A review of high coordination compounds of dioxouranium(VI) derived from Schiff bases of 4- aminoantipyrine

Uranium(VI) is very prominent in its complexation tendency, especially when it forms compounds exhibiting high coordination numbers. A metal acquires a high coordination number when (a) it is a small and highly charged ion with suitable vacant orbital of right energy, (b) it can attain a noble gas structure (effective atomic rule), and (c) it can attaina symmetrical shape and high CFSE in complex. U(VI) ion has positive charge which is one of the essential conditionsfor high coordination, as it will not allow the negative charge donated by electrons from the ligands to accumulate on the central metal ion. U6+ successfully reveals high coordination numbers 6 to 10. The examples of different coordination numbers of UO2 2+ coordination compounds are available in literature, many of which have been reported from our laboratory. We have synthesized and reported a number of high coordinated complexes of UO2 2+ with Schiff bases. All the coordination compounds reported herein have been suitably characterized by various physico-chemical techniques. The present review summarizes mostly our work on the UO2 2+ complexes of Schiff bases 4-aminoantipyrine, including 4-aminoantipyrine derived semicarbazones, thiosemicarbazones and some mixed ligand complexes.