Synthesis, crystal structures and properties of the polychalcogenides manganese-tris(1,2-ethanediamine)-triselenide [Mn(en)(3)]Se-3 and manganese-tris(1,2-ethanediamine)-monotellurodiselenide [Mn(en)(3)]TeSe2

The reaction of manganese(II)-chloride-tetrahydrate, caesium triselenide an d elemental selenium or tellurium in 1,2-ethanediamine (en) under solvother mal conditions leads to the formation of two new isostructural compounds [M n(en)(3)]Se-3 (1) and [Mn(en)(3)]TeSe2 (2). The compounds crystallize in th e orthorhombic space group Pbcn with the lattice parameters a = 1149.39(9), b = 1506.83(11), c = 935.96(6) pm for 1 and a = 1184.1(2), b = 1495.3(2), c = 949.8(1) pm for 2. Their crystal structures are built up of [Mn(en)(3)] (2+) cations and Se-3(2-) or TeSe22- anions, respectively. Each cation is s urrounded by six next neighbouring anions, and vice versa. Between the cati ons and the anions hydrogen bonding is observed. The thermal behaviour was investigated using differential thermal analysis, thermogravimetry as well as Xray powder diffraction. Completely different properties were found. Com pound 1 decomposes in two distinct endothermic steps, while compound 2 show s only one endothermic peak. The weight loss for 1 corresponds roughly to t he emission of all en molecules, whereas the weight loss for 2 is significa ntly lower. The final products are composed of MnSe2 and elemental Se or Te , respectively, and an unknown crystalline phase which is different for the two samples.