Vapor-Phase Growth and Structural Characterization of Single Crystals of Magnesium Doped Two-Dimensional Fullerene Polymer Mg₂C₆₀

Single crystals of magnesium doped fullerene polymer Mg2C60 can be directly grown via a binary vapor-phase mixture of Mg and C60, in sealed glass tubes at elevated temperatures. This is the first single crystal, in metal-doped two-dimensional fullerene polymers, which enables precise X-ray structural refinement. The Mg2C60 crystallizes in a monoclinic space group, I2/m, with lattice parameters of a = 9.324(2) Å, b = 9.041(2) Å, c = 14.817(3) Å, and β = 91.699(10)°. A Mg atom is located at each tetrahedral fullerene ball interstice, where the shortest Mg–C distance is 2.341(2) Å, suggesting that the Mg cation is in van der Waals contact with carbon p orbitals. The precise structure of the two-dimensional fullerene polymer network is characterized by comparison with structural data reported previously on powder samples.