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

Abstract

The influence of terminal ligands on the structure and nuclearity of copper(II)-pyrazolates has been investigated. Exchange of the chloride ligands of [Cu 3(μ 3-X)(μ-pz) 3Cl 3] n− (X=O, OH; n=2, 1) or [Cu 3(μ 3-Cl) 2(μ-pz) 3Cl 3] 2− complexes for cyanate, acetate or bromide ligands maintains the integrity of the triangular species: PPN[Cu 3(μ 3-OH)(μ-pz) 3(NCO) 3], PPN[Cu 3(μ 3-OH)(μ-pz) 3(O 2CCH 3) 3(H 2O)] · H 2O, Bu 4N[Cu 3(μ 3-OH)(μ-pz) 3(O 2CCH 3) 3] · 3H 2O and (Bu 4N) 2[Cu 3(μ 3-Br) 2(μ-pz) 3Br 3] have been prepared and characterized by spectroscopic and X-ray diffraction techniques, respectively. In contrast, tetranuclear complexes (Bu 4N) 2[Cu 4(μ 3-OH) 2(μ-4-X-pz) 2(μ-O 2CPh) 2(O 2CPh) 4] (X=H, Cl, Br, NO 2) and the hexanuclear complex (Bu 4N) 2[Cu 6(μ 3-O)(μ 3-OH)(μ-4-NO 2-pz) 6(μ-O 2CPh) 3(O 2CPh) 2(H 2O)] · (CH 2Cl 2) 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, (Bu 4N) 2[Cu 4(μ-OH) 2(μ-pz) 4Cl 4], 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).