Identification of a Simplest Hypervalent Hydrogen Fluoride Anion in Solid Argon

Area of Science:

• Chemical Bonding
• Quantum Chemistry
• Molecular Spectroscopy

Background:

• Hypervalent molecules, exceptions to the octet rule, are typically explained by the Rundle-Pimentel model.
• High ionic bonding is considered essential for stabilizing hypervalent molecules.

Purpose of the Study:

• To produce and characterize the simplest hypervalent anion, hydrogen monofluoride anion (HF^-).
• To investigate the deviation of HF^- from the Rundle-Pimentel model.
• To determine the ro-vibrational features and bonding nature of HF^-.

Main Methods:

• Production of the HF^- anion.
• High-level ab initio calculations for electronic structure and bonding.
• Secondary photolysis experiments with variable wavelength irradiation.
• Charge distribution analysis.

Main Results:

• The HF^- anion was successfully produced and its ro-vibrational features identified.
• Ab initio calculations showed bond dissociation energy comparable to dihalides.
• Charge distribution analysis indicated a hypervalent fluorine atom with more covalent than ionic bonding.

Conclusions:

• HF^- deviates from the standard Rundle-Pimentel model for hypervalent bonding.
• The bonding in HF^- is characterized by significant covalent character, challenging the necessity of high ionic bonding for stability.