Conformation isomerism of nonagermanide ions.: Crystal structures of brown and red [K-([2.2.2]crypt)]6Ge9Ge9•(ethylenediamine)x (x = 0.5, 1.5)

A brown and a red form of the [K-([2.2.2]-crypt)](+) salts of naked polyhedral nonagermanide anions were isolated by dissolving the alloy K4Ge9 in ethylenediamine. The compounds [K-([2.2.2]crypt)](6)Ge9Ge9.(ethylenediamine)(x) with x = 0.5 (2a, brown) and 1.5 (2b, red) crystallize in the P (1) over bar space group with two independent cluster anions and six [K-([2.2.2]-crypt)](+) units. The structures are almost isotypic, but differ by their cell parameters at 233 K (2a, a = 14.397(1) Angstrom, b = 19.765(2) Angstrom, c = 28.898(2) Angstrom, alpha = 87.485(9)degrees, beta = 79.168(9)degrees, gamma = 85.415(8)degrees; 2a, 14.503(1) Angstrom, b = 19.924(2) Angstrom, c = 28.935(3) Angstrom, alpha = 87.43(1)degrees, B = 80.85(1)degrees, gamma = 85.92(1)degrees) and atomic parameters. The differences arise with two additional ethylenediamine molecules in the case of red 2b. These solvent molecules were refined at 50% occupancy. The solvent molecules have a significant influence on the color of the crystals and the conformation of the deltahedral anions. The structures of the clusters correspond to C-2v distorted polyhedra that lie between the D-3h tricapped trigonal prism and the C-4v monocapped square antiprism. A geometrically deduced charge allocation Ge-9(2-) and Ge-9(4-) in an earlier study of a red compound with x = 2.5 and a less accurate structure refinement are not supported by the structures of the anions. EPR measurements on a single crystal of 2a reveal paramagnetic properties and presumably equal 3- charges fur each of the two independent anions.