid (ATZAc) and/or 3-amino-1,2,4-triazole-5-thiol (ATT) and/or 4-amino-5-(4-pyridyl)-4H-1,2,4 -triazole-3-thiol (APTT). In this study, immobilization procedures will be tested with the aim of verifying the best methods for immobilization of the chemical species on the support surface POSS. According to the results the scope of the work to other types of complexes will extend with possible application in catalysis of olefin epoxidation. The first type of precursor material will be obtained from the reaction of octa-(3-chloropropyl) octasilsesquioxano (POSS-PrCl) with organic molecules, such as 3-amino-1,2,4-triazol-5-carboxylic acid (ATZAc) and/or 3-amino-1,2,4-triazole-5-thiol (ATT) and/or 4-amino-5-(4-pyridyl)-4H-1,2,4-triazol-3-thiol (APTT). This first type of material is called "POSS-Functionalized". The second type of material will involve the preparation of dendrimers through the organofunctionalization of the POSS with organic groups with amino terminus, similar to the dendrimers synthesized of amino cores. This second type of material will be called "POSS-Dendrimer." On the surfaces of these two types of precursors nanomaterials will be immobilized organometallic complex of tungsten ([W(n3-C3H5)(CO)2Br(NCME)2], where n3-allyl = C3H5 and NCME = acetonitrile), by chemical reaction , giving rise to the third type of material, which will be called "POSS-Catalyst." Aiming to make possible the chemical reaction of preparation of the "POSS-Catalyst" and therefore the determination of the maximum immobilization of organometallic complexes of W (II) on solid surfaces, several factors will be considered to optimize the results: a) Study of methods to viable the reaction of immobilization of organometallic complexes of W (II) on the surfaces of solid nanomaterials "POSS-functionalized" and "POSS-dendrimer"; b) study to determine the maximum amount of organometallic complexes that can be immobilized on the surfaces of solid supports organofunctionalized (surface saturation) using the isotherms of adsorption; c) Study of kinetic equilibrium; d) Study of thermodynamic parameters and activation energy. In these studies the mathematical equilibrium data, such as Langmuir, Freundlich, Temkin, Dubinin-Radushkevich (DR) models will be applied. The kinetic models such as pseudo-first-order, pseudo-second-order and others, will be used to describe the kinetic data. Thermodynamic experiments will be evaluated by the variation of the Gibbs energy, enthalpy and entropy of adsorption. The "POSS-Catalysts", resulting from the optimization study of the reactions of immobilization will be applied in catalytic tests of epoxidation reactions of olefins, such as geraniol, cis-3-hexene-1-ol, trans-3-hexene-1-ol, limonene, cyclooctene and styrene and / or other, and their catalytic activities can be compared with the one (s) (s) type (s) not supported (s). (AU)