The First Examples of Selenidogermanate Salts with Lanthanide Complex Counter Cations: Solvothermal Syntheses and Characterizations of [{ Ln (en) 3 } 2 (μ‐OH) 2 ]Ge 2 Se 6 ( Ln = Eu, Ho) and [{Ho(dien) 2 } 2 (μ‐OH) 2 ]Ge 2 Se 6

The lanthanide selenidogermanates [{Eu(en) 3 } 2 (μ‐OH) 2 ]Ge 2 Se 6 ( 1 ), [{Ho(en) 3 } 2 (μ‐OH) 2 ]Ge 2 Se 6 ( 2 ), and [{Ho(dien) 2 } 2 (μ‐OH) 2 ]Ge 2 Se 6 ( 3 ) (en = ethylenediamine, dien = diethylenetriamine) were solvothermally prepared by the reactions of Eu 2 O 3 (or Ho 2 O 3 ), germanium, and selenium in en and dien solvents respectively. Compounds 1 – 3 are composed of selenidogermanate [Ge 2 Se 6 ] 4– anion and dinuclear lanthanide complex cation [{ Ln (en) 3 } 2 (μ‐OH) 2 ] 4+ ( Ln = Eu, Ho) or [{Ho(dien) 2 } 2 (μ‐OH) 2 ] 4+ . The [Ge 2 Se 6 ] 4– anion is composed of two GeSe 4 tetrahedra sharing a common edge. The dinuclear lanthanide complex cations are built up from two [ Ln (en) 3 ] 3+ or [Ho(dien) 2 ] 3+ ions joined by two μ‐OH bridges. All lanthanide(III) ions are in eight‐coordinate environments forming distorted bicapped trigonal prisms. In 1 – 3 , three‐dimensional supramolecular networks of the anions and cations are formed by N–H ··· Se and N–H ··· O hydrogen bonds. To the best of our knowledge, 1 – 3 are the first examples of selenidogermanate salts with lanthanide complex counter cations.