Die Kristallstrukturen der Dicaesium‐Dodekahalogeno‐closo‐Dodekaborate Cs₂[B₁₂X₁₂] (X = Cl, Br, I) und ihrer Hydrate

Abstract

Inhaltsübersicht. Durch Reaktionen von Cs 2 [B 12 H 12 ] mit den entsprechenden elementaren Halogenen (Cl 2 , Br 2 bzw. I 2 ) wurden die perhalogenierten Derivate Cs 2 [B 12 X 12 ] (X ϭ Cl Ϫ I) erhalten. Beim Umkristallisieren aus wäßriger Lösung fielen dabei zunächst die Dihydrate (Cs 2 [B 12 X 12 ] · 2 H 2 O) in Form von farblosen, polyederförmigen Einkristallen an, die sich unter Erhalt ihrer Kristallinität über die Monohydrate (Cs 2 [B 12 X 12 ] · H 2 O) schließlich topotaktisch zu den wasserfreien Verbindungen (Cs 2 [B 12 X 12 ]) dehydratisieren lassen. Mittels Röntgenbeugung an Einkristallen war es möglich, die ionischen Caesium-Salze strukturell zu charakterisieren. Alle drei Halogenoborate sind isotyp und kristallisieren bei Raumtemperatur trigonal in der Raumgruppe R3 (Cs 2 [B 12 Cl 12 ]: a ϭ 959,67(3) pm, c ϭ 4564,2(2) pm; Cs 2 [B 12 Br 12 ]: a ϭ 997,92(3) pm, c ϭ 4766,4(3) pm; Cs 2 [B 12 I 12 ]: a ϭ 1047,05(4) pm, c ϭ 5018,3(3) pm; Z ϭ 6). Der Kristallstruktur liegt eine kubisch dichteste Kugelpackung aus zwei kristallographisch unabhängigen quasi-ikosaedrischen [B 12 X 12 ] 2Ϫ -Anionen (Cs 2 [B 12 Cl 12 ]: d(BϪB) ϭ The Crystal Structures of the Dicesium Dodecahalogeno-closo-Dodecaborates Cs 2 [B 12 X 12 ] (X ‫؍‬ Cl, Br, I) and their Hydrates Abstract. The perhalogenated derivatives Cs 2 [B 12 X 12 ] (X ϭ Cl Ϫ I) have been synthesized by reaction of Cs 2 [B 12 H 12 ] with the respective elemental halogens (Cl 2 , Br 2 and I 2 ). Upon recrystallization from aqueous solution colourless, face-rich single crystals of the dihydrates (Cs 2 [B 12 X 12 ] · 2 H 2 O) are obtained first which can be dehydrated topotactically via the monohydrates (Cs 2 [B 12 X 12 ] · H 2 O) leaving to the solvent-free compounds (Cs 2 [B 12 X 12 ]) behind without loss of their crystallinity. The ionic cesium salts were characterized by single crystal X-ray diffraction. All three halogenoborates are isostructural and they crystallize at room temperature in the trigonal space group R3 (Cs 2 [B 12 Cl 12 ]: a ϭ 959.67(3) pm, c ϭ 4564.2(2) pm; Cs 2 [B 12 Br 12 ]: a ϭ 997.92(3) pm, c ϭ 4766.4(3) pm; Cs 2 [B 12 I 12 ]: a ϭ 1047.05(4) pm, c ϭ 5018.3(3) pm; Z ϭ 6). The crystal structures consist of a cubic closest packed host lattice formed by two crystallographically inequivalent quasi-icosahedral [B 12 X 12 ] 2Ϫ anions (Cs 2 [B 12 Cl 12 ]: d(BϪB) ϭ 178 Ϫ 179 pm, d(BϪCl) ϭ 179 Ϫ 180 pm; Cs 2 [B 12 Br 12 ]: d(BϪB) ϭ 176 Ϫ 180 pm, d(BϪBr) ϭ 195 Ϫ 197 pm; Cs 2 [B 12 I 12 ]: d(BϪB) ϭ 177 Ϫ 182 pm, d(BϪI) ϭ 214 Ϫ 217 pm).

K2B12F12: A rare A2X structure for an ionic compound at ambient conditions

“…Similarly, Cs 2 B 12 Cl 12 has a Cs 2 S-like structure [27], Cs 2 (H 2 O)B 12 F 12 has a structure that resembles K 2 B 12 F 12 (this work), and Cs 2 B 12 H 12 has the antifluorite structure [28]. However, the answer is undoubtedly related to the different sizes and shapes of the high-symmetry fluoroanions We are continuing to explore the solid-state structural chemistry of the B 12 F 12 2À anion.…”

“…(The ''radius'' 3.083 Å can also be compared with one-half of the ClÁ Á ÁCl diameter of the B 12 Cl 12 2À anion, ca. 3.5 Å[27].) The effective volume of B 12 F 12 2À can be estimated, using the procedure of Jenkins et al[34], from the formula unit volume of K 2 B 12 F 12 , 332.0(2) Å 3 , by subtracting twice the volume of K + , 19.7 Å 3 (2 Â 9.86 Å 3 )[34].…”

From an Icosahedron to a Plane: Flattening Dodecaiodo‐dodecaborate by Successive Stripping of Iodine

“…The B 12 I n ( n <12) species discussed here are only accessible by gas‐phase reactions. Our attempts to identify such species in a mixture obtained from Cs 2 B 12 I 12 by controlled thermal decomposition to 30 % weight loss (which finally leads to amorphous material19) failed.…”

The Structure of (H3O)2B12F12·6H2O – a CCP Lattice of B12F122– Anions Intercalated with a Nonplanar Network of O–H···O Connected O6 Rings

“…We have been studying the structures and physicochemical properties of a variety of metal and nonmetal salts of the icosahedral, superweak anion B 12 F 12 2-. [1][2][3][4][5][6][7] Our hypothesis is that the unique combination of size, shape, high symmetry, thermal stability, and extremely weak Brønsted and Lewis basicity of this anion will lead to unanticipated structures and properties [i.e.…”

“…[1][2][3][4][5][6][7] Our hypothesis is that the unique combination of size, shape, high symmetry, thermal stability, and extremely weak Brønsted and Lewis basicity of this anion will lead to unanticipated structures and properties [i.e. unanticipated compared to salts of B 12 H 12 2-, [8][9][10][11] B 12 Cl 12 2-, [12][13][14] B 12 (OH) 12 2-, [15,16] and B 12 (CH 3 ) 12 2- [17] on one hand, and of salts of typical fluoroanions, such as BF 4 -, PF 6 -, Sb 2 F 11 -, SiF 6 2-, and MnF 6 2-, on the other]. For example, K 2 B 12 H 12 exhibits a common antifluorite structure, [10] but K 2 B 12 F 12 exhibits an intermetallic Ni 2 In structure [3] (the B 12 centroids occupy the idealized hexagonal close-packed positions of the In atoms [18] ), which is the first time that this structure has been observed for an ionic compound with a polyatomic anion at ambient temperatures and pressures.…”