Conversion of Bestmann Ylide into Carbophosphinocarbene

Abstract The ortho ‐carboranyl carbophosphinocarbene (CPC) has been synthesized through a click‐type reaction between the super strained carborane‐fused borirane 1,2‐BN(SiMe 3 ) 2 –1,2‐C 2 B 10 H 10 and Bestmann ylide Ph 3 PCCO. The [Cl(CO)₂Ir‐CPC] and [Cl 3 Ga‐CPC] complexes were synthesized, allowing the measurement of their Tolman electronic parameter (TEP) and the sum of Cl─Ga─Cl bond angles (∑ClGaCl), respectively. These data highlight their remarkable electron‐donating ability. Further insights into its electron‐donating properties were gained through theoretical calculations, including analysis of frontier orbitals and proton affinity (PA). Preliminary reactivity investigations demonstrate that the new CPC readily forms adducts with boranes and can effectively stabilize borenium cations. Its strong nucleophilicity enables reactions with carbon dioxide, while its exceptional Brønsted basicity allows it to deprotonate imidazolium to generate carbene species.