Magnesium and zirconium Lewis acids for cooperative Lewis pair chemistry

An exploration of Lewis pair chemistry is contained within this thesis, with a particular focus on frustrated Lewis pair (FLP) type reactivity using Zr or Mg based Lewis acids in combination with a phosphine, amine, or pyridine base. Chapter 1 provides a background to both Zr and Mg chemistry where it relates to this work. Chapter 2 details the development of intermolecular Zr/N FLPs, employing two separate zirconocene species in combination with a selection of pyridine and amine Lewis bases. These were themselves analysed, before being reacted with a series of small molecules (D₂, CO₂, THF, and PhCCD), resulting in varying reactivity that is controlled by the steric and electronic properties of the Lewis base. Chapter 3 builds on this work by examining the catalytic capability of the same Lewis pairs through the dehydrocoupling of Me₂NH·BH₃, with activity shown to match or exceed that previously reported using phosphines in certain cases. Chapter 4 investigates intermolecular Lewis pair systems for small molecule activation (H₂, PhCCD, pentanone, benzaldehyde, and mesitaldehyde) using a novel Mg Lewis acid in combination with phosphines, pyridines, and amines, with limited success. However, more success was seen upon the use of the same Lewis pairs for the catalytic dehydrocoupling of Me₂NH·BH₃, especially upon an increase in reaction temperature to 60 °C-where activity of the Mg Lewis acid by itself approached that of Zr/P systems. Finally, Chapter 5 reports the synthesis of a novel intramolecular Mg/P Lewis pair, which was then tested for its small molecule activation (H₂, C₂H₄, CO₂, CD₂Cl₂, PhCCD, PhNCO, 3-pentanone, benzaldehyde, and mesitaldehyde) and catalytic capability (dehydrocoupling of Me₂NH·BH₃). The reactivity displayed gives an improved understanding of the steric and electronic environments necessary to achieve desired results, aiding in the design of future compounds.