The varied structures of cobalt(II)–pyridine (py)–sulfate: [Co(SO(4))(py)(4)](n), [Co(2)(SO(4))(2)(py)(6)](n), and [Co(3)(SO(4))(3)(py)(11)](n)

The solid-state structures of two cobalt–pyridine–sulfate compounds, namely catena-poly[[tetra­kis­(pyridine-κN)cobalt(II)]-μ-sulfato-κ(2) O:O′], [Co(SO(4))(C(5)H(5)N)(4)](n), (1), and catena-poly[[tetra­kis­(pyridine-κN)cobalt(II)]-μ-sulfato-κ(3) O:O′,O′′-[bis­(pyridine-κN)cobalt(II)]-μ-sulfato-κ(3) O,O′:O′′](n), [Co(2)(SO(4))(2)(C(5)H(5)N)(6)](n), (2), are reported. Compound (1) displays a polymeric structure, with infinite chains of Co(II) cations adopting octa­hedral N(4)O(2) coordination environments that involve four pyridine ligands and two bridging sulfate ions. Compound (2) is also polymeric with infinite chains of Co(II) cations. The first Co center has an octa­hedral N(4)O(2) coordination environment that involves four pyridine ligands and two bridging sulfate ligands. The second Co center has an octa­hedral N(2)O(4) coordination environment that involves two pyridine ligands and two bridging sulfate ions that chelate the Co atom. The structure of (2) was refined as a two-component inversion twin.