Chapter 4 - Jacobs University

Chapter 9
Unpublished Results
9.2.4.1 X-ray crystallography
A block crystal of 18a with dimensions 0.32 x 0.18 x 0.06 mm 3 was mounted in a Hampton
cryoloop for indexing and intensity data collection at 173 K on a Bruker D8 APEX II CCD
single-crystal diffractometer using Mo Kα radiation (λ = 0.71073 Å). Of the 130560 reflections
collected (2θ max = 28.17°, 99.4% complete), 12040 were unique (R int = 0.1377) and 6180
reflections were considered observed (I > 2σ (I)). Routine Lorentz and polarization corrections
were applied and an absorption correction was performed using the SADABS program
(Sheldrick, G. M.; Acta Crystallogr. 2007, A64, 112). Direct methods were used to locate the
tungsten and yttrium atoms (SHELXS-97). Then the remaining atoms were found from
successive Fourier maps (SHELXL-97). The final cycle of refinement, including the atomic
coordinates, anisotropic thermal parameters (W, Y, Ge, K and Na atoms) and isotropic thermal
parameters converged at R = 0.0593 (I > 2σ(I)) and and Rw = 0.1611 (all data). In the final
difference map the deepest hole was -3.2 e - Å-3 and the highest peak 6.1 e - Å-3. The data for this
crystal are summarized in Table 9.5.
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