PREPARATION AND CRYSTAL-STRUCTURE OF ETHYLENEDIAMMONIUM SELENOSTANNATES(IV) AND [2SNSE2.EN]INFINITY

The selenostannates(IV) [enH2]2[Sn2Se6] . en 1 and [enH2][Sn3Se7] . 1/ 2en 2 have been prepared by the methanolothermal reaction of SnSe2 wit h ethylenediamine (en) (160-degrees-C, 13 bar) in the presence of resp ectively Se or BaSe. The [Sn2Se6]4- anion in 1 consists of two edge-br idged SnSe4 tetrahedra and displays crystallographic C(i) symmetry. Th e crystal structure of 2 contains polyselenostannate(IV) sheet anions [Sn2Se72-]infinity2, for which the basic elements are trigonal SnSe5 b ipyramids. Each of the three symmetry independent Sn atoms is linked t o the other Sn atoms via Sn-Se-Sn bridges leading to the formation of Sn3Se10 units. Methanolothermal reaction of SnSe2 with en alone yields the edge-bridged chain structure [2SnSe2 . en]infinity in which each of the Sn atoms is bonded to four Se atoms. Every second Sn atom is al so coordinated by an en molecule and displays, therefore, an octahedra l geometry. The remaining Sn atoms are coordinated tetrahedrally by Se atoms.