The isomorphous substitution of 2H+ for the Cu2+ cation in the complex of bis(aminoguanidine)copper(II): Crystal structures of (Cu0.61H0.78Agu2)B12H12 and (HAgu)2B12H12

An X-ray diffraction study of the (Cu_0.61H_0.78 Agu ₂)B₁₂H₁₂ (I) mixed crystal and one of its components (HAgu)₂B₁₂H₁₂ (II) is performed at 160 K (R = 0.0312 and 0.0345, respectively). Crystals I and II are isostructural. In I, two H⁺ ions partially substitute the Cu²⁺ cation, resulting in a combination of CuAgu ₂]²⁺ and (HAgu ₂)₂₊ cations in the structure. The cations and polyhedral B₁₂H₁₂²⁻ anions have centrosymmetric structures. A square planar environment for the Cu atom is formed by four N atoms of two Agu molecules, which close five-membered chelate cycles Cu-N, 1.9702(13) and 2.0261(10) ?]. The distant apical vertices are occupied by H atoms of the B₁₂H₁₂²⁻ anions Cu…H, 2.805(14) ?]. In the dimeric (HAgu ₂)²⁺ cations, the proton that substitutes for the Cu²⁺ cation forms a three-center N(1)-H…N(4),N(4)′ hydrogen bond which consists of intramolecular and an intermolecular components. In crystal II, the N(1)…N(4) and N(1)…N(4)′ distances 2.685(1) and 3.111(1) ?] are longer than in I 2.610(2) and 3.027(2) ?]. In I, the Cu…H interactions connect CuAgu ₂]²⁺ cations and B₁₂H₁₂²⁻ anions into chains. In the cells that contain the (HAgu ₂)²⁺ dimeric cation, the chains are retained due to the secondary N-H…(B-H) interactions. Numerous weak secondary interactions between the cations and anions form three-dimensional frameworks in structures I and II.