TGA of the product of the reaction of  Mg[Al(OPri)4]2 with catechol

Metal Alkoxide Chemistry


 Volatile, liquid mixed metal alkoxides, MM'(OR)n can be obtained for various combinations of metals and these species are potential CVD sources for mixed metal oxide ceramics. In fact, we have utilized Mg[Al(OPri)4]2 to form dense spinel, MgAl2O4, films.  However, volatile compounds of the alkali metals are rare and in this project we will turn our attention toward precursors of mixed metal oxides which contain an alkali metal.  We have discovered a liquid, polymeric alcoholate {(PriOH)2K[Al(OPri)4]n, which volatilizes when heated in HOPri vapor. We believe that the polymeric chain [K(-OPRi)2Al(-OPRi)2]n is broken and potassium becomes further solvated (PriOH)nK[Al(OPri)4], which is volatile because the metal atoms are encased in a sheath of non-polar groups. To improve stability we wish to a cage an alkali metal in a ligand, which is attached to the second metal. We have developed syntheses for HO(CH2)n(benzyl-18-crown-6). We will employ these alcohols to form alkali metal/aluminum-alkoxides:

HO(CH2)n(benzyl-18-crown-6) + M (or MR) MO(CH2)n(benzyl-18-crown-6)

 MO(CH2)n(benzyl-18-crown-6) +  Al(OR)3  M(benzyl-18-crown-6)(CH2)nOAl(OR)3 

using the procedures we have developed for M[Al(OR)4]n complexes. We anticipate the alkali metal will be encapsulated in the crown ether yielding monomer complexes. Characterization will be by the standard spectroscopic (heavily NMR) techniques and, when appropriate, by X-ray.  Upon completion of the syntheses, compounds will be tested as CVD precursors.

We have determined the crystal structure of Mg[Al(OPri)4]2.2DMF. This is very similar to the previously characterized iso-propanol adduct, but appears to be less prone to solvate dissociation.  

 Catechol and 3,4-dihydroxybenzaldehyde react with Mg[Al(OPri)4]2 liberating HOPri and forming mixed alkoxy/aryloxy derivatives. These species appear to thermally degrade to oxo/aryloxy species. A TGA of the decomposition of the catechol derivative is shown above. The first stage corresponds to the loss of thf solvate and the second involves largely the decomposition of isopropyl groups

Last Modified: 03/19/2013

Chemistry Department
James Madison University
Harrisonburg, VA 22807