Bis(catecholato)telluranes: Probing Catecholato-Induced Hard Lewis Acidity via Redox-Coupled Halide Abstraction

Area of Science:

• Organotellurium chemistry
• Main group chemistry
• Lewis acid-base interactions

Background:

• Bis(catecholato)telluranes (BCTs) are an underexplored class of chalcogen-based compounds.
• Understanding their Lewis acidity and anion-binding properties is crucial for developing new chemical reagents.

Purpose of the Study:

• To investigate the Lewis acidity, anion-binding, and redox behavior of unsubstituted, perchloro-, and perbromo-BCTs.
• To elucidate the mechanism of SbF₆^- activation by BCTs.

Main Methods:

• Experimental techniques including Gutmann-Beckett analysis, ¹²⁵Te NMR, ¹⁹F NMR, HRMS, and cyclic voltammetry.
• Computational methods such as fluoride ion affinity (FIA) calculations.

Main Results:

• Perchloro- and perbromo-BCTs exhibit comparable Lewis acidic strengths.
• A BCT was observed to defluorinate SbF₆^-, forming a tellurium-fluoride adduct, despite lower calculated FIA values.
• Redox processes involving catecholato ligands and a proposed fluoride-coupled electron transfer (FCET) mechanism were identified for SbF₆^- activation.
• Strong covalent interactions with fluoride and chloride ions were confirmed, indicating a hard Lewis acidic nature.

Conclusions:

• Perhalogenated BCTs possess significant Lewis acidity and unique reactivity towards fluoroanions.
• The observed defluorination suggests a novel FCET mechanism for SbF₆^- activation.
• BCTs demonstrate potential as versatile reagents in anion binding and redox chemistry.