Band 211, Heft 10

A procedure for the direct determination of defect structures is presented. The procedure uses the average structure to calculate starting phases. An iterative cycle of inverse Fourier transforms and interpretations of the scattering density is applied. Within each cycle the scattering density is interpreted to yield a structure deviating from the average structure by missing, replaced or shifted atoms. The procedure usually converges after a few cycles and allows a direct determination of substitutional and displacement disorder. By analyzing the correlations between different atoms, extended defects can be recognized. The current results are preliminary and have been limited to an idealized one dimensional situation, under the assumption of a negligible experimental resolution function.

β –MnSO 3 · 3 D 2 O, M r = 195.078, orthorhombic, P 2 1 2 1 2 1 , a = 9.7668(12) Å, b = 5.6373(7) Å, c = 9.5598(10) Å, V = 526.3 Å 3 , Z = 4, D x = 2.46 g cm −3 λ (neutron) = 0.87013 Å, μ = 0.060 cm −1 , F (000) = 296 fm, T = 297 K, R = 0.07, wR = 0.024, S 2 = 1.07 (0.04), 6303 measured, 1348 unique intensities, 229 refined parameters, refinement on | F | 2 including weak and negative intensities. The intensities are shown to be normally and independently distributed and their variances to be properly determined. A simple model is applied to take weakening by extinction into account. Anharmonic motion of two O and two D atoms up to the fourth order of a Gram-Charlier expansion was refined. One of these two O forms very long hydrogen bonds (3.02 Å–3.16 Å).

The intermediate part of the cation substitution series (Ca 1− x Sr x ) 8 [Al 12 O 24 ](WO 4 ) 2 of the aluminate sodalites Ca 8 [Al 12 O 24 ](WO 4 ) 2 and Sr 8 [Al 12 O 24 ](WO 4 ) 2 has been studied as a function of temperature and composition, with emphasis on the range 0.50 ≤ x ≤ 0.60. A composition-induced phase transition occurs at x ≈ 0.56 at room temperature and a temperature-induced phase transition from tetragonal to possibly cubic on cooling was observed below room temperature. A tentative x – T phase diagram is given.

Bisferrocenium hexadecaiodide (bis-dicyclopentadienyliron(III)hexadecaiodide) [Cp 2 Fe] 2 I 16 (Cp = η 5 -C 5 H 5 ) has been prepared in acetonitrile by reaction of ferrocenium triiodide and excess iodine in the molar ratio of 1:14. It crystallizes at 293 K in the triclinic space group P [unk] with a = 11.558(3) Å, b = 11.877(3) Å, c = 18.754(6) Å, α = 102.13(2)°, β = 100.99(2)°, γ = 107.72(3)°, V = 2306(1) Å 3 and Z = 2. The crystal structure has been refined by full matrix least-squares procedures to R ( F ) = 0.0546 for 5525 reflections. Bisferrocenium hexadecaiodide contains nets of hexadecaiodide units forming channels along [110] filled by columns of disordered complex cations (Cp 2 Fe) + .

The crystal structures of (PPh 3 )HgRe 2 ( μ -acPh)( μ -PCy 2 )(CO) 6 1 and (PPh 3 )HgRe 2 ( μ -PCy 2 ) Cl(CO) 7 2 (Cy = cyclohexyl) exhibit both a HgRe 2 triangular metal core with an exocyclic PPh 3 ligand attached to Hg. 1 crystallizes in space group P [unk] with a = 9.703(2) Å, b = 10.484(3) Å, c = 21.526(6) Å, α = 86.46(2)°, β = 84.26(2)°, γ = 81.65(2)°, V = 2153(1) Å 3 . The metal – metal bond lengths are Re – Re 3.060(1) Å, Hg – Re 2.757(1) Å and Hg – Re 2.765(1) Å. Compound 2 crystallizes in space group P 2 1 / n with a = 15.134(4) Å, b = 9.623(4) Å, c = 27.273(9) Å, β = 92.42(2)°, V = 3967(2) Å 3 . Bond lengths are Re – Re 3.254(1) Å, Hg – Re 2.770(1) Å and Hg – Re 2.786(1) Å.