Rebuttal of the Existence of Solid Rare Earth Bicarbonates and the Crystal Structure of Holmium Nitrate Pentahydrate

Abstract

The synthesis routes of Gd(HCO3)3·5H2O and Ho(HCO3)3·6H2O, which are the only known bicarbonates of rare earth metals, were refuted and the published crystal structures were discussed. Because of the structural relationship of Ho(HCO3)3·6H2O to rare earth nitrate hexahydrates,[1] the synthesis of holmium nitrate hydrate was considered and the crystal structure of Ho(NO3)3·5H2O was solved by single crystal X-ray diffraction measurements. Ho(NO3)3·5H2O was determined to crystallize in the triclinic space group P1 (no. 2) with a = 6.5680(14) A, b = 9.503(2) A, c = 10.462(2) A, α = 63.739(14)°, β = 94.042(2)° and γ = 76.000(16)°. The crystal structure consists of isolated [Ho(H2O)4(NO3)3] polyhedra and non-coordinating water molecules. It is isotypic to other rare earth nitrate pentahydrates.