Coordination Chemistry of a Pyrazoline Derived from 2,4-Pentanedione bis(4-Methylthiosemicarbazone). Crystal Structure of the Pyrazoline and Evidence for Metal-Mediated Ring Opening

Abstract

The heterocyclic structure of the pyrazoline obtained from reaction of 2,4-pentanedione with 4-methyl-3-thiosemicarbazide has been confirmed by X-ray crystallography. Reactions of the pyrazoline with CuII and ZnII have been probed by EPR and NMR spectroscopies respectively. The results suggest that the pyrazoline undergoes ring-opening back to the bis-thiosemicarbazone upon coordination to the transition metal, accompanied by oxidation of the central methylene group when the reactions are carried out under air.