An equilibrium between [(SIMes)Cu-CF 3 ] ( 1, SIMes = 1,3-dimesitylimidazolin-2-ylidene) and the cuprate salt [(SIMes) 2 Cu][(CF 3 ) 2 Cu] ( 2 ) was observed. Synthetic methods to prepare and isolate 2 are reported. Trifluoromethylations using equilibrium mixtures of 1 and 2 occur readily for aryl iodides and even occur for aryl bromides at 90 °C. Kinetic data suggest the cuprate form does not play a significant role in trifluoromethylations using N -heterocyclic carbene complexes of copper.
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Dubinina et al. (2008) studied this question.