Differences Between Gas-Phase and Solid-State Molecular Structures of the Simplest Phosphonium Ylide, Me₃ P=CH₂

Area of Science:

• Organometallic Chemistry
• Computational Chemistry
• Structural Chemistry

Background:

• Trimethylphosphonium methylide (Me3P=CH2) is the simplest phosphonium ylide.
• Understanding its molecular structure is crucial for organophosphorus chemistry.
• Previous structural data may not fully represent its behavior in different phases.

Purpose of the Study:

• To determine the accurate gas-phase molecular structure of trimethylphosphonium methylide.
• To compare the gas-phase structure with its solid-state structure and theoretical predictions.
• To elucidate the bonding and electronic properties of this fundamental phosphonium ylide.

Main Methods:

• Reanalysis of existing 1977 gas-electron-diffraction data.
• High-level theoretical calculations (e.g., DFT).
• Comparison of experimental gas-phase data with solid-state structural information.

Main Results:

• The reanalyzed gas-electron-diffraction data reveals a heavy-atom core structure for Me3P=CH2.
• The determined gas-phase geometry is consistent with current theoretical calculations.
• Significant differences were observed between the gas-phase and solid-state molecular structures.

Conclusions:

• The molecular structure of trimethylphosphonium methylide differs significantly between the gas and solid phases.
• Theoretical calculations accurately predict the gas-phase geometry.
• This study clarifies the structural nuances of a fundamental phosphonium ylide, impacting organophosphorus chemistry research.