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Mesoionic Carbenes in Low- to High-Valent Vanadium Chemistry
Florian R Neururer1, Shenyu Liu2, Daniel Leitner1
1Institute of Inorganic, General and Theoretical Chemistry, University of Innsbruck, Innrain 80-82, 6020 Innsbruck, Austria.
Inorganic Chemistry
|September 30, 2021
Summary
Mesoionic carbene (MIC) ligands stabilize vanadium complexes across multiple oxidation states, challenging previous assumptions. These findings highlight MICs as promising for small molecule activation and redox catalysis.
Area of Science:
- Organometallic Chemistry
- Coordination Chemistry
- Catalysis
Background:
- Mesoionic carbene (MIC) ligands are emerging as versatile ligands in organometallic chemistry.
- Their electronic properties and coordination behavior with early transition metals are less explored.
- Vanadium complexes are relevant in catalysis and redox processes.
Purpose of the Study:
- To synthesize and characterize novel vanadium(V) oxo complexes featuring a pincer-type dianionic MIC ligand.
- To compare the properties of MIC-vanadium complexes with benzimidazolinylidene congeners.
- To investigate the potential of MIC ligands in supporting various vanadium oxidation states for catalytic applications.
Main Methods:
- Synthesis of vanadium(V) oxo complexes with MIC ligands.
- Structural characterization using single-crystal X-ray diffraction (SC-XRD).
- Electronic and electrochemical studies including UV-vis spectroscopy and cyclic voltammetry.
- Computational methods for electronic structure analysis.
- Reactions including salt metathesis, deoxygenation, and oxidation with organic azides.
Main Results:
- Successful synthesis of vanadium(V) oxo complex [VOCl(L1)] and its benzimidazolinylidene congener [VOCl(L2)].
- MIC ligand demonstrated stronger donor character compared to benzimidazolinylidene, even for early transition metals.
- Reversible reduction of vanadium(V) to vanadium(IV) was observed and characterized.
- Complex [VOCl(L1)] showed selective reactivity in salt metathesis reactions.
- Vanadium(III) and imido complexes were successfully synthesized, showcasing MIC ligand stability across oxidation states.
Conclusions:
- Mesoionic carbene ligands can effectively stabilize early transition metal complexes in various oxidation states.
- Contrary to prior beliefs, MICs are suitable for supporting diverse vanadium oxidation states, including V(V), V(IV), and V(III).
- These findings establish MIC-vanadium complexes as promising candidates for small molecule activation and redox catalysis.
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