Side‐chain conformations in the isomorphous polyfluorinated {4,4′‐bis[(2,2‐difluoroethoxy)methyl]‐2,2′‐bipyridine‐κ2N,N′}dichloridopalladium and ‐platinum complexes

The polyfluorinated title compounds, M Cl₂(C₁₆H₁₆F₄N₂O₂)] or 4,4′‐(HCF₂CH₂OCH₂)₂‐2,2′‐bpy]M Cl₂ M = Pd, ( 1 ), and M = Pt, ( 2 )], have –C(H_α)₂OC(H_β)₂CF₂H side chains with H‐atom donors at the α and β sites. The structures of ( 1 ) and ( 2 ) are isomorphous, with the nearly planar (bpy)M Cl₂ molecules stacked in columns. Within one column, π‐dimer pairs alternate between a π‐dimer pair reinforced with C—H…Cl hydrogen bonds (α,α) and a π‐dimer pair reinforced with C—H_β…F(—C) interactions (abbreviated as C—H_β…F—C,C—H_β…F—C). The compounds 4,4′‐(CF₃CH₂OCH₂)₂‐2,2′‐bpy]M Cl₂ M = Pd, ( 3 ), and M = Pt, ( 4 )] have been reported to be isomorphous Lu et al. (2012). J. Fluorine Chem. 137 , 54–56], yet with disorder in the fluorous regions. The molecules of ( 3 ) or ( 4 )] also form similar stacks, but with alternating π‐dimer pairs between the (α,β; α,β) and (β,β) forms. Through (C—)H…Cl hydrogen‐bond interactions, one molecule of ( 1 ) or ( 2 )] is expanded into an aggregate of two inversion‐related π‐dimer pairs, one pair in the (α,α) form and the other pair in the (C—H_β…F—C,C—H_β…F—C) form, with the plane normals making an interplanar angle of 58.24 (3)°. Due to the demands of maintaining a high coordination number around the metal‐bound Cl atoms in molecule ( 1 ) or ( 2 )], the ponytails of molecule ( 1 ) or ( 2 )] bend outward; in contrast, the ponytails of molecule ( 3 ) or ( 4 )] bend inward.