Isolation and Structural Determination of a Hexacoordinated Antimony(V) Dication

Area of Science:

• Organometallic Chemistry
• Coordination Chemistry
• Antimony Chemistry

Background:

• Hexacoordinated antimony(V) complexes are rare and their structural characterization is limited.
• Understanding the coordination preferences and stability of antimony(V) species is crucial for developing new materials and catalysts.

Purpose of the Study:

• To synthesize and characterize a novel hexacoordinated antimony(V) dication, [(ppy)₃ Sb]²⁺.
• To elucidate the bonding geometry, stability, and dynamic behavior of this dication.
• To investigate the feasibility of generating such dications via single-electron-transfer.

Main Methods:

• Oxidative addition of chlorine to a neutral stibine precursor.
• Isolation and characterization of the hexachloroantimonate salt using X-ray crystallography.
• Spectroscopic analysis including ¹H and ¹³C NMR, and variable-temperature ¹H NMR.
• Theoretical calculations to explore geometric preferences.

Main Results:

• Successful synthesis and isolation of the air-stable hexacoordinated antimony(V) dication, [1][SbCl₆ ]₂.
• X-ray crystallography revealed a meridional octahedral bonding geometry around the antimony center.
• NMR studies indicated magnetic inequivalence of the ppy ligands and provided insights into their dynamics.
• Theoretical calculations supported the preferential formation of the meridional isomer.

Conclusions:

• The dication [1]²⁺ represents the first structurally determined [12-Sb-6]²⁺ species.
• The study demonstrates the stability and unique structural features of hexacoordinated antimony(V) dications.
• Intramolecular donor-acceptor interactions play a key role in stabilizing the dication.