Correction of the space group of [Ni(bipy)₂(ONO₂)₂]·2(pyrene)

The crystal structure of [Ni(bipy)₂(ONO₂)₂]·2(pyrene), poly[[[bis(nitrato-O)nickel(II)]bis(μ-4,4′-bipyridyl-N,N′] bis(pyrene)], was originally reported in space group Pn [Biradha et al. (1999). Chem. Commun. pp. 1327–1328]. Reasons are given for changing the space group to P2₁/n. Consequently, incorrect descriptions of the title compound in the literature must be altered. In particular, the structure is not polar. It is further contended that description in terms of `complementary, interpenetrating covalent and noncovalent two-dimensional networks' is misleading as the `noncovalent network' (of pyrenes) has geometrical but not physical significance. The title compound is a typical host–guest inclusion complex.