Copper complexes from 3,5-disubstituted N-hydroxyethylpyrazole ligands: Cleavage of C-N bond as well as formation of second coordination sphere complexes

Abstract

The coordination behaviour of two N,O-hybrid hydroxyethylpyrazole ligands, 2-(3,5-diphenyl-1H-pyrazol-1-yl)ethanol, HL1; and (2-(3,5-di(2-pyridyl)-1H-pyrazol-1-yl)ethanol, HL2; with CuCl2·2H2O and Cu(NO3)2·3H2O were studied. Four copper complexes: [CuCl(µ-L1)]2·HL1 (1), [CuCl2(HL2)]·H2O (2A), [Cu(NO3)(3,5-hdppz)(µ-L1)]2·2CH3CN (3), (3,5-hdppz = 3,5-diphenylpyrazole) and [Cu(H2O)(3,5-dpypz)]2(NO3)2·H2O (4), (3,5-dpypz = 3,5-(2-pyridyl)pyrazolate) were isolated and characterized by analytical methods and spectroscopical studies. From their crystal structure, a Npz-C bond cleavage was observed for HL1 and HL2 upon reaction with Cu(NO3)2·3H2O, yielding the unexpected complexes 3 and 4, respectively. Overall, these complexes provided great structural diversity, as dimers (asymmetric and symmetric), monomers and ionic complexes were obtained. Finally, magnetic susceptibility measurements for 3 were carried out, showing the dependence of the magnetic moment on Cu-O-Cu angles.