Synthesis and structure of [Sn4Se11](6-), (1)(infinity)[Sn2Se52-], and (1)(infinity)[Sn3Se72-] - Model anions for the solventothermal reaction pathway to lamellar selenidostannates(IV)

Reaction of A(2)CO(3) (A = K, Rb) with Sn and Se in an H2O/CH3OH mixture at 115-130 degrees C affords the isotypic selenidostannates(IV) A(6)Sn(4)Se(1 1) . xH(2)O (A = K, x = 8) 1 and 2 whose discrete [Sn4Se11](6-) anions each contain two corner-bridged ditetrahedral [Sn2Se6](4-) species. Similar rea ction conditions with A = Cs afford Cs2Sn2Se5 . H2O (3 a) and Cs2Sn2Se5 (3 b) in which such [Sn2Se6](4-) building blocks are connected through common Se atoms into infinite (infinitySn2Se52-)-Sn-2] chains. The (1)(infinity)[S n3Se72-] ribbons of (Et4N)(2)Sn3Se7 (4), formed by treating (Et4N)I with Sn and Se in methanol at 130 degrees C, can be regarded as resulting from the condensation of (2)(infinity)[Sn2Se52-] chains with molecular [SnSe4](4-) anions. The anions [Sn4Se11](6-) (1)(infinity)[Sn2Se52-] and (1)(infinity)[ Sn3Se72-] represent the products of individual reaction steps on the potent ial condensation pathway of [Sn2Se6](4-) to the lamellar selenidostannates (IV) (2)(infinity)[Sn4Se92-] or (2)(infinity)[Sn3Se72-].