Transient and Stable Terminal Imido Complexes of Iridium

by Markus Kinauer
Doctoral thesis
Date of Examination:2019-03-26
Date of issue:2019-07-02
Advisor:Prof. Dr. Sven Schneider
Referee:Prof. Dr. Sven Schneider
Referee:Prof. Dr. Franc Meyer
Persistent Address: http://dx.doi.org/10.53846/goediss-7490

 

 

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Abstract

English

In conclusion, it has been demonstrated that the proton coupled oxidation of metal-bound amines and water provide access to a wide range of imido- and oxo-complexes, respectively. The synthetic approach of using strict 1 e- / 1 H+ abstraction reagents for an overall 2 e- / 2 H+ process paves the way for possible electrochemical synthesis of a nitrene/oxo building block. Because of the possibility of using a basic aqueous solution, the oxo complex is predestined for electrochemistry. The spectroscopic, magnetic, crystallographic and computational characterization of an iridium(III/IV/V) imido redox series is in line with highly covalent Ir–NtBu bonding as expressed by the simple MO model shown in . The dicationic complex of this series is purely diamagnetic. The data supports an electronic doublet ground state for the cationic imide with cylindrical delocalization of the spin density perpendicular to the Ir–NtBu bond as a result of SOMO/LUMO mixing through SOC. The neutral imide is best described as an electronic triplet with a separated non-magnetic ground state, which results in ambiphilic nitrene transfer reactivity with both CO2 and PMe3, amongst other reactions. In comparison, the chemical inertness of this compound is surprising and somewhat contradictive to the widely accepted assumption that radical character features enhanced reactivity. Besides steric shielding, this finding can be attributed to stabilizing relativistic contributions by SOC-induced spin delocalization, which moderates the reactivity of this class of electron-rich heavy metal imido complexes.
Keywords: Iridium; Imido; Triplet Ground State; 5d metal triplet ground state
 
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