Preparation, characterization and crystal structure of a binuclear thorium(IV) complex with a pentadentate compartmental Schiff Base

The interaction of the potentially pentadentate compartmental Schiff base, (H3L), derived by condensation of 2,6-diformyl-4-chlorophenol and o- aminophenol with thorium(IV) salts has been studied and the crystal structure of the ionic complex [Mg[Th2L3]2·6H2O determined by X-ray crystallography. The compound is monoclinic, space group P21/c, with a=12.488(6), b=22.044(5), c=24.316(5) Å, and ?=104.82(3)°; Dc=1.66 g cmt-3 for Z= 2. The structure was refined to the final conventional R of 0.067 based on 5455 observed reflexions. The two independent Th atoms of the monoanionic [Th2L3]- complex are nona-coordinate and bridged by three oxygen atoms. The Mg2+ cations, which are on crystallographic centres of symmetry, are octahedrally surrounded by H2O molecules. Selected bond distances are: Th?O (bridging) 2.47 Å (mean value), Th?O 2.31 Å (mean value), Th?N 2.74 ) Å (mean value), Mg?O 2.09 Å (mean value).