Solid state and mechanistic study on pyrone based complexes of early, middle and platinum group transition metal elements
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Date
2018-02
Authors
Molokoane, Pule Petrus
Journal Title
Journal ISSN
Volume Title
Publisher
University of the Free State
Abstract
3-Hydroxypyrones and their corresponding analogues 3-hydroxypyridinones are a versatile class
of chelators. The commercially available pyrones: 3-hydroxy-2-methylpyran-4-one (1) and 3-
hydroxy-2-ethylpyran-4-one (2) were functionalised to yield the respective 3-hydroxy-2-
methylpyrid-4-one (3) and 3-hydroxy-2-ethylpyrid-4-one (4) derivatives. These ligands were
coordinated to an array of metals, divided broadly into three groups: early, middle and platinum
group transition metals, to form the corresponding metal complexes. A total of eight bidentate
ligands with different electronic and steric properties were used in this study. These ligands and
the corresponding complexes are explored as models for: (i) the potential beneficiation of
hafnium and zirconium for the nuclear industry, (ii) the application as model complexes for
diagnostic and therapeutic radiopharmaceuticals in studies using the fac-[ReI(CO)3]+ core and
(iii) rhodium(I) homogeneous catalysts for oxidative addition reactions. In all of the respective
sub-sections of this study, the structural characterisation of crystalline products of the above
mentioned compounds were extensively evaluated by means of single crystal X-Ray Diffraction
(XRD). This study therefore covers a detailed structural discussion of the analysis and
comparison with similar Zr(IV), Hf(IV), Re(I) and Rh(I) compounds which could yield valuable
insights into physical and/or chemical state differences to be exploited for purification/separation
techniques, diagnostic and therapeutic endeavours and catalytic processes respectively. Finally,
structure/ reactivity relationships were attempted to assist in the future prediction of relevant
characteristics of these compounds. A kinetic evaluation on fac-[ReI(O,O’-bid)(CO)3(Y)] (O,O’-
bid = O,O’-bidentate ligand and Y = monodentate ligand) substitution reactions with
monodentate chelators in methanol, indicated a possible dissociative activated methanol
substitution mechanism in these types of complexes and that these substitutions are solvolytic in
nature.
Description
Keywords
3-Hydroxypyrones, 3-Hydroxypyridinones, 3-Hydroxy-2-methylpyran-4-one, 3-Hydroxy-2-methylpyrid-4-one, 3-Hydroxy-2-ethylpyrid-4-one, Beneficiation, Diagnostic, Therapeutic, Radiopharmaceuticals, Rhodium(I) homogeneous catalysts, XRD and kinetics, 3-Hydroxy-2-ethylpyran-4-one, Thesis (Ph.D. (Chemistry))--University of the Free State, 2018