Phosphaarsenes - Combining Phospha- and Arsa-Wittig-Reagents.

Area of Science:

• Organometallic Chemistry
• Main Group Chemistry
• Inorganic Synthesis

Background:

• Dipnictenes (RPnPnR) are dimers of pnictinidenes (R-Pn).
• Phosphanylidene- and arsanylidenephosphoranes (R-Pn(PMe3)) serve as precursors for pnictinidene fragments.

Purpose of the Study:

• To synthesize and characterize novel arsaphosphenes (RP=AsR").
• To investigate the properties and reactivity of a specific arsaphosphene, Mes*P=As^DipTer.
• To explore the magnetic shielding effects on the phosphorus atom in arsaphosphenes.

Main Methods:

• Thermal treatment of 1:1 mixtures of R-P(PMe3) and R'-As(PMe3).
• Solid-state 31P NMR spectroscopy.
• Computational methods (e.g., DFT calculations).

Main Results:

• Successful synthesis of three arsaphosphenes, including Mes*P=As^DipTer.
• Observation of a large 31P NMR chemical shift anisotropy (ca. 920 ppm) for Mes*P=As^DipTer.
• Computational studies elucidated the pronounced magnetic deshielding of the phosphorus atom.
• Demonstration of Mes*P=As^DipTer's reactivity, splitting into NHC adducts.

Conclusions:

• Arsaphosphenes can be accessed through thermal reactions of phosphanylidene- and arsanylidenephosphoranes.
• The electronic structure of arsaphosphenes leads to significant magnetic deshielding at the phosphorus center.
• These compounds exhibit interesting reactivity patterns, such as dissociation into pnictinidene fragments.