In a previous X-ray crystallographic study of crystals of Pt(bpy)(CN)_2 (bpy = 2,2'-bipyridine) the planar molecules were reported to be exactly eclipsed, stacked directly on top of one another with a spacing of 3.33 Å so as to form a linear Pt· · ·Pt· · ·Pt chain. A reinvestigation shows this structure to be incorrect. The presence of weak intermediate layer lines indicates that the repeat distance along the stacking direction is 6.66 Å rather than 3.33 Å. Successive molecules within the stack are rotated by 180° and the resulting Pt-atom chain is slightly zigzag with a Pt· · ·Pt· · ·Pt angle of 168.6 (1)°. The implications are discussed of the determination and refinement of an apparently satisfactory, although grossly wrong, structure that was based on an incorrect unit cell and an incorrect space group
