Expedient Access to Normal‐ and Abnormal‐ N‐Heterocyclic Carbene (NHC) Magnesium Compounds from Imidazolium Salts

Treatment of imidazolium salts (IPrH)Cl ( 1 ) and (IPrH)I ( 2 ) with MeMgI leads to the formation of normal N‐heterocyclic carbene (nNHC) compounds (IPr)MgCl(I) ( 3 ) and (IPr)MgI 2 ( 4 ) [IPr = 1,3‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene], respectively. By employing a similar strategy, the first magnesium compound (aIPr Ph )MgI 2 (OEt 2 ) ( 6 ) featuring an abnormal‐NHC [aIPr Ph = 1,3‐bis(2,6‐diisopropylphenyl)‐2‐phenyl‐imidazol‐4‐ylidene] is prepared by the treatment of a C2‐arylated imidazolium salt (IPrPh)I ( 5 ) with MeMgI. While the deprotonation of 1 and 2 can be accomplished at room temperature, an elevated temperature is required to deprotonate 5 with MeMgI. This is most likely due to the higher p K a value of the C4‐H than that of the C2‐H hydrogen atom. Salt metathesis reaction of 6 with KN(SiMe 3 ) 2 cleanly leads to the formation of a magnesium amide derivative (aIPr Ph )Mg{N(SiMe 3 ) 2 } 2 ( 7 ). Compounds 3 , 4 , 6 , and 7 were characterized by elemental analyses and NMR spectroscopic studies. The molecular structures of 3 , 4 , and 6 were determined by single‐crystal X‐ray diffraction analyses.