A Super-Oxidized Radical Cationic Icosahedral Boron Cluster.

Area of Science:

• Inorganic Chemistry
• Electrochemistry
• Boron Cluster Chemistry

Background:

• The parent icosahedral closo-[B₁₂H₁₂]^2- cluster lacks reversible electrochemical behavior.
• Perfunctionalization with alkoxy or benzyloxy (OR) groups introduces reversible redox chemistry, enabling dianionic, monoanionic, and neutral states.

Purpose of the Study:

• To investigate the electrochemical behavior of the electron-rich B₁₂(O-3-methylbutyl)₁₂ (1) cluster.
• To explore the possibility of accessing new electronic states beyond the known dianionic, monoanionic, and neutral forms.

Main Methods:

• Electrochemical evaluation of B₁₂(O-3-methylbutyl)₁₂.
• Chemical oxidation using [N(2,4-Br₂C₆H₃)₃]^•+ to generate the cationic species.
• Characterization of the oxidized cluster using EPR, UV-vis, multinuclear NMR (¹H, ¹¹B), and XPS.

Main Results:

• A new reversible redox event was discovered, leading to a fourth electronic state via one-electron oxidation of the neutral cluster.
• The one-electron oxidized cluster, [1]^•+, was isolated and characterized.
• This represents the first example of an open-shell cationic boron cluster with proposed delocalization of the unpaired electron across the boron core.
• The oxidation process was shown to be chemically reversible.

Conclusions:

• Perfunctionalized boron clusters exhibit rich and tunable electrochemical properties.
• The discovery of the open-shell cationic B₁₂(O-3-methylbutyl)₁₂ cluster expands the known electronic states accessible for boron cages.
• This finding opens new avenues for exploring the chemistry and applications of boron clusters in various fields.