Doctor of Philosophy
Ragogna, Paul J.
In recent years, the field of low-coordinate main group chemistry has seen significant research interest due to their unique structures and unprecedented reactivity. Conversely, the area of phosphinidene chalcogenides, a low-coordinate phosphorus and chalcogen species, have yet to be thoroughly explored. In this context, this dissertation describes the synthesis of a number of phosphorus-chalcogen heterocycles that can be degraded to provide stoichiometric access to low-coordinate phosphorus species. The ability for successful P-Ch transfer relies on using a bulky m-terphenyl group at phosphorus that provides enough steric bulk to kinetically stabilize the phosphorus centre, but also accommodating enough to allow for further reactivity. Previous attempts at this chemistry have utilized more sterically accommodating ligands, however sterically demanding ligands have now been proven to be critical in controlling the fragmentation and transfer of these generated species. In Chapter 2, the synthesis of strained P-Ch heterocycles containing a 4-membered core will be discussed, as well as attempts to use these cyclic structures to gain access to low-coordinate phosphinidene chalcogenides. Chapter 3 continues from the success discussed in the previous chapter, and uses these newly generated rings as P-Ch transfer reagents for their reactions with alkynes. An alternative method of generating phosphinidene chalcogenides that mitigates the synthesis of P-Ch heterocycles will also be discussed. Chapter 4 explores the reactivity of these 4-membered rings using Lewis acids and bases, and again linking these compounds to the monomeric phosphinidene chalcogenides. Chapter 5 introduces the idea of combining two different low-coordinate phosphorus compounds (both generated from their parent dimer heterocycles) to generate a new heterocycle containing elements from Group 13, 15 and 16. The highlight of this thesis is discovering new methods of generating, and trapping phosphinidene chalcogenides. While the sulfur derivatives have been discussed in the literature, the chemistry surround the selenium compounds are unprecedented and include some of the first structural confirmation of such species. All of the compounds discussed in this thesis were characterized to the fullest extent using a range of solution and solid-state techniques, with an emphasis on NMR spectroscopy and single crystal X-ray crystallography.
Graham, Cameron, "Exploring the Synthesis, Structure, and Reactivity of Phosphorus-Chalcogen Heterocycles" (2018). Electronic Thesis and Dissertation Repository. 5258.