P^I and P^III Ions Supported by BZIMPY Ligands

Area of Science:

• Inorganic Chemistry
• Organophosphorus Chemistry
• Coordination Chemistry

Background:

• Phosphorus compounds exhibit diverse oxidation states and reactivity.
• Stabilizing multiple oxidation states of phosphorus within the same ligand framework presents a synthetic challenge.

Purpose of the Study:

• To synthesize and characterize novel P^III-X and P^I phosphorus compounds supported by a 2,6-bis(benzimidazole-2-yl)pyridine (BZIMPY) ligand.
• To investigate the cycling between P^III-X and P^I forms and explore their reactivity as transfer agents.

Main Methods:

• Synthesis of dicationic triflate salts of P^III-X species.
• Reductive transformations using phosphine oxides and triphenylphosphine.
• Computational studies to rationalize reaction mechanisms.
• Characterization using NMR spectroscopy, elemental analysis, and X-ray crystallography.

Main Results:

• Stable P^III-X and P^I forms of phosphorus compounds featuring the BZIMPY ligand were successfully synthesized and cycled.
• Reductive pathways were observed with different phosphorus nucleophiles, leading to P^I species.
• The P^III-X compounds demonstrated strong Lewis acidity and acted as X⁺, PX, and P⁺ transfer agents.
• The P^I compounds were effective P⁺ transfer agents.
• Re-oxidation to P^III-X was achieved using N-halosuccinimides.

Conclusions:

• A novel class of phosphorus compounds capable of facile cycling between P^III-X and P^I oxidation states was developed.
• These compounds exhibit unique reactivity as Lewis acids and versatile phosphorus transfer agents.
• The findings provide new insights into phosphorus chemistry and open avenues for designing novel phosphorus-based reagents.