Doctor of Philosophy / Department of Chemistry / Stefan Bossmann / My thesis is divided into two parts. The first part is focused on studies of N-heterocyclic
carbene (NHC) palladium(IV) intermediates, which are involved in oxidative addition mediated
C-C, and C-O bond formation processes as well as in C-Cl bond forming reactions via a
reductive elimination process. Bis-NHC-Pd(II) complexes have been reported as effective
catalysts to mediate direct conversion of methane into methanol. However, a H-D exchange
study revealed that the bis-NHC-Pd(II) complexes are not the active species responsible for the
C-H bond activation reaction. This unexpected result implies that the high oxidation state bis-
NHC-Pd(IV) species may be the real catalyst! The oxidative addition of methyl iodide to the bis-
NHC-Pd(II)-Me2 complex led to the successful observation of the formation of a transient
trimethyl bis-NHC-Pd(IV) intermediate by both 1H-NMR and 13C-NMR spectroscopy. Different
oxidants such as O2, PhI(OAc)2, PhI(OTFA)2 and Cl2 reacted with the bis-NHC-Pd(II)-Me2
complex, and competitive C-C and C-O bond formations, as well as C-C and C-Cl bond
formations were observed. Dioxygen triggered C-C bond formation under dry condition and both
C-C and C-O bond formation in the presence of H2O gave strong indications that the bis-NHCPd(
II)-Me2 complex can be oxidized to a bis-NHC-Pd(IV) intermediate by dioxygen. The
reaction between the hypervalent iodine regents PhI(OAc)2 and PhI(OTFA)2 and the bis-NHCPd(
II)-Me2 complex gave only reductive elimination products. Therefore, this system can act as a
model system, which is able to providing valuable information of the product forming
(functionalization) step of the C-H bond activation system. The reaction between chlorine and
the bis-NHC-Pd(II)-Me2 complex resulted in a relatively stable bis-NHC-Pd(IV)-Cl4 complex,
which was characterized by 1H-NMR spectroscopy and mass spectroscopy. The structure of bis-
NHC-Pd(IV)-Cl4 was unambiguously established by X-ray crystallography.
The second part of this thesis describes the synthesis of functionalized bimagnetic
core/shell iron/iron oxide nanoparticles for the treatment of cancer. Biocompatible dopamineoligoethylene
glycol functionalized bimagnetic core/shell Fe/Fe3O4 nanoparticles were prepared
via ligand exchange, and purified by repeated dispersion/magneto-precipitation cycles. A
porphyrin (TCPP) has been tethered to the stealth nanoparticles to enhance their uptake by tumor
cells and (neural) stem cells. The stealth nanoparticles have been delivered in a mouse model to
tumor sites intravenously by using the EPR (enhanced permeation and retention) effect. Magnetic hyperthermia proved to be very effective against B16-F10 mouse melanomas in
Charles River black mice. After hyperthermia, the nanoparticles have shown a significant effect
on the growth of tumor (up to 78% growth inhibition).
| Identifer | oai:union.ndltd.org:KSU/oai:krex.k-state.edu:2097/7510 |
| Date | January 1900 |
| Creators | Wang, Hongwang |
| Publisher | Kansas State University |
| Source Sets | K-State Research Exchange |
| Language | en_US |
| Detected Language | English |
| Type | Dissertation |
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