coated by graphitic carbon, in addition to multiwalled carbon nanotubes, are formed after reaction of Mo(CO)₆ with Mg at 900 °C. The edges of these cubes are 500-600 nm in length and in some cases the MgO inside the cube can be dissolved to leave carbon cubes as the sole product. (A. Gedanken et al., August 16, Adv. Mater. 2002, 14, 1167-1172)