Cu, Ni and Zn complexes based on bipyrazole ligand: synthesis and identification by mass spectroscopy

The state of the art for the pyrazole chemistry that the pyrazole unit (or 1,2-diazole) is a simple five-membered ring system consisting of two unsaturated double bonds, three carbon atoms and two nitrogen atoms in adjacent positions. Pyrazole (term given for the first time by Ludwig Knorr in 1883) is a structural isomer of imidazole, its name comes from the pyrrole ring in which a CH group has been replaced by an atom of nitrogen. In terms of reactivity, the two sp2 hybridized nitrogen atoms have different properties: one is basic, behaving like that of pyridine (one proton acceptor) can undergo protonation in acidic medium and the other has the property of nitrogen to pyrrole its doublet participating in the aromaticity of the cycle (one proton donor). All carbon atoms can be substituted. The aromatic nature of pyrazole is due to the existence of four π-electrons and a pair of electrons located on the NH nitrogen. Electrophilic substitution reactions occur preferentially at position 4 and nucleophilic attacks at positions 3 and 5. In this short communication, we will show the preparation of five complexes (C1-C5) based on the coordination of two equivalents of bipyrazole (5,5'-diphenyl-1H,1'H-3,3'-bipyrazole) 4 as ligand and one equivalent of transition metals such as Cu(NO3)2 ; Cu(CH3COO)2, Co(NO3)2 ; NiCl2 and ZnCl2. These nitrogen complexes were characterized by mass spectroscopy analysis.