Advances in the development, evaluation, and application of weakly coordinating cations

Abstract

Weakly-coordinating ions are ions that have reduced interactions with their counterion. Weakly-coordinating anions are a well-established phenomenon, whereas weakly-coordinating cations (WCCs) are comparatively understudied. Commonly used WCCs have drawbacks such as the ability to act as hydrogen bond donors or incompatibility with basic anions. There is a need to develop improved WCCs that overcome the limitations of those currently in use, as well as to establish methods by which the coordination behavior of WCCs can be quantified. This work has furthered the study of WCCs in both of these areas with the investigation of electron-donating group substituted tetraarylphosphonium cations and decaarylcobaltocenium cations as candidates for improved WCCs and with the development of an Ultraviolet-Visible spectroscopy-based method for the evaluation of cation coordination behavior. Charge-enhanced organocatalysts have been demonstrated to show significantly increased catalytic activity compared to neutral organocatalysts and have been a focus of our research group over the past ten years, with a multitude of charge-enhanced acidic and basic organocatalysts having been developed. My second research area involved the application of WCCs to charge-enhanced anionic organocatalysts by examining the relationships between their solid-state structures and solution state reactivities.