Kai-Yao Wang

• Extensive studies on polyoxometalates (POMs), from synthesis to structural examination, have revealed a versatile structural evolution and its relevance to technological applications of these materials in green catalysis, medicine, magnetism, materials science, and molecular recognition, and so on. Lacunary (vacant) POMs can incorporate additional electrophiles from the p-, d-, and f-blocks by virtue of their exposed, reactive oxo ligands, resulting in products with enhanced structural and compositional diversity. Titanium(IV)-containing heteropolytungstates are highly interesting for their diverse structural chemistry as well as their catalytic properties. The Ti4+ ion fits well into the vacant addenda sites of various types of Keggin or Wells-Dawson heteropolytungstate precursors. The first part of this thesis is dedicated to the reaction of the [TiO]2+ cation and lone-pair containing, lacunary POM precursors of the type [α-XIIIW9O33]9- (X = As, Sb). This work has resulted in seven novel TiIV-containing heteropolytungstates. Lanthanide-containing heteropolyanions are of interest due to their highly diverse structural and chemical nature. Due to the large size of the lanthanide(Ln) ions they cannot be fully incorporated into lacunary heteropolyanions, and hence coordinate to several terminal water ligands, resulting in large coordination numbers and compounds with Lewis acidic properties. In the second part of this thesis the reactivity of lanthanide ions with trilacunary Keggin-type polyanions such as [a-XW9O34]10- (X = Si, Ge) has been investigated. This work has resulted in three novel LnIII-containing heteropolytungstates.