The first μ-Ge2Se8 ligand to lanthanide(III) centers: solvothermal syntheses and characterizations of lanthanide selenidogermanate complexes with a pentadentate polyamine as a co-ligand.

Solvothermal reactions of elements Ge and Se with Ln(2)O(3) in a pentadentate polyamine, tetraethylenepentamine (tepa), produced novel neutral lanthanide-selenidogermanate polymers [{Ln(tepa)(μ-OH)}(2)(μ-Ge(2)Se(8))](n) (Ln = Eu 1, Gd 2, Dy 3). The reaction with Dy(2)O(3) in ethylenediamine (en) afforded an ionic selenidogermanate [{Dy(en)(3)}(2)(μ-OH)(2)]Ge(2)Se(6) (4). In compounds 1-3, the Ln(3+) ions are coordinated by a tepa and two OH(-) ligands to form binuclear [{Ln(tepa)}(2)(μ-OH)(2)](4+) fragments. Two GeSe(4) tetrahedra are linked through two Se-Se bonds to form a novel [Ge(2)Se(8)](4-) unit containing a six-membered Ge(2)Se(4) ring in the chair conformation. The [Ge(2)Se(8)](4-) unit acts as a bridging ligand via the trans terminal Se atoms to interlink the [{Ln(tepa)}(2)(μ-OH)(2)](4+) fragments into one-dimensional polymers [{Ln(tepa)(μ-OH)}(2)(μ-Ge(2)Se(8))](n). Compounds 1-3 are the first examples of solvothermally prepared lanthanide complexes with a selenidogermanate anion as a ligand. The [Ge(2)Se(6)](4-) anion in 4 is composed of two GeSe(4) tetrahedra sharing a common edge, and is charge compensated by a [{Dy(en)(5)}(2)(μ-OH)(2)](4+) complex cation. The formation of the [Ge(2)Se(8)](4-) and [Ge(2)Se(6)](4-) anions and their behavior towards lanthanide ions in 1-4 show the significant influence of ethylene polyamines on the solvothermal synthesis of Ln selenidogermanates.