EXPANDED CLOSE-PACKED FULLERIDES - THE REACTIVITY OF NA2C60 WITH AMMONIA

A novel expanded fulleride results from the room temperature reaction of Na2C60 with ammonia. The rhombohedral packing of (ND3)(8)Na2C60 ari ses from cooperative rearrangement of the face-centered cubic structur e of the starting material, via a bcc intermediate. The interfulleride distance within the formerly close-packed layers increases to 12.22 A ngstrom while 10.24 Angstrom contacts are maintained between the layer s, which retain an ABC stacking sequence. A combination of minimized C ...D repulsions and attractive N-D...pi interactions between the dynam ically reorientating Na(ND3)(4)(+) and C-60(2-) units control the stru cture.