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)) (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) fragments. Two GeSe(4) tetrahedra are linked through two Se-Se bonds to form a novel Ge(2)Se(8) unit containing a six-membered Ge(2)Se(4) ring in the chair conformation. The Ge(2)Se(8) unit acts as a bridging ligand via the trans terminal Se atoms to interlink the {Ln(tepa)}(2)(μ-OH)(2) fragments into one-dimensional polymers {Ln(tepa)(μ-OH)}(2)(μ-Ge(2)Se(8)). Compounds 1-3 are the first examples of solvothermally prepared lanthanide complexes with a selenidogermanate anion as a ligand. The Ge(2)Se(6) 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) complex cation. The formation of the Ge(2)Se(8) and Ge(2)Se(6) anions and their behavior towards lanthanide ions in 1-4 show the significant influence of ethylene polyamines on the solvothermal synthesis of Ln selenidogermanates.