Amino Imidazolin-2-imine Ligands in Magnesium Complexes: Approaches Towards Low-Valent Mg(I) Species

Amino imidazoline-2-imines (AmIm) are a new class of chelating, monoanionic N,N´-donor ligands stronger than the analogous β-diketiminate ligands and give rise to five-membered metallacycles. The coordination chemistry of the monoanionic ligands 1,2-NHC=N−C6H4−NDipp− (i), cis-1,2-NHC=N−CMe=CMe−NDipp− (ii) was towards magnesium was investigated with the focus on the stabilization of low-valent magnesium(I) species, NHC = cyclo-C(NiPr2CMe)2, Dipp = 2,6-iPrC6H3. Both ligand systems (i) and (ii) form heteroleptic magnesium iodide species with were subjected to reduction. The complex [Mg(1,2-NHC=N−C6H4−NDipp)]2 was found to be insoluble, which prevented further purification. In contrast, the yield of the analogous complex [Mg(cis-1,2-NHC=N−CMe=CMe−NDipp)]2 was very low. As a significant side product the homoleptic complex [Mg(cis-1,2-NHC=N−CMe=CMe−NDipp)2] was identified.