Layered nickel–cobalt hydroxyacetates and hydroxycarbonates: Chimie douce synthesis and structural features

Layered nickel–cobalt hydroxyacetates Ni1−xCox(OH)2−y(OAc)y·nH2O were first prepared by hydrolysis in polyol medium and then layered nickel–cobalt hydroxycarbonates were obtained by solid/liquid exchange reaction starting from hydroxyacetates homologues. The interlamellar distances and the characteristics of IR absorption band of anions for low cobalt content hydroxyacetates (x≤0.25) are different from those with a higher cobalt amount. Such a difference is not observed for carbonate compounds. Despite these different features, UV analysis shows that cobalt (II) ions are present both in octahedral and tetrahedral sites for all acetate and carbonate compounds. The amount of cobalt in Td sites, inferred from magnetization measurements, increases up to 26–27% when the total amount of cobalt increases. Two structural models closely related to the hydrozincite one are proposed for the solid solutions. These models differ by the organization of anionic species and water molecules between the layers.