- ACS MEETING - DALLAS, TEXAS
- MARCH 29 - APRIL 2, 1998
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- Barron Research
Group
- Posters and
Talks
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- CHALCOGENIDE EXCHANGE REACTIONS OF
[(tBu)Ga(Te)]4. Bradley D. Fahlman and Andrew
R. Barron* Department of Chemistry, Rice
University, Houston, Texas 77005
The reaction of [(tBu)Ga(Te)]4 with elemental
sulfur or selenium yields the corresponding cubane compounds,
[(tBu)Ga(E)]4 (E = S, Se), via sequential chalcogenide exchange
reactions. Each of the mixed cubane intermediate compounds,
[(tBu)4Ga4(Te)4-x(E)x] (x = 1, 2, 3, 4) have been characterized by
NMR spectroscopy and mass spectrometry. The kinetics of the
chalcogenide exchange reactions have been investigated under pseudo
first order conditions. The observed reactions are rationalized by a
consideration of the relative reduction potentials of the chalcogens.
In addition, the analogous reaction with iodine will be reported as
well as metal exchange reactions.
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- MOCVD OF GALLIUM SULFIDE USING GALLIUM
DIALKYL-DITHIOCARBAMATES AS SINGLE SOURCE
PRECURSORS. Andrea Keys,a Simon G. Bott,b
and Andrew R. Barron,a* (a) Department
of Chemistry, Rice University, Houston, Texas 77005, (b)
Department of Chemistry, University of Houston, Houston, Texas
77204.
The MOCVD growth of gallium sulfide (GaS) thin
films will be reported using the dialkyl-dithiocarbamate precursors,
(tBu)2Ga(S2CNR2) (R = Me, Et, nPr, iPr). The new precursor molecules
have been characterized by NMR and IR spectroscopy and mass
spectrometry, while their volatilities, including DH and DS of
sublimation, have been determined by thermogravimetric analysis.
Characterization of the thin films is accomplished by XRD and
micro-probe analysis.
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- CARBOXYLATE ALUMOXANES: ENVIRONMENTALLY
BENIGN PRECURSORS FOR DEVELOPING ALUMINUM BASED CERAMIC MEMBRANES
AND FILTERS. Christopher D. Jones,a Mark
R. Wiesner,b and Andrew R. Barron,a,c* (a) Department of Chemistry,
Rice University, Houston, Texas 77005,
(b) Department of Environmental Science and Engineering, Rice
University, Houston, TX 77005, (c) Department of Mechanical
Engineering and Materials Science, Rice University, Houston, Texas
77005.
The objective of our research is the development
of nano, meso, and macro scale aluminum based ceramic membranes and
filters from carboxylate alumoxanes. Carboxylate alumoxanes are
organic substituted alumina nano-particles synthesized from boehmite
in aqueous solution which are an inexpensive and
environmentally-benign precursor for the design and fabrication of
these membranes. The size of the carboxylate ligand on the alumoxane
controls the porosity during sintering to alumina. By varying the
size of the ligand, membranes of different porosity can then be
fabricated. The membranes will be characterized by atomic force,
scanning electron, and transmission electron microscopy, X-ray
diffraction, and flow measurements.
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- INORGANIC-ORGANIC EPOXY
COMPOSITE MATERIALS USING CARBOXYLATE-ALUMOXANES. Cullen T. Vogelson,a Simon G. Bott,b and Andrew R. Barron,a,c*
(a) Department of
Chemistry, Rice University, Houston, Texas 77005, Department of
Chemistry, University of Houston, Houston, Texas 77024, (c)
Department of Mechanical Engineering and Materials Science, Rice
University, Houston, Texas 77005.
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- We report that p-hydroxybenzoate
or lysine substituted alumoxanes are readily prepared from the
reaction of boehmite, [AlO(OH)]n, with the parent acid. The
surface hydroxides and amines of these alumoxanes reacts with
epoxides such as diglycidylether bisphenol-A (DGEBPA) to give a
new class of inorganic-organic hybrid material. Details of the
process will be reported as well as NMR and X-ray structural
studies of model systems. Physical properties of a variety of
functionalized alumoxane based composites will be discussed, and
their applications in structural materials will be presented.
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- INTRA-MOLECULAR COMPLEXATION
IN STERICALLY CROWDED ARYLOXIDES OF ALUMINUM. Julie A. Francis,a Simon G. Bott,b and Andrew R. Barron, a*
(a) Department of
Chemistry, Rice University, Houston, Texas 77005 (b) Department of
Chemistry, University of Houston, Houston, Texas 77204.
(1)
Sterically crowded aryloxide
compounds of aluminum have been prepared with intra-molecular Lewis
acid-base interactions (1) as model compounds for the latent Lewis
acidity of alkyl-alumoxanes. A variety of Lewis base groups (ERx) are
compared and their structures and reactivity are compared.
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- INTRA-GRANULAR CERAMIC
POROSITY USING CARBOXYLATE-ALUMOXANES. Rhonda L.
Callender,a Mark R.
Wiesner,b and Andrew R. Barrona,c* (a) Department of Chemistry, Rice University,
Houston, Texas 77005, (b) Department of Environmental Science and
Engineering, (c) Department of Mechanical Engineering and
Materials Science, Rice University, Houston, Texas 77005.
Carboxylate-alumoxanes,
[Al(O)x(OH)y(O2CR)z], have been used as precursors to a-alumina
bodies. The type of porosity in the resultant ceramic body is shown
to be dependent on the identity of the carboxylate substituent (R).
While the use of methoxyethoxyethoxyacetic acid [MEEA-H,
HO2CCH2(OCH2CH2)2OCH3], methoxyethoxyacetic acid [MEA-H,
HO2CCH2OCH2CH2OCH3], and methoxyacetic acid [MA-H, HO2CCH2OCH3]
substituted alumoxanes results in the formation of inter-granular
porosity, the acetic acid [A-H, HO2CCH2] allows for the formation of
intra-granular pores. The formation of intra-granular porosity is
discussed with respect to a self-seeding spontaneous nucleation
process.
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- ALUMINUM
CHEMISTRY OF CALIXARENES: TRENDS AND FUTURE
APPLICATIONS. Simon G. Bott,a,b* Julie A. Francis,b and Andrew R.
Barron,b* (a) Department of Chemistry, University of
Houston, Houston, Texas 77204, (b) Department of Chemistry, Rice
University, Houston, Texas 77005.
(1)
Continuing
investigations of the formation, structure and reactivity of aluminum
complexes of calixarenes will be presented. The structural control
exerted by the aluminum alkyl substituent is demonstrated through the
synthesis of an homologous series of compounds. The application of
these compounds to Ziegler-Natta catalysis will be discussed.
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- CLEAVAGE OF
DIALKYL-SILOXANES BY ALUMINUM HYDRIDES.
- C.
Niamh
McMahon,a Simon G. Bott,b and Andrew R. Barron,a*
(a)
Department of Chemistry, Rice University, Houston, Texas 77005 and
(b) Department of Chemistry, University of Houston, Houston, Texas
77024.
(I)
Reaction of cyclic
and linear siloxanes, (Me2SiO)n (n = 3, 4, 5), with R2AlH (R = tBu,
iBu) results in the cleavage of Si-O bonds via a hydride shift to the
Si and subsequent formation of an Al2O2 dimeric species, e.g., I.
These species react further with R2AlH. The reaction of RAlH2(L) with
(R2SiO)n is also detailed.
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- SUPRA-MOLECULAR
ALKYL-ALUMOXANES. Stephen J. Obrey, and Andrew
R. Barron,* Department of Chemistry,
Rice University, Houston, Texas 77005.
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- A new form of alkyl-alumoxane has been
prepared using the carboxylate substituted alumoxane
nano-particles as a template. These new alumoxanes have been
characterized by solid state and solution NMR spectroscopy. The
reactivity of these supra-molecular species will be discussed as
well as their relationship to the carboxylate and siloxide
alumoxanes previously reported.
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