Solvothermal Synthesis and Structures of Lamellar [Mn(tren)₂]Cl₂ and the Dimeric and Polymeric Hexaselenidomanganese(II) Complexes [{Mn(Se₆)(tren)}₂] and $^{2}_{\infty}\rm [\{Mn(Se_{6})(tren)\}]$

Reaction of [MnCl₂(tren)] with tren (tris‐(2‐aminoethyl)amine) affords the coordination polymer $^{2}_{\infty}\rm [Mn(tren)_{2}]Cl_{2}$ (1), in which the primary amino groups of tridentate tren ligands connect [(tren)Mn]²⁺ fragments into a pseudo 6³ network. The Mn atoms exhibit a capped octahedral environment with the tertiary N atom of the second tetradentate tren ligand in the capping position. Treatment of MnCl₂ with Se at 1:2 molar ratio in H₂O/tren (10:1) at 150 °C leads to formation of the dinuclear complex [{Mn(μ‐Se₆)(tren)}₂] (2), which contains tetradentate tren ligands and two bridging hexaselenide ligands in the 1κSe¹ : 2κSe⁶ mode. In contrast, reaction of [MnCl₂(tren)] with Se at a 1:6 molar ratio under similar sovothermal conditions affords the isomeric coordination polymer $^{2}_{\infty}\rm [Mn(\mu-Se_{6})(tren)]$ (3). In this complex, Se₆²⁻ anions now bridge [(tren)Mn]²⁺ fragments into chains, that themselves are linked into polymeric sheets through one of the primary amino groups of the tetradentate tren ligands.