Solventothermal synthesis and structure of lamellar alkali metal selenidostannates(IV) A(4)Sn(4)Se(10)center dot xH(2)O with 20-(A = Cs; x=3.2) and 36-membered pores (A = K, Rb; x=4.5, 1.5)

Treatment of A(2)CO(3) (A = K, Rb) with Sn and Se in an H2O/CH3OH mixture a t 130 degrees C affords reaction solutions from which respectively K4Sn4Se1 0. 4.5H(2)O (1) and Rb4Sn4Se10. 1.5H(2)O (2) can be isolated on cooling, 1 crystallizes in the rhombohedral space group R (3) over bar with a=b=15.320 (3)Angstrom, c = 21.019(7)Angstrom, Z= 6, V= 4272(2) Angstrom(3), 2 in the same space group with a=b=15.539(2) Angstrom, c = 21.373(4) Angstrom, Z=6, V= 4469.4(13) Angstrom(3). These isotypic phases contain lamellar (2)(infin ity)[Sn4Se104-] polyanions in which SnSe44- and [Sn2Se6](4-) molecular buil ding units are corner-bridged into a 6(3) net with 36-membered cavities of 1.3x1.4 nm cross-section. Cs4Sn4Se10. 3.2H(2)O (3) can be prepared under si milar mild solventothermal conditions. It crystallizes in the triclinic spa ce group P (1) over bar with a = 7.235(1) Angstrom, b = 9.468(2) Angstrom, 11.235(2) Angstrom, alpha=68.77(3)degrees, beta = 83.25(3)degrees, gamma= 8 4.53(3)degrees, Z= 1, V= 711.2(2) Angstrom(3). I, contrast to the 2-dimensi onal anions of the same formula type in 1 and 2, the (2)(infinity)[Sn4Se10- 4] polyanions of 3 consist of (1)(infinity)[SnSe32-] ribbons that are corne r-bridged through ditetrahedral [Sn2Se6](4-) units into sheets with smaller 20-membered pores, The role of starting pH, cation size and temperature on the construction of lamellar selenidostannates(IV) are discussed. (C) 1999 Academic Press.