A time-resolved infrared spectrosopy-led mechanistic study into manganese carbonyl catalysed C−H bond functionalisation reactions Jonathan Eastwood 1 , Thomas Burden 1 , Ian Clark 2 , Ian Fairlamb, 1 Gregory Greetham 2 , Anders Hammarback 1 , Jason Lynam, 1 Igor Sazanovich 2 , Michael Towrie 2 . 1 University of York, UK, 2 STFC Rutherford Appleton Laboratory, UK Manganese is a versatile, Earth-abundant first row transition metal, with significant potential as a catalyst in synthetically relevant transformations. [1-2] Over the past decade, recent advances in Mn(I)-catalysed C−H bond functionalisation reactions have provided synthetically useful methodologies that previously were limited to the platinum group metals. [3] In this work we describe how vibrational spectroscopy can be used to investigate precatalyst activation, carbon−carbon bond forming steps, and potential routes for catalyst deactivation. In situ IR spectroscopy and ultrafast time-resolved IR spectroscopy have been used to probe the critical mechanistic events discussed above on a scale of picoseconds through to hours. This presentation will focus on how ultrafast time- resolved IR spectroscopy can be applied to study catalytically relevant conditions. For the first time, the route of activation for one of the most ubiquitous manganese carbonyl precatalysts, [Mn 2 (CO) 10 ], has been established. Events were observed following photochemical, thermal, and chemically induced dissociation of a CO ligand, resulting in coordination of catalytically relevant ligands. Directed C−H bond activation then occurs, forming a 5-membered metallacycle. Upon further loss of a CO ligand, the coordination, then migratory insertionof catalytically relevant alkynes leads towards entry into the catalytic cycle. In addition, competitive coordination of dinitrogen and water were observed, forming a novel manganese dinitrogen complex. [4] References 1. Y. Hu, B. Zhou, C. Wang , Acc. Chem. Res ., 2018, 51 , 816-827. 2. W. liu, L. Ackermann, ACS Catal .2016, 6 , 3743–3752. 3. R. He, Z. Huang, Q. Zheng, C. Wang, Angew. Chem. Int. Ed ., 2014, 53 , 4950-4953. 4. J. Eastwood, L. A. Hammerback, M. T. McRobie, I. P. Clark, M. Towrie, I. J. S. Fairlamb, J. Lynam et al ., Dalton Trans ., 2020, 49 , 5463-5470.
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