Non-Coordinated Phenolate Anions and Their Application in SF6 Activation.
Robin F Weitkamp1, Beate Neumann1, Hans-Georg Stammler1
1Centrum für Molekulare Materialien, Fakultät für Chemie, Universität Bielefeld, Universitätsstraße 25, 33615, Bielefeld, Germany.
Chemistry (Weinheim an Der Bergstrasse, Germany)
|August 11, 2020
Summary
Researchers created the first free phenolate anion salt using a powerful tetraphosphazene base. This new phosphazenium phenolate salt can activate the greenhouse gas sulfur hexafluoride (SF6).
Area of Science:
- Organometallic Chemistry
- Supramolecular Chemistry
- Green Chemistry
Background:
- Strong bases are needed to deprotonate weakly acidic phenols.
- Previous methods often resulted in hydrogen-bonded phenol-phenolate species.
- Isolation of truly free phenolate anions has been challenging.
Purpose of the Study:
- To synthesize and characterize a novel salt containing a free phenolate anion.
- To investigate the utility of tetraphosphazene bases for phenolate salt preparation.
- To explore the reactivity of the synthesized phosphazenium phenolate salt, specifically its ability to activate SF6.
Main Methods:
- Reaction of phenol derivatives with a tetraphosphazene base (Schwesinger base).
- Isolation and characterization of the resulting phosphazenium phenolate salt.
- Electrochemical studies to determine redox potential.
- Investigation of the reaction with sulfur hexafluoride (SF6).
Main Results:
- Successfully synthesized the first isolable salt featuring a free phenolate anion ([H5C6-O]-).
- The phosphazenium phenolate salt exhibits a redox potential of -0.72 V.
- The salt selectively activates the greenhouse gas SF6 through a two-electron reduction, yielding pentafluorosulfanide ([SF5]-) and fluoride salts.
Conclusions:
- Tetraphosphazene bases are highly effective for the clean synthesis of free phenolate anions.
- This work provides a new route to selective synthesis of hydrogen-bonded phenol-phenolate salts.
- The synthesized phosphazenium phenolate salt demonstrates potential for activating inert gases like SF6, offering new avenues in catalysis and chemical activation.
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