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Mono- and Bis(iminoxolene)iridium Complexes: Synthesis and Covalency in π Bonding
1Department of Chemistry and Biochemistry, University of Notre Dame, 251 Nieuwland Science Hall, Notre Dame, Indiana 46556-5670, United States.
Iridium complexes with N-(2,6-Diisopropylphenyl)-4,6-di-tert-butyl-o-iminobenzoquinone (Diso) ligands were synthesized. These complexes exhibit strong, covalent metal-π bonding, with significant iridium character in the orbitals.
Area of Science:
- Organometallic Chemistry
- Coordination Chemistry
- Inorganic Synthesis
Background:
- Exploration of metal-ligand interactions in novel coordination complexes.
- Investigation of iminobenzoquinone ligands in transition metal chemistry.
Purpose of the Study:
- To synthesize and characterize novel iridium complexes with iminobenzoquinone ligands.
- To investigate the electronic structure and bonding properties of these complexes.
- To explore the reactivity and stability of the synthesized iridium compounds.
Main Methods:
- Reaction of (cyclooctadiene)iridium chloride dimer and chlorobis(cyclooctene)iridium dimer with N-(2,6-Diisopropylphenyl)-4,6-di-tert-butyl-o-iminobenzoquinone (Diso).
- Synthesis of mono- and bis-iminoxolene iridium complexes.
- Structural characterization (X-ray crystallography) and spectroscopic analysis (NMR, UV-Vis).
- Redox studies involving reduction and oxidation of the complexes.
- Halide exchange reactions.
Main Results:
- Formation of mono- and bis-iminoxolene iridium complexes, including a five-coordinate (Diso)₂IrCl.
- The bis-iminoxolene complex exhibits a distorted square pyramidal structure and undergoes halide exchange to form a stable iodide complex.
- Redox chemistry yields neutral (Diso)₂Ir and octahedral trans-(Diso)₂IrCl₂.
- Structural and spectroscopic data indicate strong, covalent π bonding between iridium and iminoxolene ligands (45-60% Ir character).
- Comparison with cobalt congeners suggests similar covalent π bonding in first-row metal complexes.
Conclusions:
- Novel iridium-iminoxolene complexes were successfully synthesized and characterized.
- Strong covalent π bonding is a key feature of these metal-ligand interactions.
- The electronic structure and bonding are comparable to related first-row transition metal complexes.
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