(N2)6Ne7: A High Pressure van der Waals Insertion Compound

The binary phase diagram of N-2-Ne mixtures has been measured at 296 K by visual observation and Raman spectroscopy. The topology of the phase diagram points to the existence of the stoichiometric compound (N-2)(6)Ne-7. Its structure has been solved by single-crystal synchrotron x-ray diffraction. The N-2 molecules form a guest lattice that hosts the Ne atoms. This insertion compound can be viewed as a clathrate with the centers of the N-2 molecules forming distorted dodecahedron cages, each enclosing 14 Ne atoms. Remarkably, the (N-2)(6)Ne-7 compound is somehow the first clathrate organized by the quadrupolar interaction.