Metathesis Reactions of a NHC-Stabilized Phosphaborene.

The BP unsaturated unit is a very attractive functional group as it provides novel reactivity and unique physical properties. Nonetheless, applications remain limited so far due to the bulky nature of B/P-protecting groups, required to prevent oligomerization. Herein, we report the synthesis and isolation of a N-heterocyclic carbene (NHC)-stabilized phosphaborene, bearing a trimethylsilyl (TMS) functionality at the P-terminal, as a room-temperature-stable crystalline solid accessible via facile NHC-induced trimethylsilyl chloride (TMSCl) elimination from its phosphinoborane precursor. This phosphaborene compound, bearing a genuine B=P bond, exhibits a remarkable ability for undergoing P-centre metathesis reactions, which allows the isolation of a series of unprecedented phosphaborenes. X-ray crystallographic analysis, UV/Vis spectroscopy, and DFT calculations provide insights into the B=P bonding situation.