10.1021/cm010846h.s001
Claus G. Lugmair
Claus G.
Lugmair
Kyle L. Fujdala
Kyle L.
Fujdala
T. Don Tilley
T. Don
Tilley
New Tris(<i>tert</i>-butoxy)siloxy Complexes of Aluminum and
Their Transformation to Homogeneous Aluminosilicate
Materials via Low-Temperature Thermolytic Pathways
American Chemical Society
2002
surface area aluminosilicate xerogels
0.5 equiv
8 solution
heat flow
Acidity measurements
THF
HO
mullite formation
Compounds 2
Homogeneous Aluminosilicate Materials
1 H NMR spectroscopy
New Tris
DSC traces
PXRD
energy difference
DSC trace
27 Al MAS NMR spectra
2002-01-22 00:00:00
Journal contribution
https://acs.figshare.com/articles/journal_contribution/New_Tris_i_tert_i_-butoxy_siloxy_Complexes_of_Aluminum_and_Their_Transformation_to_Homogeneous_Aluminosilicate_Materials_via_Low-Temperature_Thermolytic_Pathways/3592734
The new tris(<i>tert</i>-butoxy)siloxy complexes of aluminum, Al[OSi(O<i><sup>t</sup></i><sup></sup>Bu)<sub>3</sub>]<sub>3</sub>(THF) (<b>1</b>), Al[OSi(O<i><sup>t</sup></i><sup></sup>Bu)<sub>3</sub>]<sub>3</sub>(HO<i><sup>i</sup></i><sup></sup>Pr)·0.5[Al(O<i><sup>i</sup></i><sup></sup>Pr)<sub>3</sub>]<sub>4</sub> (<b>2</b>), and [(<i><sup>i</sup></i><sup></sup>PrO)<sub>2</sub>AlOSi(O<i><sup>t</sup></i><sup></sup>Bu)<sub>3</sub>]<sub>2</sub> (<b>3</b>), were synthesized. Compounds <b>2</b> and <b>3</b> were structurally characterized by single-crystal X-ray crystallography.
Thermolysis of a toluene-<i>d</i><sub>8</sub> solution containing <b>1</b> and 0.5 equiv of [Al(O<i><sup>i</sup></i><sup></sup>Pr)<sub>3</sub>]<sub>4</sub> resulted in
the formation of <b>3</b> and free THF (by <sup>1</sup>H NMR spectroscopy). The low-temperature
decompositions of <b>1</b>, <b>2</b>, and <b>3</b> allowed for their use as single-source precursors to high surface
area aluminosilicate xerogels via solution (toluene) thermolyses. The DSC traces of the
xerogels derived from the 1:1 Al/Si precursors (<b>2</b> and <b>3</b>) exhibited sharp exothermic
transitions at ≈1000 °C, attributed to the crystallization of mullite, with that for the xerogel
from <b>3</b> having a larger associated heat flow. The DSC trace of the xerogel derived from <b>1</b>
exhibited a weak exothermic transition at a slightly higher temperature. Although these
xerogels have similar <sup>27</sup>Al MAS NMR spectra, their microstructures appear to be quite
different, as indicated by the substantially more efficient transformation to mullite (by PXRD)
of the xerogel from <b>2</b>. All of the xerogels are homogeneous; however, the microstructure of
the xerogel from <b>2</b> appears to more closely resemble that of mullite, given the enhanced
formation of mullite (by PXRD) and the reduced free energy difference associated with mullite
formation (by DSC). Acidity measurements characterized the Lewis/Brønsted site ratios as
1.2, 1.6, and 1.0 for the xerogels from <b>1</b>, <b>2</b>, and <b>3</b>, respectively.