Proton Coupled Electron Transfer at Heavy Metal Sites

by Daniel Delony
Doctoral thesis
Date of Examination:2020-12-10
Date of issue:2021-01-14
Advisor:Prof. Dr. Sven Schneider
Referee:Prof. Dr. Franc Meyer
Referee:Prof. Dr. Max C. Holthausen
Persistent Address: http://dx.doi.org/10.53846/goediss-8400

 

 

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Abstract

English

Terminal, late transition metal, oxo complexes are pivotal intermediates in oxygenation chemistry. This thesis describes the synthesis and full characterisation of an open-shell terminal oxo complex of iridium from the respective iridium(II) hydroxo complex by proton coupled electron transfer (PCET). Electronic examinations of the compound support high oxyl radical character and reactivity studies reveal nucleo- to ambiphilic character of the iridium oxo moiety. Calorimetric determination of the O-H bond dissociation free energy reveals a bond strength sufficient for the activation of C-H bonds. Additionally, computational analysis reveals a small thermochemical contribution of spin-orbit-coupling (SOC) on the O-H bond strength, even though SOC effects on thermochemistry are mostly assumed to be negligible in solution thermochemistry. The effect of SOC on heavy metal PCET chemistry is further investigated on the example of a rhenium(III) amine complex forming the corresponding rhenium(IV) amide. By combination of spectroscopy, magnetometry, isothermal titration calorimetry and high-level ab initio computations a large SOC effect of several kcal/mol on the PCET thermochemistry is revealed.
Keywords: Spin-Orbit-Coupling; Coordination Chemistry; Terminal Iridium Oxo; Proton-Coupled Electron Transfer; Iridium Pincer Complexes; Benchmarking; Rhenium Pincer Complexes
 
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