ARTICLE DOI: 10.1002/zaac.201000458 Synthesis, Crystal and Electronic Structure of [K[18]crown-6)] 2 [Sn 2 Bi 2 ] Felicitas Lips, [a] Marc Raupach, [a] Werner Massa, [a] and Stefanie Dehnen* [a] In Memory of Professor Hans-Georg von Schnering Keywords: Tin; Bismuth; Binary Zintl anions; Pnictido stannates; DFT calculations Abstract. Extraction of an alloy of the nominal composition “KSnBi” by an [18]crown-6 melt, and subsequent by 1,2-diaminoethane (en) resulted in the formation of a new ternary Zintl salt [K([18]crown- 6)] 2 [Sn 2 Bi 2 ](1) comprising the known binary anion [Sn 2 Bi 2 ] 2– . Herein we report synthesis and structure of 1, along with a density functional Introduction Zintl anions in solution are known for more than one century. [1] The first structural report on nine-atom Zintl anions by Kummer and Strähle dates back to 1976. [2] The application of [2.2.2]cryptand as sequestering agent for the alkali metal ions by Corbett and co-workers improved the structural char- acterization of numerous Zintl anions. [3] Recently, the chemis- try of Zintl anions further developed in two important direc- tions. First, access was achieved to endohedral Zintl ions such as [Ni@Pb 10 ] 2– , [4] [M@Pb 12 ] 2– (M = Ni, Pd, Pt), [4] [Pd 2 @Sn 18 ] 4– , [5] or [Ni 3 @(Ge 9 ) 2 ] 4– , [6] which were assigned the term “intermetalloid” clusters. [7] Second, the oxidative coup- ling of nine-atom [Ge 9 ] 4– cluster anions in an ionic liquid re- sulted in a new crystalline germanium modification according to the clathrate-II structure. [8] The reactivity of nine-atom Zintl anions of Group 14 ele- ments, and of seven-atom Zintl anions of Group 15 elements were extensively examined during the last decade. [9] Only re- cently, first reactions of homoatomic [E 14 4 ] 4– or heteroatomic [E 14 2 E 15 2 ] 2– tetrahedral Zintl anions were reported [10] that re- vealed their high synthetic potential. We are interested in the reactivity of binary tetrahedral Zintl anions of main groups 14 and 15 for the formation of ternary intermetalloid clusters. [10b–10e] So far, three types of [E 14 2 E 15 2 ] 2– are known as anions of [K([2.2.2]crypt)] + salts: [Sn 2 Sb 2 ] 2– , [10c] [Sn 2 Bi 2 ] 2– , [11] and [Pb 2 Sb 2 ] 2– . [12] * Prof. Dr. S. Dehnen Fax: +49-6421-2825653 E-Mail: dehnen@chemie.uni-marburg.de [a] Fachbereich Chemie and Wissenschaftliches Zentrum für Materialwissenschaften (WZMW) Philipps-Universität Marburg Hans-Meerwein-Strasse 35043 Marburg, Germany Z. Anorg. Allg. Chem. 2011, 637, 859–863 © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 859 (DFT) study of the anion. The crystal structure of 1 was solved and refined in the cubic space group F23 (no. 196). Unit cell dimensions at 100 K: a = 20.8776(15) Å, V = 9100.0(11) Å 3 [R(int) = 0.0467], final R values R 1 = 0.0521, [I > 2σ(I)], wR 2 = 0.0915 (all data). Herein, we report the synthesis of an alternative, signifi- cantly cheaper Zintl compound [K([18]crown-6)] 2 [Sn 2 Bi 2 ](1), which was obtained upon extraction of an alloy of the nominal composition “KSnBi” by a melt of [18]crown-6 and subse- quent extraction by 1,2-diaminoethane (en) – thus with [18]crown-6 as sequestering agent for the potassium counter- cations beside the known tetrahedral anion. Compound 1 crys- tallizes as large black octahedra (Figure 1). Figure 1. Photo of the crystals of compound 1. The distance of the white bars on the ruler indicate a 1 mm scale. The employment of [18]crown-6 for the crystallization of Zintl anions from solution is much less common than the use of [2.2.2]cryptand. However, some prominent examples are ol- igomeric [Ge 9 =Ge 9 =Ge 9 =Ge 9 ] 8– , initially characterized with [Rb([18]crown-6)] + counteractions, [13] [K([18]crown- 6)] 2 [Ge 9 ]·en with an infinite chain of doubly-bonded [Ge 9 ] 2– clusters, [14] and [Rb([18]crown-6)] 2 [K([18]crown- 6)] 2 Rb 4 [{Ni(CO) 2 } 2 (μ-Si 9 ) 2 ]·22NH 3 , a coordination compound of two [Si 9 ] 3– anions connected to two Ni(CO) 2 units. [15] Fur- thermore, [18]crown-6 was used as reaction medium for the one-pot synthesis of [K 4 Sn 9 ([18]crown-6) 3 ]·en starting out from the elements. [16]