Das Lanthan-Dodekahydro-closo-Dodekaborat-Hydrat [La(H2O)9]2[B12H12]3·15 H2O und sein Oxonium-Chlorid-Derivat [La(H2O)9](H3O)Cl2[B12H12]·H2O†
Professor Heinrich Nöth zum 80. Geburtstag gewidmet
Abstract
The Lanthanum Dodecahydro-closo-Dodecaborate Hydrate [La(H2O)9]2[B12H12]3·15 H2O and its Oxonium-Chloride Derivative [La(H2O)9](H3O)Cl2[B12H12]·H2O
By neutralization of an aqueous solution of the free acid (H3O)2[B12H12] with basic La2O3 and after isothermic evaporation colourless, face-rich single crystals of a water-rich lanthanum(III) dodecahydro-closo-dodecaborate hydrate [La(H2O)9]2[B12H12]3·15 H2O are isolated. The compound crystallizes in the trigonal system with the centrosymmetric space group 
(a = 1189.95(2), c = 7313.27(9) pm, c/a = 6.146; Z = 6; measuring temperature: 100 K). The crystal structure of [La(H2O)9]2[B12H12]3·15 H2O can be characterized by two of each other independent, one into another posed motives of lattice components. The [B12H12]2− anions (d(B–B) = 177–179 pm; d(B–H) = 105–116 pm) are arranged according to the samarium structure, while the La3+ 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 [B12H12]2− anions on La3+ has not been determined. Since “zeolitic” water of hydratation is also present, obviously the classical H–Oδ–···+δH–O-hydrogen bonds play a significant role in the stabilization of the crystal structure. During the conversion of an aqueous solution of (H3O)2[B12H12] with lanthanum trichloride an anion-mixed salt with the composition [La(H2O)9](H3O)Cl2[B12H12]·H2O is obtained. The compound crystallizes in the hexagonal system with the non-centrosymmetric space group 
(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 [B12H12]2− anions and H3O+ cations alternate with layers of [La(H2O)9]3+ cations (d(La–O) = 252–260 pm) and Cl− anions along [001]. The [B12H12]2− (d(B–B) = 176–179 pm; d(B–H) = 104–113 pm) and Cl− anions exhibit no coordinative influence on La3+. Hydrogen bonds are formed between the H3O+ cations and [B12H12]2− anions, also between the water molecules of [La(H2O)9]3+ and Cl− anions, which contribute to the stabilization of the crystal structure.
