Lanthanoid Nitrate Complexes with Some Polyethylene Glycols and Glymes

Lanthanoid nitrates (Ln(NO3)3) formed solid complexes with several polyethylene glycols and glymes. The compositions of the complexes were 1:1 (Ln:ligand) for triethylene glycol(EO3), tetraethylene glycol(EO4), pentaethylene glycol(EO5), and tetraglyme, 1:2 (Ln:ligand) for diethylene glycol, 2:1 for heptaethylene glycol, and 4:3 for pentaglyme and hexaglyme. Solid complexes were deposited also for hexaethylene glycol, but their compositions were not definitely determined. The solid complexes obtained here were all deliquescent. The deposition of the complexes was generally interfered with by water in the solution, and was not observed for some heavier lanthanoids when a small amount of water was present in the solution. The solubilities of the solid complexes with EO4 and EO5 increased with an increase in the atomic number of the lanthanoid, a fact suggesting a unique selectivity of the glycols. The infrared absorption bands of polyethylene glycols or glymes in the 1000–1150 cm−1 region became sharper upon the complexing of the glycols or glymes with lanthanoids; this sharpening can be explained by the change in the conformations in the ligand molecules.