Octanuclear Rare-Earth Clusters

The polyoxo rare-earth core (Ln = Y, Gd, and Yb) has been synthesized from the appropriate rare-earth chloride hydrate and K2Se and Se in dmf (dimethylformamide). The cluster core is ligated with a variety of polyselenido chains in addition to a number of dmf molecules. The structure of the Gd8(dmf)13(μ4-O)(μ3-OH)12(Se3)(Se4)2(Se5)2 cluster, 1, was determined by X-ray diffraction methods. It is similar to an Eu cluster previously characterized. Two new clusters, Yb8(dmf)11(μ4-O)(μ3-OH)12(Se4)2(Se5)2Cl2·dmf, 2, and Y8(dmf)12(μ4-O)(μ3-OH)12(Se4)4Cl2·6 dmf, 3, have also been synthesized and characterized. Clusters 2 and 3 have the same octanuclear core of rare-earth atoms as the Gd cluster but contain two chloro ligands in two isomeric conformations in place of the Se32- ring in the Gd cluster. The geometry of the Ln8 core is described as a triangulated dodecahedron with μ3-OH groups capping the 12 faces. A μ4-O atom centers the cluster with close contacts to four Ln atoms in an approximate tetrahedral arrangement. Pertinent crystallographic data are: Compound 1, monoclinic, , a= 14.410(3) Å, b = 24.439(5) Å, c = 28.927(6) Å, β = 101.05(3)°, V = 9998(3) Å3, T = 106(2) K, Z = 4; Compound 2, orthorhombic, , a = 17.049(9) Å, b = 24.68(1) Å, c = 45.03(2)Å, V = 18,945(16) Å3, T = 153(2) K, Z = 8; Compound 3, monoclinic, C2h5-P21/c, a =18.728(l) Å, b = 29.263( 1) Å, c = 20.548(1) Å, β = 90.144(1)°, V = 11,261(1) Å3, T = 153(2) K, Z = 4.