The crystal structure of the superconducting (ND3)xNaA2C60 (0.7 ≤ × ≤ 1, A= K, Rb) fullerides (Tc= 6-15 K) has been studied by synchrotron X-ray and neutron powder diffraction. It is face-centered cubic (fcc) to low temperatures with Na+-ND3 pairs residing in the octahedral interstices. These are disordered over the corners of two "interpenetrating" cubes with the Na+ ions and the N atoms displaced by ∼2.0 Å and ∼0.5 Å from the center of the site and statically disordered over the corners of the inner and outer cube, respectively. Close contacts between the D atoms of the ND3 molecules and electron rich 6:6 C-C bonds of neighboring C60 units provide the signature of weak N-D⋯π hydrogen-bonding interactions, which control the intermolecular packing in the crystal and may determine the unusual superconducting properties.
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