N‐Heterocyclic Carbene–Phosphinidene Adducts: Synthesis, Properties, and Applications

Syntheses, properties, and reactivity of N‐heterocyclic carbene–phosphinidene adducts are reviewed. These adducts, formally built by combining a phosphinidene with a carbene, are characterized by high nucleophilicity at the phosphorus atom. The main types of reactivity these adducts exhibit are: Lewis‐base reactivity towards main group and organic compounds as well as transition‐metal complexes, substitution reactions at the phosphorus atom with main group compounds and transition‐metal complexes, and phosphinidene transfer reactions resulting in C–P bond cleavage. These differ substantially from the classic phosphaalkenes. N‐heterocyclic carbene–phosphinidene adducts are cyclic C‐amino substituted phosphaalkenes, which feature high nucleophilicity at the phosphorus atom. This review summarizes their syntheses, properties, and reactivity.