The synthesis and properties of lanthanide complexes with different neutral ligands

Abstract

Listen

Translate article

The present paper reports the synthesis of new coordination complexes of lanthanide nitrates and chlorides with mono- and bidentate ligands. Dihexylsulfoxides (DHSO), tributylphosphate (TBP), aminosulfides, aminosulfoxides of various structures, and the sulfoxides of oil origin have been used as ligands. The structures and some physical chemistry properties of chloride and nitrate lanthanide complexes with the sulfoxides of oil origin are presented. The complex compound structures have been shown to depend upon the process of producing and to correspond to the formula LnA 3·mHCO·NH 2O, where LNCe, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, Lu, m = 3-5, n = 0-3. All the IR spectra of the isolated compounds have shown a 10–60 cm -1 band shift of sulfoxide group stretching vibrations towards the low frequency region as compared with that band position of a free sulfoxide. These data evidence the formation of electron donor-acceptor bonding of the central ion through the sulfoxide oxygen. Conductivity and molecular mass measurements of the synthesized complexes verify that the acido ligand is included in the internal sphere of the complex. Investigations of IR and electron absorption spectra of the nonhydrated nitrate and chloride lanthanide complexes with oil sulfoxides have shown the relative stability of electron donor-acceptor bonding in metal sulfoxide of the lanthanide series to grow with the increasing effective charge of hydration of the central ion the lower is the hydration value, which is dropping with increasing metal cation effective charge. This paper presents the structures and some physical chemistry properties of the lanthanide chloride and nitrate complexes with different ligands, those, complexes possessing internal and external spheres and being based upon dihexylsulfoxide and tributyl phosphate. In hydrocarbon solutions the internal sphere different ligand complexes have been found to undergo the process of disproportionation of the following type. ▪ Lanthanide nitrate complexes with aminosulfoxides and aminosulfides have been synthesized and investigated, the structures and some physical chemistry properties of the obtained complexes given. Complexing of the lanthanide nitrates with aminosulfides has revealed the central atom bonding with aminosulfides to proceed through a tertiary nitrogen. The complex formation of the lanthanide nitrates with aminosulfoxides has been supposed to form a chelate structure, for an aminosulfoxide molecule possesses two active groups - NC and SO. However, the obtained data have evidenced the coordination of the central atom in the complexes to proceed through the sulfoxide group oxygen only, and the tertiary nitrogen not to participate in the formation of the electron donor-acceptor bonding with metal ions. Further investigations of the pattern complexes of cobalt nitrates with aminosulfides and aminosulfoxides have shown that steric factors are, probably, the main barrier which prevents the tertiary nitrogen atom from the participation in the formation of electron donor-acceptor bonding with the central atom. Dipole moments of the complexes synthesized have been measured and their thermal stabilities have been studied by the thermogravimetric technique. The thermal investigations have revealed the decomposition of the complexes not to depend on the metal nature, and the ligand nature to influence the thermal stabilities of the complexes. As a rule, complexes are more stable than ligands, for the decomposition temperatures of the former are 20–30°C higher than those of the latter.