Effect of copper-substitution on the structure and nuclearity of Cu(II)-pyrazolates: from trinuclear to tetra-, hexa- and polynuclear complexes

The influence of terminal ligands on the structure and nuclearity of copper(II)-pyrazolates has been investigated. Exchange of the chloride ligands of [Cu3(μ3-X)(μ-pz)3Cl3]n− (X=O, OH; n=2, 1) or [Cu3(μ3-Cl)2(μ-pz)3Cl3]2− complexes for cyanate, acetate or bromide ligands maintains the integrity of the triangular species: PPN[Cu3(μ3-OH)(μ-pz)3(NCO)3], PPN[Cu3(μ3-OH)(μ-pz)3(O2CCH3)3(H2O)] · H2O, Bu4N[Cu3(μ3-OH)(μ-pz)3(O2CCH3)3] · 3H2O and (Bu4N)2[Cu3(μ3-Br)2(μ-pz)3Br3] have been prepared and characterized by spectroscopic and X-ray diffraction techniques, respectively. In contrast, tetranuclear complexes (Bu4N)2[Cu4(μ3-OH)2(μ-4-X-pz)2(μ-O2CPh)2(O2CPh)4] (X=H, Cl, Br, NO2) and the hexanuclear complex (Bu4N)2[Cu6(μ3-O)(μ3-OH)(μ-4-NO2-pz)6(μ-O2CPh)3(O2CPh)2(H2O)] · (CH2Cl2)0.5 have been obtained on substitution for benzoate ligands. An attempt to partially substitute the chlorides for tert-butoxide ligands, also provided a tetranuclear complex, (Bu4N)2[Cu4(μ-OH)2(μ-pz)4Cl4], without incorporation of the incoming ligand. Similarly, removal of all chloride ions in the absence of an appropriate substituting ligand leads to higher nuclearity metallacycles [Cu(μ-OH)(μ-pz)]n (n=6, 8, 9, 12, 14).