Crystal structures of two copper(I)-6,6-dimethyl-2,2-bipyridyl (dmbpy) compounds, [Cu(dmbpy)₂]₂[MF₆]xH₂O (M = Zr, Hf; X = 1.134, 0.671)

The syntheses and crystal structures of two bimetallic molecular compounds, namely, bis[bis(6,6-dimethyl-2,2-bipyridine)copper(I)] hexafluoridozirconate(IV) 1.134-hydrate, [Cu(dmbpy)2]2[ZrF6]1.134H2O (dmbpy = 6,6-dimethyl-2,2-bipyridyl, C12H12N2), (I), and bis[bis(6,6-dimethyl-2,2-bipyridine)copper(I)] hexafluoridohafnate(IV) 0.671-hydrate, [Cu(dmbpy)2]2[HfF6]0.671H2O, (II), are reported. Apart from a slight site occupany difference for the water molecule of crystallization, compounds (I) and (II) are isostructural, featuring isolated tetrahedral cations of copper(I) ions coordinated by two dmbpy ligands and centrosymmetric, octahedral anions of fluorinated early transition metals. The tetrahedral environments of the copper complexes are distorted owing to the steric effects of the dmbpy ligands. The extended structures are built up through Coulombic interactions between cations and anions and π-π stacking interactions between heterochiral Δ- and Λ-[Cu(dmbpy)2]+ complexes. A comparison between the title compounds and other [Cu(dmbpy)2]+ compounds with monovalent and bivalent anions reveals a significant influence of the cation-to-anion ratio on the resulting crystal packing architectures, providing insights for future crystal design of distorted tetrahedral copper compounds.