N-Heterocyclic carbenes (NHCs) are valuable ligands in transition metal catalysis, due to their unique electronic properties. However, only a few routes toward unsymmetrically substituted, saturated NHCs are known. We have successfully applied the multicomponent synthesis of 2H-2-imidazolines for the preparation of a range of diversely substituted imidazolidin-2-ylidene complexes under mild conditions. In the desired NHC precursors the substituents at N-1, N-3, C-4, and C-5 were varied easily and independently by choosing the appropriate amine, aldehyde, isocyanide, or halide as starting material. Subsequent formation of the imidazolium salts followed by deprotonation with KO t Bu and direct complexation of the in situ-generated NHCs at room temperature affords Rh-and Ir-NHC complexes. Properties of the resulting complexes were studied with 13 C NMR spectroscopy and X-ray crystallography.
Reaction of (o-phenylene)magnesium (1) with CH3MCl2 (2; M = Al, Ga, In) gave access to
the corresponding methyl(o-phenylene)metal compounds 3 ((1,2-C6H4MCH3)
n
). These novel
1,2-dimetalated benzene derivatives of group 13 were characterized by their spectral data
and, in the case of 3b (M = Ga, n = 2), by a single-crystal X-ray structure determination.
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