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)

[Tl(Ph₂pz)] (Ph₂pz = 3,5-diphenylpyrazolate) crystallises in two forms. The first from benzene has trinuclear molecules [Tl₃₃(Ph₂pz)₃] 1 linked by intermolecular Tl-jr-t|6-Ph contacts. Within 1 the three thallium atoms are different, having coordination numbers of two (but also with theTl... η)6-Ph contact), three and four, whilst u-tin1, μ_s-η²:η¹)2:1 and (the new) μ_s-η²:η¹ modes of Ph2pz coordination are observed. Crystallisation of [TI(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 μ_s-η²:η¹ and μ_s-η²:η¹-pyrazolate coordination. In addition there is an intermolecular Tl-μ_s-η²:η¹-Ph interaction linking the tetranuclear molecules into a polymer, and sundry intramolecular Tl ⋯C contacts, the most important of which is an unsymmetrical Tl-μ_s-η²:η¹-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 μ_s-η²:η¹-Ph₂pz contact. Complex 3 features three and four coordinate Tl atoms and μ_s-η²:η¹ and μ_s-η²:η¹-pyrazolate binding, whilst 4 has three, four and five coordinate thallium atoms and solely μ_s-η²:η¹-pyrazolate ligands.