The decomposition of the layered double hydroxides of Co and Al: phase segregation of a new single phase spinel oxide.

Monophasic Co-Al-CO3-like layered double hydroxides has been prepared by the coprecipitation method. It has been characterised by Rietveld refinement of the X-ray powder diffraction pattern, DTA-TGA, infrared and Raman spectroscopies. Its structure is trigonal, R3̅m with cell parameters a=0.3061(4) nm and c=2.252 (3) nm. The decomposition of this hydrotalcite-like structure on heating up to 800 °C yields to a single phase spinel oxide. Besides, infrared and Raman spectroscopies showed the presence of spinel-like domains. The results of Rietveld refinement have revealed that this compound has the Fd3̅m space group (a=0.8088(4) nm), with crystallographic formula [Co(II)0.75Al0.25](8a)[Co(II)0.252Co(III)0.77Al0.98](16d)O4, which is of the general formula Co1.77Al1.23O4. This structure is also validated by the charge distribution (CD) analysis.

[Cu(2)(HF(2))(H(2)O)(8)][FeF(6)]·2H(2)O.

The title compound, octaaqua-(hydrogenfluorido)dicopper(II) hexa-fluoridoferrate(III) dihydrate, was synthesized under hydro-thermal conditions. The Cu atom is coordinated by one F and five O atoms within a highly distorted octa-hedron, forming dimeric [Cu(2)(H(2)O)(8)HF(2)](3+) units by edge sharing. These units are hydrogen bonded to [FeF(6)](3-) anions and to an inter-stitial water mol-ecule. The former feature Fe(3+) on a special position (). The dimeric copper units are linked to adjacent dimers by F-H⋯F hydrogen bonds. Additional O-H⋯O and O-H⋯F hydrogen bonds help to consolidate the crystal packing.

Sr(5)(VOF(5))(3)F(H(2)O)(3) refined from a non-merohedrally twinned crystal.

The title compound, penta-strontium tris-[penta-fluorido-oxido-vanadate(IV)] fluoride trihydrate, was obtained under hydro-thermal conditions. Its crystal structure has been refined from intensity data of a non-merohedrally twinned crystal. Two domains in almost equal proportions are related by a -180° rotation along the reciprocal [101]* vector. The structure may be considered as a derivative of the fluorite structure type, adopted here by SrF(2). In the title compound, fluorite-like large rods are recognized, built up from a group of 16 Sr atoms of which 6 are substituted by V atoms, leading to [Sr(10)V(6)](∞) units. These rods extend infinitely along the b axis and are inter-connected by the three water mol-ecules. Each of the water mol-ecules is shared by two different Sr atoms belonging to two different rods. The rods are also inter-connected by an 'independent' F atom in a distorted triangular [FSr(3)] coordination and by hydrogen-bonding inter-actions via donor water mol-ecules. The acceptors are either F atoms or the O atoms of the vanadyl ion, VO(2+), that is part of the [VOF(5)] isolated octa-hedron.