PUB - Publikationen an der Universität Bielefeld

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)MgI2 (4) [IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene], respectively. By employing a similar strategy, the first magnesium compound (aIPr(Ph))MgI2(OEt2) (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 pK(a) value of the C4-H than that of the C2-H hydrogen atom. Salt metathesis reaction of 6 with KN(SiMe3)(2) cleanly leads to the formation of a magnesium amide derivative (aIPr(Ph))Mg{N(SiMe3)(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.