Mechanistic insights of anionic ligand exchange and fullerene reduction with magnesium(i) compounds

Abstract

Ligand exchange reactions between combinations of the complexes [{(^Arnacnac)Mg}₂], where Ar = 2,6-iPr₂C₆H₃ (Dip), 2,6-Et₂C₆H₃ (Dep), 2,4,6-Me₄C₆H₂ (Mes), and 2,6-Me₂C₆H₃ (Xyl), [({Ph₂P(NDip)₂}Mg)₂], [(^Arnacnac)Li], where Ar = Mes or Xyl, and [{Ph₂P(NDip)₂}Li] were studied in deuterated aromatic and aliphatic solvents, and tetrahydrofuran. The reactions afforded product mixtures with asymmetrically substituted dimagnesium(I) complexes [(^Arnacnac)MgMg(^Ar′nacnac)], where Ar, Ar′ = Dip, Dep, Mes, Xyl and [{Ph₂P(NDip)₂}MgMg(^Arnacnac)], where Ar = Mes or Xyl, and suggest that the exchange of anionic ligands on the Mg₂²⁺ ion proceeds via an associative mechanism and is strongly dependent on ligand sterics and ligand shape, and can be very rapid. The activation reaction of fullerene C₆₀ by dimagnesium(I) complexes [{(^Arnacnac)Mg}₂] and [({Ph₂P(NDip)₂}Mg)₂] to fulleride complexes is similarly dependent on ligand sterics and ligand shape, but likely does not involve direct coordination of the fullerene to the Mg centre in dimagnesium(I) compounds prior to its reduction. The new C₆₀⁶⁻ fulleride complex [({Ph₂P(NDip)₂}Mg)₆C₆₀] was prepared, and spectroscopically and structurally characterised.