Solvent induced reactivity of 3,5-dimethylpyrazole towards zinc (II) carboxylates

The reactions of 3,5-dimethylpyrazole with zinc(II) acetate dihydrate and varieties of aromatic carboxylic acids led to formation of mono-nuclear zinc complexes of composition [Zn(HDMP)(2)(RCO2)(2)] (R= C6H5, p-CH3-C6H4, p-NO2-C6H4 etc. HDMP = 3,5-dimethylpyrazole) in methanol, whereas the same reactants in dimethylformamide (DMF) gave binuclear 3,5-dimethylpyrazolato bridged zinc carboxylate complexes containing monodentate 3,5-dimethylpyraozole ligands with composition [Zn-2(mu-DMP)(2)(HDMP)(2)(RCO2)(2)]. The mononuclear complexes can be converted to the corresponding binuclear complexes by simply dissolving in DMF. The reaction of zinc(II) acetate dihydrate with p-nitrobenzoic acid and 3,5-dimethylpyrazole in different solvents gave solvated mononuclear complexes of the corresponding solvent. All these solvated complexes having the core [Zn(HDMP)(2)(p-NO2-C6H4CO2)(2)] contain two structurally independent molecules in the asymmetric unit (Z' = 2).