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Ligand-ligand redox interaction through some metal-cluster units
1Division of Chemistry, Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan. ysasaki@sci.hokudai.ac.jp
Chemical Record (New York, N.Y.)
|November 16, 2004
Summary
Ligand-ligand redox interactions are observed in multinuclear metal clusters, not mononuclear complexes. Empty pi orbitals are crucial for this communication in mixed-valence states.
Area of Science:
- Inorganic Chemistry
- Electrochemistry
- Materials Science
Background:
- Investigating redox interactions between ligands in metal complexes is key to understanding electron transfer.
- Mononuclear complexes often exhibit independent ligand redox behavior.
Purpose of the Study:
- To explore ligand-ligand redox interactions mediated by di-, tri-, and hexanuclear cluster units.
- To analyze the influence of metal cluster size and electronic structure on redox wave splitting and comproportionation.
Main Methods:
- Electrochemical analysis of mononuclear ruthenium(II) complexes and multinuclear clusters.
- Evaluation of redox wave splitting (DeltaE(L)) and comproportionation constants (Kcom(L)).
- Molecular orbital considerations to interpret electronic communication pathways.
Main Results:
- Mononuclear complexes showed no significant redox wave splitting for ligands.
- Triruthenium and hexarhenium clusters facilitated clear splitting of ligand reduction waves, indicating interaction.
- Absence of interaction in oxo-bridged diruthenium and trirhodium complexes highlighted the role of empty pi* orbitals.
Conclusions:
- Multinuclear cluster units enable ligand-ligand redox communication, unlike mononuclear systems.
- The presence of empty pi-type molecular orbitals within cluster units is essential for mediating these interactions.
- Ligand redox communication is dependent on the availability of empty antibonding pi orbitals (pi*) for electron delocalization.