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Green Oxidation Catalysts Synthesis of a catalyst for environmentally benign oxidation by N2O Addie

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Previously Known N2O-Activating Complexes Involving Ni. Hillhouse published a Ni complex that reacted with N2O and activated the O atom. ... – PowerPoint PPT presentation

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Title: Green Oxidation Catalysts Synthesis of a catalyst for environmentally benign oxidation by N2O Addie


1
Green Oxidation Catalysts Synthesis of a
catalyst for environmentally benign oxidation by
N2O Addie Summitt and Megumi FujitaDepartment
of Chemistry, University of West Georgia,
Carrollton, GA 30118
  • Acknowledgments
  • GEMS Summer Research Program
  • National Science Foundation STEP grant
    DUE-0336571
  • Amna Ali, a senior research student

Catalyst Design
1H NMRs
Introduction

Nickel was selected as a central metal ion
because of the previous example by Hillhouse that
showed N2O activation by a Ni complex. The
catalyst is made up of a bulky tridentate ligand
around a metallic center, in this case a Ni
center. It was proposed that activation of
nitrous oxide requires two coordination sites
next to each other. This ligand allows three
available coordination sites, two of which may be
used for N2O activation. Another advantage is
the overall -2 ligand charge, which neutralizes
the central metal ion. This will create an
overall neutral metal complex which is compatible
with organic reaction media.
Ligand in CD3CN (burnt orange)
Nitrous oxide is a very destructive greenhouse
gas released by many industrial waste sites
however, in the presence of a well designed metal
catalyst, this gas has the potential to be an
oxidation reagent. This potential oxidation by
N2O could be exploited in many industrial
oxidation processes as an environmentally
friendly alternative because the only byproduct
of the oxidation would be an environmentally
benign N2 gas. The use of such a catalyst in
industries would contribute to the reduction of
N2O into the environment, which in turn would
help reduce the destruction of the Earths ozone
layer. Our research goal is to develop a
transition metal catalyst to activate N2O and
mediate in the oxygen atom transfer to an organic
substrate.
NH
Ligand 2NaH in CD3CN (brown)
tentatively assigned as Na salt of ligand
(u) unknown impurity
Mechanism of N2O Activation
Ligand Synthesis

No NH peak deprotonation complete




(u)



The first step in the N2O activation is to have
a ligand with a metal center (our catalyst) take
the oxygen atom from the N2O. The catalyst then
acts as the oxidizing agent as it transfers the
oxygen to a gas like CH4. A good catalyst would
be able to repeat this cycle over and over again.
(u)
(u)
(u)
(u)
Ni Complexation in CD3CN (dark purple)
new species (Ni complex?)
(s) starting ligand

(s)
(s)
(s)






(s)
(s)

Previously Known N2O-Activating Complexes
Involving Ni Hillhouse published a Ni complex
that reacted with N2O and activated the O atom.
(s)
(s)
Pure crystals were obtained from ethyl acetate
as 11 co-crystals with the solvent, confirmed by
elemental analysis.
The yield of each step has been improved by
optimizing the reaction, workup, and purification
conditions. This is the first time our lab
produced this ligand in a large (2 g) scale,
which allows us to explore metal complexation
chemistry.
Attempts for Crystallization
Ni Complexation
After a solubility test in toluene, diethyl
ether, and hexanes, a crystallization attempt of
the Ni Complexation was done with toluene-
hexanes two solvent method toluene being the
good solvent and hexanes being the poor solvent.
Conclusion and Future Work

The synthesis reactions conducted thus far have
been very successful. Future work includes
having a successful reaction between the
tridentate ligand and NiCl2, and then testing the
catalyst for catalytic behavior.
However, the complex resulted in internal
oxidation, and was not catalytic.
Overall reaction took about 3 days.
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