Low-valent Mg(I) complexes by ball-milling

Abstract

Mechanochemistry has great potential in the syntheses of low-valent Mg(I) complexes. Magnesium iodide precursors with three different β-diketiminate (BDI) ligands of varying bulk have been reduced with K/KI (or Na/NaCl) using the ball-mill. Depending on the steric bulk of the ligand, the raw products are intensely colored powders, indicating the presence of (BDI)Mg⋅ radicals. Extraction with pentane gave (BDI)Mg−Mg(BDI) in excellent yields. Reaction of the powder with H2 prior to extraction gave [(BDI)MgH]2. Extraction with benzene gave (BDI)Mg(C6H6)Mg(BDI) with a dearomatized puckered benzene dianion. Ball-milling in the presence of triphenylbenzene gave a dinuclear Mg complex with a Ph3C6H3-dianion which slowly decomposed to (BDI)Mg−Mg(BDI) and Ph3C6H3.