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

The synthesis routes of Gd(HCO 3 ) 3 · 5H 2 O and Ho(HCO 3 ) 3 · 6H 2 O, 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(HCO 3 ) 3 · 6H 2 O to rare earth nitrate hexahydrates,[1][M. S. Wickleder, 2002] the synthesis of holmium nitrate hydrate was considered and the crystal structure of Ho(NO 3 ) 3 · 5H 2 O was solved by single crystal X‐ray diffraction measurements. Ho(NO 3 ) 3 · 5H 2 O was determined to crystallize in the triclinic space group P 1 (no. 2) with a = 6.5680(14) Å, b = 9.503(2) Å, c = 10.462(2) Å, α = 63.739(14)°, β = 94.042(2)° and γ = 76.000(16)°. The crystal structure consists of isolated [Ho(H 2 O) 4 (NO 3 ) 3 ] polyhedra and non‐coordinating water molecules. It is isotypic to other rare earth nitrate pentahydrates.