Packing Motifs in [M(bpy)₂X₂] Coordination Compounds (bpy = 2,2′-bipyridine; X = F, Cl, Br, I)

Packing motifs within structurally characterized cis-[M(bpy)2X2] (M = any metal, bpy = 2,20-bipyridine, X = F, Cl, Br, I) coordination compounds have been investigated using data from the Cambridge Structural Database. Compounds fall into two classes: non-solvated cis-[M(bpy)2X2] moieties and those with additional lattice molecules (solvent or other molecules). A recurring packing motif is a dimeric unit involving intermolecular face-to-face -stacking of bpy ligands and CHbpy...X contacts, although in several cases, slippage of the stacked bpy units reduces the effectiveness of the face-to-face interaction leaving the CHbpy...X contacts as the dominant crystal-packing interaction. The prevalence of the dimeric unit versus the assembly of 1D-chains in the solid state is described.