Synthesis and Structural Characterization of the 28-Isopolytungstate Fragment [H2W28O95]20– Stabilized by Two External Lanthanide Ions [Ln2(H2O)10W28O93(OH)2]14–

摘要

The V-shaped polyanions [Ln2(H2O)10W28O93(OH)2]14– [Ln = Sm (1), and Eu (2)] have been synthesized by reaction of Ln3+ and WO4 2– in aqueous acidic medium. The sodium salt of 1 and the mixed sodium-europium salt of 2 have been characterized in the solid state by FTIR, single-crystal XRD, thermogravimetric analysis (TGA), and elemental analysis. Singlecrystal X-ray analyses were carried out on Na14[Sm2(H2O)10- W28O93(OH)2]·40H2O (Na-1) which crystallizes in the triclinic system, space group P1ˉ, a = 14.8727(6) A, b = 21.7762(11) A, c = 23.5751(10) A, a = 89.175(2)°, β = 86.430(2)°, γ = 75.364(2)°, andZ=2 and onNa8Eu2[Eu2(H2O)10W28O93(OH)2]· 47H2O (NaEu-2) which crystallizes in the monoclinic system, space group P21, a = 25.3862(11) A, b = 14.6364(5) A, c = 40.3264(16) A, β = 96.107(3)°, and Z = 4. The polyanions 1and 2 consist of a novel isopolyanion unit [H2W28O95]20– and two {Ln(H2O)n}3+ supporting groups. The {W28} cluster coordinates to the two Ln3+ ions and acts as a tri- and tetradentate ligand for the two lanthanide ions. The {W28} cluster consists of two undecatungstate {W11} fragments and a hexatungstate fragment {W6}. Furthermore, in the solid state, one {W28} fragment is connected to another {W28} via lanthanide-oxo bridges forming a {W56} aggregate ([Ln2(H2O)10W28O93- (OH)2]14–)2. It was also possible to synthesize other lanthanide derivatives of the {W28} cluster (Ln = La, Ce, Pr, Nd, and Gd) as determined by FTIR and preliminary single-crystal Xray diffraction data.