Crystal structures of cesium and dimethylammonium cupradecaborates, Cs[CuB10H10] and (CH3)2 NH2[CuB10H10]

The crystal structures of CsCuB₁₀H₁₀] (I) and (CH₃)₂NH₂CuB₁₀H₁₀] (II) are studied (R = 0.0398 and 0.0510 for 1225 and 2728 observed reflections in I and II, respectively). Crystals I and II are built of (CuB₁₀H₁₀)^?]∞ anionic chains and cations. The distorted tetrahedral coordination of the Cu⁺ ions is formed by four pairs of B-H atoms from two polyhedral anions. The Cu-B bond lengths in I and II are 2.159–2.287(6) and 2.130–2.285(9) Å, respectively. The coordination of the Cu⁺ ions in II includes only edges between apical and equatorial vertices of the anions. In I, both the edges of the apical belt and those between two equatorial vertices are involved in coordination. The ability of the B₁₀H ₁₀ ^2? anion to coordinate metals by the equatorial edge is established for the first time.