Silver(i) complexes of bis- and tris-(pyrazolyl)azine derivatives – dimers, coordination polymers and a pentametallic assembly

Abstract

Silver(I) complexes of 2,4,6-tri(pyrazol-1-yl)pyridine (tpp), 2,4,6-tri(pyrazol-1-yl)pyrimidine (tpym), 2,4,6-tri(pyrazol-1-yl)-1,3,5-triazine (tpt) and 2,4-di(pyrazol-1-yl)-1,3,5-triazine (bpt) are reported. Dinuclear [Ag₂(μ-tpp)₂(MeCN)₂][BF₄]₂·2MeCN and [Ag₂(μ-tpym)₂(MeCN)₂][BF₄]₂ are formed from approximately planar [AgL(NCMe)]⁺ (L = tpp or bpym) centres, which dimerise via apical interactions to the pendant pyrazolyl donor on each ligand. Two polymeric solvatomorph phases [Ag₂(μ-tpp)₂][BF₄]₂·nMeNO₂ were obtained by crystallising AgBF₄ and tpp from nitromethane solution. One is composed of the same dimeric [Ag₂(μ-tpp)₂]²⁺ motif as the MeCN solvates, but with semibridging pyrazolyl substitutents replacing the solvent ligands. The other form has helicate [Ag₂(μ-tpp)₂]²⁺ dimers linked into chains by unsupported Ag⋯Ag interactions. In contrast, [Ag₅(μ₃-tpym)₄][BF₄]₅·2MeNO₂ contains discrete pentametallic assemblies, of a flattened [Ag₄(μ-tpym)₄]⁴⁺ molecular square centred by the fifth silver ion. Three helical or linear 1D coordination polymer topologies are described for [Ag(μ-tpt)]X (X⁻ = BF₄⁻ or ClO₄⁻), where ditopic tpt ligands bind one silver ion in a [2 + 1] geometry and the other in bidentate, [1 + 1] or monodentate fashion. Finally, [Ag(bpt)]BF₄ is a polymer of square planar silver ions linked by bis-bidentate bpt ligands. Most of the tpt and bpt structures include short anion⋯π contacts to the ligand triazinyl rings. Electrospray mass spectra confirm the oligomeric nature of the Ag/tpym and tpt complexes in MeNO₂ solution.