Das Lanthan‐Dodekahydro‐ closo ‐Dodekaborat‐Hydrat [La(H 2 O) 9 ] 2 [B 12 H 12 ] 3 ·15 H 2 O und sein Oxonium‐Chlorid‐Derivat [La(H 2 O) 9 ](H 3 O)Cl 2 [B 12 H 12 ]·H 2 O

The Lanthanum Dodecahydro‐ closo ‐Dodecaborate Hydrate [La(H 2 O) 9 ] 2 [B 12 H 12 ] 3 ·15 H 2 O and its Oxonium‐Chloride Derivative [La(H 2 O) 9 ](H 3 O)Cl 2 [B 12 H 12 ]·H 2 O By neutralization of an aqueous solution of the free acid (H 3 O) 2 [B 12 H 12 ] with basic La 2 O 3 and after isothermic evaporation colourless, face‐rich single crystals of a water‐rich lanthanum(III) dodecahydro‐ closo ‐dodecaborate hydrate [La(H 2 O) 9 ] 2 [B 12 H 12 ] 3 ·15 H 2 O are isolated. The compound crystallizes in the trigonal system with the centrosymmetric space group $P{\bar 3}c$ ( a = 1189.95(2), c = 7313.27(9) pm, c/a = 6.146; Z = 6; measuring temperature: 100 K). The crystal structure of [La(H 2 O) 9 ] 2 [B 12 H 12 ] 3 ·15 H 2 O can be characterized by two of each other independent, one into another posed motives of lattice components. The [B 12 H 12 ] 2− anions (d(B–B) = 177–179 pm; d(B–H) = 105–116 pm) are arranged according to the samarium structure, while the La 3+ cations are arranged according to the copper structure. The lanthanum cations are coordinated in first sphere by nine oxygen atoms from water molecules in form of a threecapped trigonal prism (d(La–O) = 251–262 pm). A coordinative influence of the [B 12 H 12 ] 2− anions on La 3+ has not been determined. Since “zeolitic” water of hydratation is also present, obviously the classical H–O δ– ··· +δ H–O‐hydrogen bonds play a significant role in the stabilization of the crystal structure. During the conversion of an aqueous solution of (H 3 O) 2 [B 12 H 12 ] with lanthanum trichloride an anion‐mixed salt with the composition [La(H 2 O) 9 ](H 3 O)Cl 2 [B 12 H 12 ]·H 2 O is obtained. The compound crystallizes in the hexagonal system with the non ‐centrosymmetric space group $P{\bar 6}c {\rm 2}$ ( a = 808.84(3), c = 2064.51(8) pm, c/a = 2.552; Z = 2; measuring temperature: 293 K). The crystal structure can be characterized as a layer‐like structure, in which [B 12 H 12 ] 2− anions and H 3 O + cations alternate with layers of [La(H 2 O) 9 ] 3+ cations (d(La–O) = 252–260 pm) and Cl − anions along [001]. The [B 12 H 12 ] 2− (d(B–B) = 176–179 pm; d(B–H) = 104–113 pm) and Cl − anions exhibit no coordinative influence on La 3+ . Hydrogen bonds are formed between the H 3 O + cations and [B 12 H 12 ] 2− anions, also between the water molecules of [La(H 2 O) 9 ] 3+ and Cl − anions, which contribute to the stabilization of the crystal structure.