Coordination of metalloligand [NiL] (H2L = salen type N2O2 Schiff base ligand) to the f-block elements: Structural elucidation and spectrophotometric investigation

Abstract

To investigate the coordinative interaction of a bidentate metalloligand [NiL] with f-block metal ions, two di-phenoxo bridged Ni-nf (n=4 and 5) complexes [(NiL)2Ce(NO3)3] (1) and [(NiL)UO2(NO3)2] (2) have been synthesized and characterized (H2L=N,N′-bis(α-methylsalicylidene)-1,3-propanediamine, a N2O2 donor Schiff base ligand). Single crystal structural characterizations revealed that [NiL] formed 2:1 adduct with a lanthanide Ce(NO3)3 whereas with the actinyl UO2(NO3)2, 1:1 adduct was obtained. In complex 1 the central Ce(III) ion is connected to two terminal [NiL] metalloligands through μ1,1-diphenoxido bridges to form a trinuclear coordination cluster with three chelating nitrato coligands (CeO10 tetradecahedron). Whereas in complex 2 one [NiL] is chelated to the UVIO22+ ion along with two chelating nitrato coligands to form a dinuclear core (UO8 hexagonal bipyramid). Moreover, to examine the formation of these complexes in solution, we performed UV–Vis spectrophotometric titrations of [NiL] with the respective metal ions which revealed the formation of bimetallic 1:1 and 2:1 complexes for both Ce(III) and UO22+ ions. However, we got only 1:1 and 2:1 adducts for UO22+ and Ce3+ respectively on crystallization even of varying the stoichiometry of the reactants probably due to the differences in solubility of the adducts formed.