Reversing Lewis acidity from bismuth to antimony

Area of Science:

• Organometallic chemistry
• Catalysis
• Lewis acid chemistry

Background:

• Investigating neutral and cationic models of (Mesityl)2EX compounds where E = Sb, Bi and X = Cl-, OTf-.
• Exploring the electronic properties and reactivity of antimony and bismuth complexes.

Purpose of the Study:

• To demonstrate the reversal of Lewis acidity between bismuth and antimony based on structural and electronic factors.
• To showcase the superior catalytic efficiency of (Mesityl)2SbOTf compared to (Mesityl)2BiOTf in the reduction of phosphine oxides.

Main Methods:

• Synthesis and characterization of novel antimony and bismuth Lewis acids.
• Catalytic reduction of phosphine oxides using the synthesized Lewis acids.
• Computational studies to understand the mechanism and Lewis acidity trends.

Main Results:

• Reversal of Lewis acidity from bismuth to antimony was achieved by tuning the ligand environment.
• (Mesityl)2SbOTf exhibited higher efficiency in the catalytic reduction of phosphine oxides to phosphines than (Mesityl)2BiOTf.
• Experimental and computational data provide insights into the structure-activity relationships.

Conclusions:

• The study successfully demonstrates the tunable Lewis acidity of (Mesityl)2EX compounds.
• Antimony-based Lewis acids can be more effective catalysts than their bismuth counterparts for specific transformations.
• Findings will guide the rational design of novel Lewis acids for catalytic applications.