Acid-Driven Dimensionality Control of Cd(II) Complexes: From Discrete Double Open Cubane to One- and Three-Dimensional Networks

Reaction
of CdCl2 with hep-H [hep-H = 2-(2-hydroxyethyl)­pyridine]
in MeOH at 298 K yields the double open cubane tetramer [Cd2(μ-Cl)2­(μ3-Cl)­(hep-H)2Cl]2 (1). 1 on reaction
with methanolic HCl, HNO3, and H2SO4 transforms into a one-dimensional (1D) polymeric chain [Cd­(μ2-Cl)2(Cl)­(hep-H2)]n (2), ribbon-shaped polymeric structure
[[Cd5Cl12(H2O)3]­(hep-H2)2]n (3), and three-dimensional network [Cd­(SO4)­(H2O)]n (4) with topology seh-4,6-C2/c net, respectively. The similar reactions of CdCl2 with other pyridine alcohols such as hmp-H [hmp-H = 2-(2-hydroxymethyl)­pyridine]
and hpp-H [hpp-H = 2-(2-hydroxypropyl)­pyridine] yield 1D polymeric
chains [Cd­(μ2-Cl)2­(hmp-H)]n (5) and [Cd­(μ2-Cl)2­(hpp-H)]n (6), respectively. Similar to 1, upon treatment with methanolic
HCl 5 and 6 also transform into respective
1D polymeric chains [Cd2(μ2-Cl)4­(Cl)2(hmp-H2)2]n (7) and [Cd­(μ2-Cl)2­(Cl)­(hpp-H2)]n (8), analogous to 2. However, their
reactions with methanolic HNO3 and H2SO4 result in nonisolable products. In 1, 5, and 6, the pyridine alcohols are bonded to Cd­(II)
in bidentate fashion via their O and N atoms, whereas in 2, 7, and 8 due to protonation of pyridine
nitrogen these ligands are bonded in a monodentate fashion via the
alcoholic O atom.