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-Et(2)C(6)H(3)), Mes (2,4,6-Me(3)C(6)H(2)), Xyl (2,6-Me(2)C(6)H(3))) 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. (13)C{(1)H} 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}(+)···C(60)(6–) 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.