Investigations into the Reactivity and Structure of Phosphinophosphonium Cations and Related Species

Abstract

Carbon and phosphorus have often been compared owing to their diagonal relationship on the periodic table. However, relative to carbon, there remains an enormous breadth of polyphosphorus chemistry that is unexplored, particularly in the area of cationic phosphorus. A key step in the systematic and rational development of larger catenated organo-polyphosphorus cations is a fundamental understanding of the reactivity of small cationic building blocks. The smallest catenated framework in this context is the phosphinophosphonium monocation [R3P-PR2]+ (or phosphine-stabilized phosphenium cation), which can be prepared with a variety of functional groups at either phosphorus centre. This dissertation explores the diverse reactivity of chloro-substituted phosphinophosphonium cations, with a particular focus on reductive coupling as a synthetic route to novel catena-phosphorus systems. The resulting cationic frameworks are comprehensively described in terms of their diasteroisomerism, solution dynamics, and solid-state structural features. Additionally, fundamental electrochemical investigations of these diphosphorus cations are outlined as a tool for understanding and quantifying the reactivity of phosphenium cations. Finally, extension of reductive coupling methodology to the first chlorostibinophosphonium cations presents a promising outlook towards the catenation of the heavier pnictogen cations.