The (Bipyridyl)copper(II) Acetate System: (2,2′-Bipyridyl)copper(II) Acetate Pentahydrate (Ribbons of Planar (H2O)6 Rings Fused with Planar (H2O)4 Rings) and (2,2′-Bipyridyl)copper(II) Acetate Acetonitrile Solvate

Two crystalline complexes, (2,2′-bipyridine)Cu(CH3COO)2·5H2O (3) and (2,2′-bipyridine)Cu(CH3COO)2·CH3CN (4), have been isolated and characterized by low-temperature single-crystal X-ray diffraction experiments. Crystals of phase 3 were studied previously at room temperature (296 K) under conditions leading to rapid desolvation and less distinct characterization of the waters of crystallization. With our redetermination of 3 at 100(2) K, we present a detailed description of ribbon-like structure formed by water molecules in crystals of (2,2′-bipyridine)Cu(CH3COO)2·5H2O. Acetate oxygens are linked by hydrogen-bonding to two inequivalent waters separated by 4.72 Å; the other three water molecules are trapped in polymeric ribbons of anticooperative hydrogen-bonded six-membered rings fused with cooperative hydrogen-bonded four-rings. Water oxygens of the fused ring ribbons associate only with other water oxygens, and this water structure has a local density and pair distribution function which resembles that of liquid water. Crystals of 4 are monoclinic, with acetonitrile of solvation unassociated with the complex. In both 3 and 4, bipyridine planes interleave through π-aryl stacking.