Planar bismuth triamides: a tunable platform for main group Lewis acidity and polymerization catalysis

Area of Science:

• Organometallic Chemistry
• Main Group Chemistry

Background:

• Geometric deformation in main group compounds can induce unique properties like Lewis acidity.
• Bismuth(III) compounds typically exhibit pyramidal structures, not planar ones.

Purpose of the Study:

• To report on a novel family of planar bismuth(III) complexes.
• To investigate their tunable Lewis acidity and catalytic applications.
• To explore their potential as alternatives to toxic tin catalysts.

Main Methods:

• Synthesis and characterization of planar bismuth(III) complexes with triamide ligands.
• Assessment of Lewis acidity using a modified Gutmann-Beckett method with trimethylphosphine sulfide and triethylphosphine oxide.
• Computational studies to analyze binding affinities, intrinsic bond strength, and deformation energy.
• Evaluation of catalytic activity in ring-opening polymerization of cyclic esters.

Main Results:

• Planar bismuth(III) complexes display tunable geometric Lewis acidity.
• These complexes exhibit comparable Lewis acidity to triarylboranes but can bind two bases and show reduced soft substrate discrimination.
• Catalytic studies demonstrated high molecular weights and excellent dispersity in polymerizations using low catalyst loadings.
• Complexes maintained performance under industrially relevant conditions.

Conclusions:

• Planar bismuth complexes represent a novel neutral platform for main group Lewis acidity.
• These complexes show significant potential as efficient and less toxic catalysts for polymer synthesis, particularly for medical-grade materials.