Formation of a nona-nuclear copper(II) cluster with 3,5-di-methyl-pyrazolate starting from an NHC complex of copper(I) chloride.

The complete nona-nuclear cluster in bis-[1,3-bis-(2,6-di-methyl-phen-yl)imid-azol-ium] di-μ-chlorido-tetra-chlorido-octa-kis-(μ-3,5-di-methyl-pyrazolato)hexa-μ3-hydroxido-nona-copper(II) chloro-form disolvate, [HIXy]2[Cu9(μ-pz*)8(μ3-OH)6(μ2-Cl)2Cl4]·2CHCl3 or (C19H21N2)2[Cu9(C5H7N2)8Cl6(OH)6]·2CHCl3, where pz* is the 3,5-di-methyl-pyrazolyl anion, C5H7N2 -, and HIXy is the 1,3-bis-(2,6-di-methyl-phen-yl)imidazolium cation, C19H21N2 +, is generated by a crystallographic centre of symmetry with a square-planar CuII ion bound to four μ3-OH ions lying on the inversion centre. Of the four remaining unique CuII atoms, three adopt CuN2O2Cl square-pyramidal coordination geometries with the chloride ion in the apical position and one has a distorted CuN2OCl tetra-hedral geometry. The dianionic nona-nuclear core can be described as a 24-membered [CuNN]8 ring that contains a Cu9O6Cl6 core. The cluster features three intra-molecular O-H⋯Cl hydrogen bonds. In the crystal, weak C-H⋯N and C-H⋯Cl inter-actions link the components. Polynuclear paramagnetic clusters of this type are of considerable inter-est due to their relevance to both the bioinorganic and single-mol-ecule magnets research fields.