Figure 1 View of a part of the title structure. Ellipsoids are shown at the 50% probability level. [Symmetry code: (i) -0.5 + x, 0.5 - y, -0.5 + z; (ii) 1.5 - x, 0.5 + y, 1.5 - z; (iv) 1 - x, -y, 2 - z; (x) x, 1 + y, z; (xiii) 1 - x, 1 - y, 2 - z;]  [article HTML]