Subtle role of polyatomic anions in molecular construction: Structures and properties of AgX bearing 2,4′-thiobis(pyridine) (X^- = NO₃^-, BF₄^-, CIO₄^-, PF₆^-, CF₃CO₂^-, and CF₃SO₃^-)

Studies on the subtle effects and roles of polyatomic anions in the self-assembly of a series of AgX complexes with 2,4′-Py₂S (X^- = NO₃^-, BF₄^-, ClO₄^-, PF₆^-, CF₃CO₂^-, and CF₃SO₃^-; 2,4′-Py₂S = 2,4′-thiobis(pyridine)) have been carried out. The formation of products appears to be primarily associated with a suitable combination of the skewed conformers of 2,4′-Py₂S and a variety of coordination geometries of Ag(I) ions. The molecular construction via self-assembly is delicately dependent upon the nature of the anions. Coordinating anions afford the 1:1 adducts [Ag(2,4′-Py₂S)X] (X^- = NO₃^- and CF₃CO₂^-), whereas noncoordinating anions form the 3:4 adducts [Ag₃(2,4′-Py₂S)₄]X₃ (X^- = ClO₄^- and PF₆^-). Each structure seems to be constructed by competition between π-π interactions of 2,4′-Py₂S spacers vs Ag⋯X interactions. For ClO₄^- and PF₆^-, an anion-free network consisting of linear Ag(I) and trigonal Ag(I) in a 1:2 ratio has been obtained whereas, for the coordinating anions NO₃^- and CF₃CO₂^-, an anion-bridged helix sheet and an anion-bridged cyclic dimer chain, respectively, have been assembled. For a moderately coordinating anion, CF₃SO₃^-, the 3:4 adduct [Ag₃(2,4′-Py₂S)₄] (CF₃SO₃)₃ has been obtained similarly to the noncoordinating anions, but its structure is a double strand via both face-to-face (π-π) stackings and Ag⋯Ag interactions, in contrast to the noncoordinating anions. The anion exchanges of [Ag₃(2,4′-Py₂S)₄]X₃ (X^- = BF₄^-, ClO₄^-, and PF₆^-) with BF₄^-, ClO₄^-, and PF₆^- in aqueous media indicate that a [BF₄^-] analogue is isostructural with [Ag₃(2,4′-Py₂S)₄]X₃ (X^- = ClO₄^- and PF₆^-). Furthermore, the anion exchangeability for the noncoordinating anion compounds and the X-ray data for the coordinating anion compounds establish the coordinating order to be NO₃^- > CF₃CO₂^- > CF₃SO₃^- > PF₆^- > ClO₄^- > BF₄^-.