The trifluorophosphonium ion, PF3H+, preparation and structure

Area of Science:

• Inorganic Chemistry
• Solid-State Chemistry
• Computational Chemistry

Background:

• Protonation of phosphorus trifluoride (PF3) in strong acid media is a key reaction in inorganic synthesis.
• Understanding the structure and properties of novel cationic species is crucial for advancing chemical knowledge.

Purpose of the Study:

• To synthesize and characterize the PF3H+ ion.
• To determine the crystal structure of PF3H+SbF6-.HF.
• To investigate the vibrational spectra and computational properties of the PF3H+ ion and its deuterated analogue.

Main Methods:

• Protonation of PF3 using HF/SbF5 in anhydrous HF at low temperatures.
• Single-crystal X-ray diffraction for crystal structure determination.
• Raman spectroscopy and ab initio calculations for vibrational analysis.

Main Results:

• Successful preparation and isolation of PF3H+SbF6-.HF crystals.
• Crystal structure revealed a pseudo-tetrahedral PF3H+ ion with specific P-F and P-H bond distances and PF2 angles.
• Raman spectra of PF3H+ and PF3D+ were assigned using ab initio calculations.
• AsF3 did not react with HF/SbF5, while SF4 formed the isostructural SF3+SbF6-.HF.

Conclusions:

• The PF3H+ ion exists as a pseudo-tetrahedral species in the solid state.
• Ab initio calculations support the assignment of vibrational spectra.
• The reactivity of PF3 with HF/SbF5 differs from AsF3 and SF4, highlighting unique chemical behavior.