Figure 1 Part of the structure of the title compound, showing the atom-numbering scheme and with displacement ellipsoids drawn at the 35% probability level. All H atoms have been omitted for clarity. Symmetry codes: (i) -x, y, -z + [{3\over 2}]; (ii) -x + 1, y, -z + [{3\over 2}]; (iii) x - 1, y, z; (iv) x + 1, y, z.  [article HTML]