Excepting agricultural based products, which themselves require a great deal of
energy to produce, our supply of natural resources such as minerals, metal ore, fresh
water, coal, oil and natural gas are all limited in supply. The depletion of these
substances is imminent and this knowledge weighs heavily on humankind. The
utilization of CO2 for the production of polycarbonates is one attempt at exploiting a
profoundly abundant and renewable resource. The importance of research in this and
similar fields justifies the detailed study of the chemicals and procedures involved with
this chemistry. This current work concentrates on the fundamental study of transition
metal Schiff base complexes that have shown a great deal of promise in their ability to
catalyze the copolymerization of CO2 and epoxide to form aliphatic polycarbonates.
A new chromium(III) Schiff base complex has been synthesized and evaluated
for its ability to catalyze the formation of polymer. The ligand employed bears an N2O2
coordination sphere identical to the widely utilized chromium(III) and cobalt(III) salen
catalysts. This complex was shown to be active towards the copolymerization of CO2 and cyclohexene oxide. Although the activity was less than that seen with
chromium(III) salen complex, the study demonstrates that new ligand systems are
available beyond salen and deserve further attention.
A class of manganese(III) Schiff base complexes was also synthesized and
evaluated as catalysts. Although crystallographic data has shown that these complexes
are structural analogs to chromium(III) salens, the difference in metal center leads to a
nearly complete elimination of catalytic activity. Such a marked difference has been
taken advantage of by using this very low activity to study the ring-opening of epoxide
in the initial step of the copolymerization both mechanistically and kinetically. It has
also been utilized in an evaluation of the coordination chemistry of the polymerization
process. This has led to some valuable conclusions about the nature and role of the
metal center that previously have not been studied. Manganese(III) salen complexes
were also synthesized and evaluated in an effort to compare these important ligands to
other Schiff bases and confirm the findings mentioned above.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2893 |
| Date | 15 May 2009 |
| Creators | Frantz, Eric Benjamin |
| Contributors | Darensbourg, Donald J. |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | electronic, application/pdf, born digital |
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