Powder and single-crystal X-ray diffraction study of the structure of [Y(H2O)]2(C2O4)(CO3)2

From powder pattern indexing it has been demonstrated that [Y(H2O)](2)(C2O4)(CO3)(2), yttrium oxalate carbonate, crystallizes with orthorhombic symmetry, space group C222(1), a = 7.8177 (7), b = 14.943 (1), c = 9.4845 (7) Angstrom, V = 1108.0 (1) Angstrom (3\), Z = 4. This unit cell displays a doubling of the c parameter, arising from weak diffraction lines observed in the powder diffraction pattern, with respect to results reported in the literature. The crystal structure has been solved ab initio using direct methods from powder data and has been confirmed by additional single-crystal data collected with a CCD area detector. The overall crystal structure is similar for both unit cells, except that an alternation of the carbonate groups in the direction parallel to the screw axis is displayed in the larger cell, while with the suggested half unit cell (space group C2mm) the carbonate groups would show only one orientation. The unit-cell determination strategy from single-crystal diffraction, collected with Nonius CAD-4 and Nonius Kappa CCD diffractometers, is discussed with respect to the results extracted from the powder diffraction pattern. The study demonstrates the power and usefulness of the full trace of a powder pattern for the detection of subtle structure details.