Bridging mode flexibility of 1,3-dithiacyclohexane in silver(i) co-ordination polymers

Abstract

Co-ordination polymers with Ag∶1,3-dithiane molar ratios of 1∶1, {[Ag₂(1,3-dithiane)₂][X][Y]}_∞ (X = Y = NO₃, 1; X = Y = PF₆, 2; X = Y = BF₄, 3; X = BF₄, Y = Cl, 4; X = Y = NO₂, 5, and 2∶1, {[Ag₂(1,3-dithiane)(SO₄)(H₂O)₂]·H₂O}_∞6, the extended structures of which are 1-D chains and 2-D sheets, respectively, have been synthesised and structurally characterised. The recurrent structural motif is the [Ag₂(μ-1,3-dithiane)₂]²⁺ cationic dimer in which two chair-conformation 1,3-dithiane molecules act as two-connecting units to bridge two Ag(I) centres. In 1, 2, and 6, the dimers are linked into near-linear chains by pairs of bridging anions via formation of an Ag₂X₂ rhomboid dimer. In 3, instead of forming the Ag₂X₂ (X = F) rhomboid dimer, two [BF₄⁻] anions form μ₂-F,F′-bridges which support weak Ag–S interactions between cations to give a saw-tooth chain structure. This extra Ag–S contact makes the 1,3-dithiane a three-connecting unit. In 4 and 5, the Ag(I) centres of the cationic dimer are bridged not only by two 1,3-dithiane molecules but also by a Cl⁻ or NO₂⁻ anion, respectively, to give [Ag₂(μ-1,3-dithiane)₂(μ₂-Cl)]⁺ (4) and [Ag₂(μ-1,3-dithiane)₂(μ₂-O,O′-NO₂)]⁺ (5). In 4, the Cl⁻ anion acts as a μ₄-bridge to link three [Ag₂(μ-1,3-dithiane)₂]²⁺ moieties and generate a zig-zag chain. In 5, one oxygen of the bridging NO₂⁻ anions acts as a μ₂-bridge to link two [Ag₂(μ-1,3-dithiane)₂]²⁺ dimers and generate a saw-tooth chain. Although the chains in 1, 2, 3 and 5 are uncharged, that in 4 is cationic and that in 6 is anionic. Charge balance in 4 is maintained by a non-co-ordinated [BF₄⁻] anion; that in 5 is maintained by ‘Ag(H₂O)₂⁺’, the co-ordination polyhedron of which is completed by sulfur donors from separate 1,3-dithiane molecules, which thus act as four-connecting units, and by two oxygens of separate SO₄²⁻ anions to give a two-dimensional sheet structure.