Dioxouranium complexes as ligand. Synthesis and characterization of sandwich-type polyoxometalates [X2W18(UO2)2{(H2O)3M}2O68]10− (X = AsV and PV) (M = CoII, CuII, MnII, NiII and ZnII)

The title complexes are synthesized by the reaction of an unusual ligand of [K2P2W18(UO2)2O68]12− (1) and [KAs2W18(UO2)2O68]13− (2) with divalent metal ions of CoII, CuII, MnII, NiII and ZnII in 1:2 mole ratio and are characterized by elemental analysis, IR, 31P NMR, UV–Vis spectroscopy, TGA, and single crystal structure analysis. Crystals of [P2W18(UO2)2{(H2O)3Co}2O68]10− (1a) and [As2W18(UO2)2{(H2O)3Cu}2O68]10− (2b) are orthorhombic space group Cmca. Both 1a and 2b have structures in which two [M(H2O)3] (M = CoII, CuII) and two UO2 groups are sandwiched between two symmetry equivalent XW9O349- (XW9) (X = P, As) units in a virtual Ci symmetry. In solution, 1a and [P2W18(UO2)2{(H2O)3Zn}2O68]10− (1d) give two-line P NMR spectra that are consistent with a Cs symmetry structures so, are not consistent with the solid-state structures. The sodium salts of them give one-line P NMR spectra and are consistent with the Ci symmetry of solid-state structures. The uranium atoms have pentagonal-bipyramidal coordination, achieved by three equatorial bonds to the one XW9 and two bonds to the other. The M atoms have octahedral or square pyramidal coordination, but only one bond to the one XW9 and one bond to the other.

Graphical abstractThe new complexes of [X2W18(UO2)2{(H2O)3M}2O68]10− (X = PV and AsV) and (M = CoII, CuII, MnII, NiII and ZnII) were synthesized by reaction of [K2P2W18(UO2)2O68]12− and [KAs2W18(UO2)2O68]13− ligands, respectively with MII salts and characterized by elemental analysis, IR, 31P NMR, UV–Vis spectroscopy and single crystal structure analysis. The P NMR spectra show that the complexes have Cs symmetry structures in solution while, in solid state the complexes have Ci symmetry structures.Figure optionsDownload full-size imageDownload as PowerPoint slide