The reaction of the magnesium(i) complexes [{(Arnacnac)Mg}2], (Arnacnac = HC(MeCNAr)2, Ar = Dip (2,6-iPr2C6H3), Dep (2,6-Et2C6H3), Mes (2,4,6-Me3C6H2), Xyl (2,6-Me2C6H3)) with fullerene C60 afforded a series of hydrocarbon-soluble fulleride complexes [{(Arnacnac)Mg} n C60], predominantly with n = 6, 4 and 2. 13C{1H} 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 [{(Arnacnac)Mg} n C60] with n = 6, 4 and 2 can be described as inverse coordination complexes of n [(Arnacnac)Mg]+ ions with C60 n- anions showing predominantly ionic metal-ligand interactions, and include the first well-defined and soluble complexes of the C60 6- ion. Experimental studies show the flexible ionic nature of the {(Arnacnac)Mg}+···C60 6- coordination bonds. DFT calculations on the model complex [{(Menacnac)Mg}6C60] (Menacnac = HC(MeCNMe)2) support the formulation as an ionic complex with a central C60 6- anion and comparable frontier orbitals to C60 6- with a small HOMO-LUMO gap. The reduction of C60 to its hexaanion gives an indication about the reducing strength of dimagnesium(i) complexes.
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