Application of flow-based methods to inorganic materials synthesis

Controlling particularly reactive substances to achieve desired outcomes is a constant challenge in materials chemistry. Reactants and products consisting of main group and transition metal elements often exhibit extreme sensitivity to their environments. Therefore, it is desirable to develop new methods of synthesis and handling of the starting materials and resulting products in order to extend the chemical space available within this domain of science. Reactivity must be defined within the context of this dissertation. Herein, 'reactive' is exceptional sensitivity to air and moisture leading to degredation of reactants or desired products. Reactivity may also correspond to the explosive or pyrophoric nature of reactants and products inevitably preventing their isolation and handling under ambient conditions. Several observations which are pertinent to the fundamental understanding of the reactivity of various metalorganic, orgnaometallic, and main group complexes are chronicled within this dissertation. A comparison is provided for two methods (batch and flow) that are typically used to perform and control reactions. Due to the prevalence flow chemistry within my work, emphasis will be placed upon flow-based methods. In chapter 1, a short primer on fluid dynamics relevant to materials chemistry will be provided to compare and contrast batch versus flow chemistry. Examples of flow chemistry applied to organic reactions are given, followed by examples of inorganic chemistry in flow which is much less developed. Finally, the overarching goals of this work are as follows: 1) Present the basics of fluid dynamics to provide a basis for the flow chemical approaches within this work. 2) Provide a discussion of current flow-based methods applied to organic and inorganic synthesis. 3) To detail and study the application of flow chemistry techniques to the synthesis of new and existing metal organic, organometallic, and main group compounds and materials. In chapter 2, a simplified droplet generator is introduced and utilized to yield hollow silica capsules from a liquid--liquid interfacial polymerization reaction. Further use of this simple droplet generator is examined for preparation of SiO2-TiO2 hybrid capsules along with a cartridge-based method to modify the capsule surface with additional TiO2. In chapter 3, our growing interest in reactive materals led to the discovery that alkali metal oxides can be trapped and crystallized using diethlyzinc. From this observation, a family of complexes were isolated and characterized. Chapter 3 will also incoporate flow-based synthesis of organozinc complexes. First, the continuous preparation of organozinc halides is established and then coupled directly to Negishi reactions for the production of desirable building blocks for active pharmaceutical ingredients. Second, a catridge-based method for the utilzation of pyrophoric solid reagent Na2(HZnEt2)2 is presented leading to a series of novel organozincates. In chapter 4, the traditional methods used to synthesize alkali metal polyphosphides are discussed. Our discovery of solution-phase methods which allow facile access to homoatomic polyanions of phosphorus which do not involve harsh reducing alkali metals or the white allotrope of the element is detailed. We then demonstrate a high-throughput continuous-flow approach for rapid generation of gram quantities of these soluble polyphosphide anions.