Structural and spectroscopic studies of fluoroprotactinates

Area of Science:

• Inorganic Chemistry
• Solid-State Chemistry
• Coordination Chemistry

Background:

• Protactinium(V) fluoride chemistry is underexplored, with limited structural data available.
• Understanding the coordination environment and structural motifs of protactinium complexes is crucial for its chemical characterization.

Purpose of the Study:

• To synthesize and characterize novel protactinium(V) fluoride compounds.
• To elucidate the crystal structures and coordination geometries of these new compounds.
• To investigate the speciation of protactinium(V) in aqueous hydrofluoric acid solutions.

Main Methods:

• Single-crystal X-ray diffraction for crystal structure determination.
• Raman spectroscopy for vibrational analysis in solid and solution states.
• Synthesis of various alkali metal and ammonium/tetramethylammonium fluoroprotactinates.

Main Results:

• Seven protactinium(V) fluoride compounds were successfully synthesized.
• Structures reveal nine-coordinate and eight-coordinate protactinium centers with diverse coordination environments, including infinite chains and molecular species.
• Raman spectra suggest the PaF8(-) anion is prevalent in concentrated aqueous HF.

Conclusions:

• The synthesis and structural characterization of seven protactinium(V) fluorides expand the known structural diversity of this element.
• The study provides insights into the coordination preferences of protactinium(V) in fluoride media.
• The PaF8(-) anion is proposed as a significant species in protactinium(V) solutions in hydrofluoric acid.