Dioxouranium complexes as ligand. Synthesis and characterization of sandwich-type polyoxometalates [X 2W 18(UO 2) 2{(H 2O) 3M} 2O 68] 10− (X = As V and P V) (M = Co II, Cu II, Mn II, Ni II and Zn II)

Abstract

The title complexes are synthesized by the reaction of an unusual ligand of [K 2P 2W 18(UO 2) 2O 68] 12− ( 1) and [KAs 2W 18(UO 2) 2O 68] 13− ( 2) with divalent metal ions of Co II, Cu II, Mn II, Ni II and Zn II 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 [P 2W 18(UO 2) 2{(H 2O) 3Co} 2O 68] 10− ( 1a) and [As 2W 18(UO 2) 2{(H 2O) 3Cu} 2O 68] 10− ( 2b) are orthorhombic space group Cmca. Both 1a and 2b have structures in which two [M(H 2O) 3] (M = Co II, Cu II) and two UO 2 groups are sandwiched between two symmetry equivalent XW 9 O 34 9 - (XW 9) (X = P, As) units in a virtual C i symmetry. In solution, 1a and [P 2W 18(UO 2) 2{(H 2O) 3Zn} 2O 68] 10− ( 1d) give two-line P NMR spectra that are consistent with a C s 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 C i symmetry of solid-state structures. The uranium atoms have pentagonal-bipyramidal coordination, achieved by three equatorial bonds to the one XW 9 and two bonds to the other. The M atoms have octahedral or square pyramidal coordination, but only one bond to the one XW 9 and one bond to the other.