The mechanistic investigation of transition metal catalyzed reactions has previously mainly been limited to time-averaged techniques, including in situ monitoring and kinetic analysis. Only the more stable intermediates can be observed, and the reaction kinetics give an averaged reflection of the reaction. In order to combat these limitations, we have developed a time-resolved in situ infra-red method to directly observe short-lived reaction intermediates over a broad temporal range (ps–ms). Central to the success of this approach has been the use of light to simulate thermal activation of a metal catalyst. We have studied manganese(I)-catalyzed C–H functionalisation reactions, where manganese is a versatile, earth abundant first row transition metal. Recent advances in Mn(I)-catalysed C–H bond functionalisation reactions have provided synthetically useful methodologies that previously was limited to the platinum group metals. We have employed our time-resolved spectroscopic method to observe the individual steps within the Mn(I)-catalytic cycle. An evaluation of the reaction kinetics of the individual steps has allowed for the factors controlling carbon-carbon bond formation (e.g. nature of the metal complex and substrate) to be quantified. We have also been able to expand the scope of the study, to observe other key organometallic intermediates and directly probe well established transition metal catalyzed mechanisms.

Mapping out the mechanism of Mn(I)-catalysed C–H bond functionalisation

2019 Spring National Meeting

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