Photoactivated catalysts for the hydrosilylation of silanes and alkenes offer spatial and temporal control in manufacturing processes that require silicone curing. This thesis presents the development of a series of Pt(II) (salicylaldimine)(phenylpyridine) [Pt(sal)(ppy)] complexes as photoactivated hydrosilylation catalysts.
Chapter two outlines the rationale behind the design and synthesis of the [Pt(sal)(ppy)] complexes 1a–1g as latent precatalysts for photoactivated hydrosilylation. The key spectroscopic and structural features are presented to link the molecular structure to the catalytic performance.
Chapter three presents the development of a model hydrosilylation reaction that serves as a platform for probing reaction kinetics and mechanistic details using in situ 1H NMR spectroscopy. The utilisation of complexes 1a–1g as precatalysts in the model reaction under both thermal and photoactivated conditions is explored, and the structure of the phenylpyridine and salicylaldimine ligands is correlated with the catalytic activity. Many of these precatalysts were found to show excellent thermal latency and rapid (10 s) activation upon exposure to UV-light. Through a systematic examination of different alkene substrates, this chapter also elucidates the impact of substrate structure on the catalytic activity and selectivity when using precatalyst 1b. This chapter concludes by showcasing the ability of several precatalysts to cure the industrially used siloxane polymer substrates, highlighting their practical application.
In chapter four, the mechanistic intricacies of photoactivated hydrosilylation reactions using precatalysts 1a and 1b are investigated. Through a combination of poisoning experiments, kinetic studies, isotope labeling experiments and kinetic modelling, a mechanism is proposed based on an active homogeneous catalyst where reductive elimination is the turnover limiting step.
Chapter five outlines the key conclusions and potential directions for further exploration, and chapter six contains all experimental information.
