Conformation Isomerism of Nonagermanide Ions. Crystal Structures of Brown and Red [K-([2.2.2]crypt)]6Ge9Ge9·(ethylenediamine)x (x = 0.5, 1.5)

Publisher Website
Google Scholar
Abstract
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)]6Ge9Ge9·(ethylenediamine)x with x = 0.5 (2a, brown) and 1.5 (2b, red) crystallize in the P1̄ 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) Å, b = 19.765(2) Å, c = 28.898(2) Å, α = 87.485(9)°, β = 79.168(9)°, γ = 85.415(8)°; 2a, a = 14.503(1) Å, b = 19.924(2) Å, c = 28.935(3) Å, α = 87.43(1)°, β = 80.85(1)°, γ = 85.92(1)°) 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 C2v distorted polyhedra that lie between the D3h tricapped trigonal prism and the C4v monocapped square antiprism. A geometrically deduced charge allocation Ge92- and Ge94- 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 for each of the two independent anions.

This publication has 19 references indexed in Scilit: