Constrained Phosphine Chalcogenide Selenoethers Supported by peri-Substitution

Area of Science:

• Organometallic Chemistry
• Solid-State Chemistry
• Computational Chemistry

Background:

• Peri-substituted acenaphthenes offer a unique scaffold for exploring electronic interactions.
• Oxidation of phosphine and selenium moieties can significantly alter molecular structure and dynamics.
• Through-space coupling (J_PSe) in related systems provides a probe for lone pair interactions.

Purpose of the Study:

• To synthesize and characterize novel oxidized phosphorus and selenium peri-substituted acenaphthene derivatives.
• To investigate the fluxional behavior and rotameric preferences of these new compounds in solution and solid states.
• To understand the impact of phosphine oxidation on the through-space P-Se coupling.

Main Methods:

• Synthesis and full characterization of novel organophosphorus and organoselenium compounds.
• Single-crystal X-ray diffraction for solid-state structural determination.
• Solution and solid-state Nuclear Magnetic Resonance (NMR) spectroscopy, including Variable-Temperature NMR (VT NMR).
• Density Functional Theory (DFT) calculations to support experimental findings.

Main Results:

• Isolation and characterization of a series of P(V) and Se(II) peri-substituted acenaphthene species.
• Observation of fluxional behavior in solution attributed to two major rotamers.
• Identification of major rotamers in both solid and solution states using VT NMR, DFT, and solid-state NMR.
• Complete loss of the through-space J_PSe coupling upon oxidation of the phosphine group.

Conclusions:

• Phosphine oxidation in these peri-substituted acenaphthenes leads to significant changes in molecular dynamics.
• The sequestration of the phosphine lone pair upon oxidation is responsible for the loss of through-space J_PSe coupling.
• Combined experimental and computational methods are crucial for elucidating complex fluxional behavior and electronic interactions in organometallic systems.