Zu den Kristallstrukturen der Übergangsmetall(II)‐Dodekahydro‐ closo ‐Dodekaborat‐Hydrate Cu(H 2 O) 5,5 [B 12 H 12 ]·2,5 H 2 O und Zn(H 2 O) 6 [B 12 H 12 ]·6 H 2 O

On the Crystal Structures of the Transition‐Metal(II) Dodecahydro‐ closo ‐Dodecaborate Hydrates Cu(H 2 O) 5.5 [B 12 H 12 ]·2.5 H 2 O and Zn(H 2 O) 6 [B 12 H 12 ]·6 H 2 O By neutralization of an aqueous solution of the free acid (H 3 O) 2 [B 12 H 12 ] with basic copper(II) carbonate or zinc carbonate, blue lath‐shaped single crystals of the octahydrate Cu[B 12 H 12 ]·8 H 2 O (≡ Cu(H 2 O) 5.5 [B 12 H 12 ]·2.5 H 2 O) and colourless face‐rich single crystals of the dodecahydrate Zn[B 12 H 12 ]·12 H 2 O (≡ Zn(H 2 O) 6 [B 12 H 12 ]·6 H 2 O) could be isolated after isothermic evaporation. Copper(II) dodecahydro‐ closo ‐dodecaborate octahydrate crystallizes at room temperature in the monoclinic system with the non ‐centrosymmetric space group Pm (Cu(H 2 O) 5.5 [B 12 H 12 ]·2.5 H 2 O: a = 768.23(5), b = 1434.48(9), c = 777.31(5) pm, β = 90.894(6)°; Z = 2), whereas zinc dodecahydro‐ closo ‐dodecaborate dodecahydrate crystallizes cubic in the likewise non ‐centrosymmetric space group F 23 (Zn(H 2 O) 6 [B 12 H 12 ]·6 H 2 O: a = 1637.43(9) pm; Z = 8). The crystal structure of Cu(H 2 O) 5.5 [B 12 H 12 ]·2.5 H 2 O can be described as a monoclinic distortion variant of the CsCl‐type arrangement. As characteristic feature the formation of isolated [Cu 2 (H 2 O) 11 ] 4+ units as a condensate of two corner‐linked Jahn‐Teller distorted [Cu(H 2 O) 6 ] 2+ octahedra via an oxygen atom of crystal water can be considered. Since “zeolitic” water of hydratation is also present, obviously both classical H–O δ− ··· +δ H–O and non ‐classical B–H δ− ··· +δ H–O hydrogen bonds play a significant role for the stabilization of the structure. A direct coordinative influence of the quasi ‐icosahedral [B 12 H 12 ] 2− anions on the Cu 2+ cations has not been determined. The zinc compound Zn(H 2 O) 6 [B 12 H 12 ]·6 H 2 O crystallizes in a NaTl‐type related structure. Two crystallographically different [Zn(H 2 O) 6 ] 2+ octahedra are present, which only differ in their relative orientation within the packing of the [B 12 H 12 ] 2− anions. The stabilization of the crystal structure takes place mainly via H–O δ− ··· +δ H–O hydrogen bonds, since again the hydrogen atoms of the [B 12 H 12 ] 2− anions have no direct coordinative influence on the Zn 2+ cations.