Mechanochemical Dissociation of Singlet Carbene–CS2 Adducts

Abstract

Owing to the extensive application of singlet carbenes, their generation through the release of small molecules from stable adducts is attracting increasing research interest. This study explores the mechanochemical release of CS₂ from Carbene–CS₂ adducts formed by three distinct singlet carbenes: cyclic (alkyl)(amino)carbene (CAAC); N‐heterocyclic carbene (NHC); and N,N’‐diamidocarbene (DAC). Under ball‐milling conditions, these adducts exhibit notably different reactivities; DAC–CS₂ releases CS₂ completely within 20 min, NHC–CS₂ has a slower release rate, while CAAC–CS₂ decomposes into a complex mixture. DFT calculations reveal that the release of CS₂ from CAAC–CS₂ requires the highest activation energy (32 kcal/mol), suggesting that it is inaccessible under the reaction conditions. This is likely because of the higher HOMO energy of CAAC, which correlates with a stronger bond with CS₂, thereby limiting its dissociation. This study highlights how the electronic structures of carbenes influence their interactions with small molecules, paving the way for controlling the reactivity of carbene–small‐molecule adducts.