Novel pyrazolate coordination modes and unusual Tl⋯Tl or Tl-π-(phenyl) interactions in the crystal structures of [{Tl3(Ph2pz)3}n], [{Tl4(Ph2pz)4}n], [{Tl4(Ph2pz)3(OH)}2] and [{Tl4(MePhpz)3(OH)}n] (Ph2pz = 3,5-diphenylpyrazolate; MePhpz = 3-methyl-5-phenylpyrazolate)

Abstract

[Tl(Ph₂pz)] (Ph₂pz = 3,5-diphenylpyrazolate) crystallises in two forms. The first from benzene has trinuclear molecules [Tl₃(Ph₂pz)₃] 1 linked by intermolecular Tl–π-η⁶-Ph contacts. Within 1 the three thallium atoms are different, having coordination numbers of two (but also with the Tl⋯η⁶-Ph contact), three and four, whilst μ-η¹∶η¹, μ₃-η¹∶η²∶η¹ and (the new) μ₃-η¹∶η¹∶η¹ modes of Ph₂pz coordination are observed. Crystallisation of [Tl(Ph₂pz)] from 1,2-dimethoxyethane (dme) gives tetranuclear molecules [Tl₄(Ph₂pz)₄] 2 solvated by dme. Three or four coordinate Tl atoms are observed with μ₃-η¹∶η²∶η¹ and μ₃-η¹∶η¹∶η¹-pyrazolate coordination. In addition there is an intermolecular Tl–π-η³-Ph interaction linking the tetranuclear molecules into a polymer, and sundry intramolecular Tl⋯C contacts, the most important of which is an unsymmetrical Tl–π-η⁵-Ph₂pz interaction. Crystallisation of [Tl(Ph₂pz)] or [Tl(MePhpz)] (MePhpz = 3-methyl-5-phenylpyrazolate) from dichloromethane afforded the partially hydrolysed tetranuclear cages [Tl₄(Ph₂pz)₃(OH)] 3 or [Tl₄(MePhpz)₃(OH)] 4, which associate to give a dimer and a polymer respectively owing to Tl⋯Tl interactions, supported for the dimer by an intercage distant Tl–π-η⁵-Ph₂pz contact. Complex 3 features three and four coordinate Tl atoms and μ₃-η¹∶η²∶η¹ and μ₃-η¹∶η¹∶η¹-pyrazolate binding, whilst 4 has three, four and five coordinate thallium atoms and solely μ₃-η¹∶η²∶η¹-pyrazolate ligands.