Project PTDC/QUI/65507/2006
Energetics of metal Polyalkoxides
PI: J. P. Leal
(2009-2012)
Alkoxides are among the most useful compounds in synthesis and catalysis. The properties of metal alkoxides make them remarkable useful as molecular precursors and an important part of advanced materials for high-tech applications that relay on high purity metal oxides. They are also the precursors in many of the sol-gel methods developed in the last years. Alkaline and alkaline-earth metal ones are of extreme importance in industrial and pharmaceutical products (E.g. sodium or potassium phenoxides in the production of salicylic acid derivatives). However, in most cases; their energetics is not well known and in some cases not known at all. In our laboratories we had already studied reactions of alkaline and alkaline-earth metal and lanthanide metals with alcohols and phenols having in mind their energetic and applications as molecular precursors.
In this project it is proposed to determine the enthalpies of formation of alkaline ,alkaline-earth, lanthanide, aluminium and silicon polialkoxides Mx[O(CH2)nO]y (n = 2, 3, 4, 6, 8 ; x = 2y, M = Li, Na, K, Rb and Cs; x = y, M = Mg, Ca, Sr and Ba; x=2, y=3, M=Al, Ln; y=2x, M=Si). From these values, lattice energies and some other thermodynamic quantities could be calculated. They will be used in the enlargement and tuning of a previously developed model that allows the prediction of enthalpies of formation for experimentally unmeasured alkoxides and phenoxides (the model has already been tested in the alkalines, alkaline-earths and lanthanide alkoxides). The reactivity and the structure of each compound will be studied in order to see the possibility of practical applications as catalysts, synthetic precursors or starting materials for oxides deposition. Also the energetics of the formation of sols in sol-gel reactions will be addressed.
The synthesis of metal polialkoxides will be made by the dissolution of the metals in liquid ammonia, acid-base Lewis reactions or in alternative by the sol-gel route. The complexes will be characterized by metal, carbon and hydrogen elemental analysis, FTIR, NMR, FTICR/MS and X-ray diffraction (powder and single crystal). For application purposes their stability and oxidation route will be studied by TG and DSC.