Phosphinophosphoranes: Mixed-Valent Phosphorus Compounds with Ambiphilic Properties

Area of Science:

• Organophosphorus Chemistry
• Synthetic Inorganic Chemistry
• Materials Science

Background:

• Phosphorus chemistry offers diverse bonding arrangements and electronic properties.
• Mixed-valent phosphorus compounds are underexplored but possess unique reactivity.
• Understanding Lewis acidity and basicity in phosphorus centers is crucial for catalysis and materials.

Purpose of the Study:

• To develop a facile synthetic route for mixed-valent phosphinophosphoranes.
• To investigate the coordination chemistry and Lewis properties of these novel compounds.
• To explore their reactivity with electrophilic reagents and Lewis acids.

Main Methods:

• Synthesis of phosphinophosphoranes via reactions of lithium phosphides/phosphanylmethanides with catecholate-based phosphorus chlorides.
• Characterization using heteronuclear nuclear magnetic resonance (NMR) spectroscopy and single-crystal X-ray diffraction.
• Evaluation of Lewis properties through reactions with borane (H₃B·SMe₂) and phenyl isothiocyanate (PhNCS).
• Computational analysis using density functional theory (DFT) to compare electronic properties.

Main Results:

• Successful synthesis of mixed-valent phosphinophosphoranes with P-P and P-CH₂-P linkages.
• Quantitative formation of phosphinophosphorane-borane adducts, confirming accessible lone-pair electrons.
• Differential reactivity with phenyl isothiocyanate, yielding phosphinophosphorylation or zwitterionic adducts.
• Structural elucidation and electronic property comparison via X-ray diffraction and DFT calculations.

Conclusions:

• A versatile synthetic strategy for mixed-valent phosphinophosphoranes has been established.
• These compounds exhibit tunable Lewis basicity and nucleophilicity.
• The study provides fundamental insights into the structure-reactivity relationships of novel phosphorus compounds.