Results of investigation rare-earth elements solvation on example neodymium (III) in water and in ethylacetate a given. Showed that replacement of water to ethylacetate is accompanied by reconstraction of neodymium ion coordination sphere. Conducted calculation of interatomic distances indicated to increase of a covalence part of link Nd (III) - O in organic solvent of ion polar. At addition in a solution of rare-earth elements salt 2,2′-dipiridyl complex connections of structure Ln(III): 2,2′-Dip, where Ln # La, Nd, Sm, Eu, Gd, Tb, Ho, Er, Yb and Lu a generated. Stability of complexes at therious temperature is appreciated. In change of thermodynamic characteristics of complexing process it is observed secondary periodicity, conducts of compensating effect a shown.