Hydrocarbon-soluble, hexaanionic fulleride complexes of magnesium.

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