A novel mechanochemical synthesis of cyclopentadienyl-type Ni/NHC complexes

A user-friendly and highly efficient mechanochemical synthesis of Ni/NHC complexes of the general formula (NHC)Ni(Cp)Cl (NHC is an N-heterocyclic carbene ligand; Cp is the cyclopentadienyl anion) under aerobic conditions is reported. The reaction between nickelocene and azolium salts (NHC proligands) proceeds with good to excellent yields of (NHC)Ni(Cp)Cl in the presence of a K₂CO₃ additive, which reduces the clumping of the reaction mixture. The developed process can be scaled up on a planetary ball mill.