Four copper(ii) pyrazolido complexes derived from reactions of 3{5}-substituted pyrazoles with CuF2 or Cu(OH)2

Abstract

Treatment of CuF₂ with 2 equiv of 3{5}-[pyrid-2-yl]pyrazole (Hpz^Py), 3{5}-phenylpyrazole (Hpz^Ph) or 3{5}-[4-fluorophenyl]pyrazole (Hpz^PhF) in MeOH, followed by evaporation to dryness and recrystallisation of the solid residues, allows solvated crystals of [{Cu(µ-pz^Py)(pz^Py)}₂] (1), [{Cu(µ-pz^Ph)₂}₄] (2) and [Cu₄F₂(µ₄-F)(µ-pz^PhF)₅(Hpz^PhF)₄] (3) to be isolated in moderate-to-good yields. Similar reactions of these three pyrazoles with Cu(OH)₂ in refluxing MeOH respectively afford 1, 2 and [Cu(pz^PhF)₂(Hpz^PhF)₂] (4) in ca. 10% yield. Crystalline 1·1/2H₂O·2CHCl₃ contains two independent dinuclear molecules with a puckered di-(1,2-pyrazolido) bridge motif, linked by a bridging, hydrogen-bonding water molecule. Compound 2·1/2C₅H₁₂, containing cyclic, square tetranuclear complex molecules, is the first homoleptic divalent metal pyrazolide to have a discrete molecular rather than polymeric structure, for a metal other than Pd or Pt. The two independent complex molecules in 3·3/4CH₂Cl₂·Hpz^PhF contain a unique tetrahedral [Cu₄(µ₄-F)]⁷⁺ core, three of whose edges are spanned by bridging pyrazolido groups. Magnetic data show that the copper centres in 1 and 3 are antiferromagnetically coupled, but that dried bulk samples of 2 do not retain their molecular structure.