Anion influence on co-ordination polymers of Ag(I) with 1,4-dithiacyclohexane

Abstract

The reaction of Ag(I) salts with 1,4-dithiane has produced several interesting co-ordination polymers, the structures of which vary significantly with anion. Compounds with metal ∶ ligand ratios of 2 ∶ 3, 1 ∶ 1 and 2 ∶ 1 have been produced and are discussed in the context of the influence of the anion on structural order. The recurrent topological feature of the three 2 ∶ 3 adducts, [{[Ag₂(μ₂-1,4-dithiane)₃][BF₄]₂}_∞, {[Ag₂(μ₂-1,4-dithiane)₃][CF₃SO₃]₂}_∞ and {[Ag₂(μ₂-1,4-dithiane)₃][NO₃]₂}_∞], is a {[Ag₂(μ₂-1,4-dithiane)₃]²⁺}_∞ honeycomb sheet of (6,3) topology. The principal differences between these sheets lie in the size and symmetry of the constituent hexagonal units, the packing of the sheets being governed by the anion. For the polymers with [BF₄⁻] and [CF₃SO₃⁻] anions, parallel sheets align such that the anions, which complete the four-fold co-ordination of the Ag(I) centres, are located in the hexagonal cavities of adjacent sheets; for the polymers with [NO₃⁻] anions, however, the sheets are perpendicularly interpenetrated. The structures of the three 1 ∶ 1 adducts, {[Ag(μ₂-1,4-dithiane)][BF₄]}_∞, {[Ag(μ₂-1,4-dithiane)][SCN]}_∞ and {[Ag(μ₂-1,4-dithiane)][NO₂]}_∞, are all based on the same building block, a {[Ag(μ₂-1,4-dithiane)]⁺}_∞ chain of alternating metal and organic fragments. They differ, however, in the construction of their extended networks, which are anion dependent. All three anions bridge four-co-ordinate Ag(I) centres to form {[Ag(μ-X)]⁻}_∞ chains which criss-cross the {[Ag(μ₂-1,4-dithiane)]⁺}_∞ chains. In the cases where [BF₄⁻] and [SCN⁻] anions are used, the interlinked chains generate 2-D sheets with (4,4) topology which space fill either by perpendicular two-fold interpenetration to give a 3-D CdSO₄ net (for the [BF₄⁻] complex) or by parallel stacking (for the [SCN⁻] complex). In contrast, when [NO₂⁻] acts as the anion, the interlinked chains give a 3-D diamondoid network. The 2 ∶ 1 polymer, {[Ag₂(μ₄-1,4-dithiane)][SO₄]·H₂O}_∞, has an unprecedented 3-D architecture in which inorganic pillars brace metal–organic sheets. The metal–organic sheets comprise Ag(I) centres linked by μ₂-S, μ₂-S′ bridging 1,4-dithiane ligands and the inorganic pillars comprise Ag(I) centres connected by μ₁-O (μ₁-O is used in this instance to describe an oxygen atom bound to only one silver atom), μ₁-O′, μ₂-O″-bridging sulfate anions and μ₂-O-bridging H₂O molecules.