[Sb11]3- and [As11]3-:: Synthesis and crystal structure of two new ammoniates containing trishomocubane-like polyanions

The ammoniates [K(18-crown-6)(NH3)(2)](3)Sb-11 center dot 5.5NH(3) (1) and [Cs(18-crown-6)](2)CsAs11 center dot 8NH(3) (2) (18-crown-6 = 18C6: 1,4,7,10,13,16-Hexaoxacyclooctadecan) were synthesized by either the reaction of K3Sb7 with SbPh3 in liquid ammonia or by extraction Of Cs3As11 with liquid ammonia. Single crystals were isolated and characterized by low temperature X-ray structure analysis. [K(18-crown-6)(NH3)(2)](3)Sb-11 center dot 5.5NH(3) crystallizes in the space group P (1) over bar with a = 13.31(2) angstrom, b = 15.161(2) angstrom, c = 22.521(3) angstrom, alpha = 99.23(t)degrees, beta = 100.99(1)degrees and gamma = 105.03(l)degrees. [Cs(18-crown- 6)](2)CsAs11 center dot 8NH(3) crystallizes in the monoclinic space group C2/c with a = 20.009(3) angstrom, b = 17.024(l) angstrom, c = 19.838(2) angstrom and beta = 119.732(9)degrees. While 1 contains isolated [Sb-11](3-) anions and [K(18-crown-6)(NH3)(2)](+) complexes, cesium-arsenic contacts lead to one-dimensionally infinite [CsAs11](2-) chains in 2.