Structural studies of salts of cis and trans ì-fluoro-bridged polymers of GeF₅^- and of the GeF₅^- Monomer

XeF₅⁺GeF₅^- is orthorhombic, and at 20 ◦C a₀ = 7.119 (2) Å,b₀= 12.986 (4) Å, c₀ = 7.398 (1) Å, and V = 683.9 (5) ų; Z = 4, and the space group is Pmnb (a nonstandard setting of Pnma, No. 62). From 437 independent X-ray diffraction data, the structure was refined to a weighted R of 0.018 (unweighted R = 0.021) with a standard deviation in an observation of unit weight of 0.725. The structure contains infinite chains of GeF₆ octahedra sharing trans vertices. The XeF₅ cations are arranged alternately to left and right along the chain such that each cation approaches symmetrically two of the μ-fluoro-bridged GeF₆ units. The nonbridging GeF₄units are planar and approximately square, with Ge-F =1.75 (2) Å. The f-bridging Ge-Fdistance is 1.890 (1) Å. ClO₂+GeF₅^- is orthorhombic, and at-105 ± 10 ◦C a₀ = 14.64(2) Å, 60 = 7.576 (1) Å, c₀ = 8.894 (2) Å, and V = 987.0 (4) ų; Z = 8, and the space group is C222₁ (No. 20). From 645 independent X-ray diffraction intensitydata, refinement led to convergence with a weighted R factor of 0.068 (unweighted R = 0.059)and a standard deviation in an observation of unit weight of 3.938. In the structure, infinite chains of approximately octahedral GeF6 units are joined by sharing cis vertices. This isan infinite helix having all Ge atoms of the chain nearly coplanar. The nonbridging Ge-F distances are in two sets, the shorter (Ge-F = 1.737 (4) and 1.728 (3) A) being cis to the bridging Ge-F bonds and the longer (Ge-F = 1.776 (3) and 1.768 (3) Å) being trans to the Ge-F bridging. The two μ-bridging Ge-F distances are not significantly different, at 1.887 (1) Å. The anion chains are held together by interactions with the cations. There are two crystallographically distinguishable ClO₂⁺ units. Each lies on a twofold axis, and the closest cation to anion contacts (Cll-Fl = 2.539 (3) A; C₁₂-F₄ = 2.625 (3) ÅC12-F4 = 2.625 (3) Å) involve approach of F to Cl normal to the C1O₂ triangle. Infrared and Raman spectra of the XeF₅⁺GeF₅^- and C1O₂⁺GF₅^- salts have been assigned. Similarities of the vibrational spectra of the latter to the spectra of the O₂⁺ salt indicate that the same anion occurs in both. The vibrational data show that a third oligomeric form of the anion must occur in the NO₂⁺, NF₄⁺, and SF₃⁺ salts. The tetrabutylammonium salt contains a monomeric anion of approximately D_3h symmetry.