Hydrocarbon-soluble, hexaanionic fulleride complexes of magnesium

The reaction of the magnesium(i) complexes [{((Ar)nacnac)Mg}(2)], ((Ar)nacnac = HC(MeCNAr)(2), Ar = Dip (2,6-iPr(2)C(6)H(3)), Dep (2,6-Et2C6H3), Mes (2,4,6-Me3C6H2), Xyl (2,6-Me2C6H3)) with fullerene C-60 afforded a series of hydrocarbon-soluble fulleride complexes [{((Ar)nacnac)Mg}(n)C-60], predominantly with n = 6, 4 and 2. C-13{H-1} NMR spectroscopic studies show both similarities (n = 6) and differences (n = 4, 2) to previously characterised examples of fulleride complexes and materials with electropositive metal ions. The molecular structures of [{((Ar)nacnac)Mg}(n)C-60] with n = 6, 4 and 2 can be described as inverse coordination complexes of n [((Ar)nacnac)Mg](+) ions with C-60(n-) anions showing predominantly ionic metal-ligand interactions, and include the first well-defined and soluble complexes of the C-60(6-) ion. Experimental studies show the flexible ionic nature of the {((Ar)nacnac)Mg}+MIDLINE HORIZONTAL ELLIPSISC606- coordination bonds. DFT calculations on the model complex [{((Me)nacnac)Mg}(6)C-60] ((Me)nacnac = HC(MeCNMe)(2)) support the formulation as an ionic complex with a central C-60(6-) anion and comparable frontier orbitals to C-60(6-) with a small HOMO-LUMO gap. The reduction of C-60 to its hexaanion gives an indication about the reducing strength of dimagnesium(i) complexes.