Octakis(dimethylammonium) hexa-mu2-chlorido-hexachloridotrinickelate(II) dichloride: a linear trinickel complex with asymmetric bridging.

The title compound, (C2H8N)8[Ni3Cl12]Cl2, crystallizes as linear [Ni3Cl12]6- complex anions with inversion symmetry, separated from one another by dimethylammonium cations and noncoordinated chloride ions. The gross structural arrangement of the trinickel complex is as a segment of face-sharing NiCl6 octahedra similar to the (NiCl3)n chains of CsNiCl3-type compounds. On closer inspection, the regular coordination geometry of the complex consists of octahedral NiCl6 in the center linked by two symmetrically bridging chloride ions to square-pyramidal NiCl5 on each end. A long semicoordinate bond is formed by each of the terminal Ni(II) cations, to give a 5+1 coordination geometry and form an asymmetric bridge to the central Ni(II) cation. The dimethylammonium cations surround the complex with an extensive hydrogen-bonding network, linking the complex to the noncoordinated chloride ions. Asymmetric bridging in the complex arises from short hydrogen bonds from the same dimethylammonium cation to the apical and asymmetric bridging chloride ions, causing the complex to scissor outward.