Phosphorus-Ylides: Powerful Substituents for the Stabilization of Reactive Main Group Compounds

Phosphorus ylides are 1,2-dipolar compounds with a negative charge at the carbon atom. This charge is stabilized by the neighboring onium moiety, but can also be shifted towards other substituents thus making ylides to strong π donor ligands and hence to ideal substituents to stabilize reactive compounds such as cations and low-valent main group species. Furthermore, the donor strength as well as the steric properties can easily be tuned to meet different requirements for stabilizing reactive compounds and for tailoring the properties and reactivities of the main group element. Albeit the use of ylide substituents in main group chemistry is still in its infancy, first examples of isolated compounds impressively demonstrate the potential of these ligands. This review summarizes the most important discoveries also in comparison to other substituents, thus outlining avenues for future research directions.