A stable phosphanyl phosphaketene and its reactivity

Area of Science:

• Organophosphorus chemistry
• Main group chemistry
• Reaction mechanism studies

Background:

• Sodium phosphaethynolate (Na(OCP)) is a reactive species.
• Diazaphospholes are heterocyclic compounds containing phosphorus and nitrogen.

Purpose of the Study:

• To investigate the reaction between sodium phosphaethynolate and a bulky P-chloro-diazaphosphole.
• To characterize the resulting phosphanyl phosphaketene and its subsequent reactions.
• To elucidate the reaction mechanisms using computational methods.

Main Methods:

• Synthesis and characterization of phosphanyl phosphaketene.
• X-ray diffraction studies of the dimerized product.
• Diels-Alder trapping of a heterocyclic diphosphene intermediate.
• Density Functional Theory (DFT) computations.

Main Results:

• A stable phosphanyl phosphaketene was synthesized, exhibiting a long P-P bond (2.44 Å) indicative of a tight ion pair.
• In solution, the phosphaketene dimerized with CO loss to form 1,2,3-triphosphabicyclobutane.
• A five-membered heterocyclic diphosphene intermediate was successfully trapped.
• DFT calculations provided insights into hetero-Cope rearrangement and dimerization mechanisms.

Conclusions:

• The reaction yields a unique phosphanyl phosphaketene with unusual bonding.
• The dimerization pathway and intermediate formation are mechanistically understood.
• This study expands the known reactivity of phosphaalkynes and heterocyclic phosphorus compounds.