Exploring Singlet Carbyne Anions and Related Low-Valent Carbon Species Utilizing a Cyclic Phosphino Substituent

The advancement of synthetic methodologies is fundamentally driven by a deeper understanding of the structure–reactivity relationships of reactive key intermediates. Carbyne anions are compounds featuring a monovalent anionic carbon possessing four nonbonding valence electrons, which were historically confined to theoretical constructs or observed solely within the environment of gas-phase studies. These species possess potential for applications across diverse domains of synthetic chemistry and ancillary fields. This Account details our focused efforts to isolate singlet carbyne anions and explores our isolation of a range of related low-valent carbon species. Our achievements include the synthesis and characterization, under normal laboratory conditions, of gold-substituted free carbenes, copper carbyne anion complexes, ketenyl anions, keteniminyl anions, and a free stannyne. These have been accomplished using a bulky cyclic phosphino substituent, which effectively stabilizes these reactive species.