Solid state and mechanistic study on pyrone based complexes of early, middle and platinum group transition metal elements

[摘要] 3-Hydroxypyrones and their corresponding analogues 3-hydroxypyridinones are a versatile classof 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 werecoordinated to an array of metals, divided broadly into three groups: early, middle and platinumgroup transition metals, to form the corresponding metal complexes. A total of eight bidentateligands with different electronic and steric properties were used in this study. These ligands andthe corresponding complexes are explored as models for: (i) the potential beneficiation ofhafnium and zirconium for the nuclear industry, (ii) the application as model complexes fordiagnostic 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 respectivesub-sections of this study, the structural characterisation of crystalline products of the abovementioned compounds were extensively evaluated by means of single crystal X-Ray Diffraction(XRD). This study therefore covers a detailed structural discussion of the analysis andcomparison with similar Zr(IV), Hf(IV), Re(I) and Rh(I) compounds which could yield valuableinsights into physical and/or chemical state differences to be exploited for purification/separationtechniques, diagnostic and therapeutic endeavours and catalytic processes respectively. Finally,structure/ reactivity relationships were attempted to assist in the future prediction of relevantcharacteristics 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 withmonodentate chelators in methanol, indicated a possible dissociative activated methanolsubstitution mechanism in these types of complexes and that these substitutions are solvolytic innature.

[发布机构] University of the Free State