Cyclic alkyl amino carbenes

Cyclic(alkyl)(amino) carbenes (CAACs) are a class of stable singlet carbene ligands that feature one amino and one sp³ alkyl group adjacent to the carbene carbon atom. CAACs are a subset of N-heterocyclic carbenes (NHCs) in which the replacement of an amino group on the "classical" diaminocarbene with a saturated carbon atom results in a carbene ligand that is both a better σ-donor and π-acceptor than classical NHCs. The lone pair on the nitrogen atoms in classical NHCs allows for π-donation from both nitrogen atoms, while substitution of one nitrogen with a carbon atom results in weaker π-donation from only one nitrogen substituent, thus making CAACs stronger π-acceptors and more electrophilic than classical NHCs. Like NHCs, CAACs have tunable steric and electronic properties that make them versatile ligands in both transition metal and main group. CAACs have been heavily studied. CAACs form stable adducts with otherwise reactive or unstable molecules. In materials science, CAACs stabilize species that have promising photophysical properties for organic light emitting diodes (OLEDs) and have been shown to stabilize single molecule magnets (SMMs).