NEUTRON AND X-RAY-DIFFRACTION STRUCTURE DETERMINATION OF CS2[VOF4(H2O)], A COMPOUND PREVIOUSLY ASSIGNED CS2VF6 COMPOSITION

The crystal structure of Cs2[VOF4(H2O)] has been studied on the basis of three-dimensional neutron and X-ray diffraction data. The structure is orthorhombic; a = 15.251(2), b = 6.486(1), and c = 7.010(1) Å; Z = 4; V = 693.46 Å3; space group Ccmm (No. 63). From the neutron data the positions of all atomic species except vanadium were refined. The final Rw value was 0.030 for 427 independent reflections with σ(I) I ≤ 0.60. In the X-ray case the positions of nonhydrogen atoms were refined. The final Rw value was 0.022 for 509 observations with σ(I) I ≤ 0.40. The structure contains strongly deformed octahedral complex ions [VOF4(H2O)]2-, held together by hydrogen bonds OHF (forming chains in the c direction) with cesium atoms inserted between them. The vanadyl ion VO2+ (VO) bond distance 1.602(8) Å; X-ray value) is coordinated to four fluorine ligands and to one H2O molecule in trans position to the vanadyl oxygen. The VF and the VOw distances are 4 × 1.919(4) and 2.268(8) Å, respectively; all are X-ray values. The OH distance is 0.987(7) Å and the HOwH angle 105.1(9)°. The coordination numbers of the two crystallographically independent cesium atoms are 13 and 11, respectively. © 1979.