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Lanthanide(III) trifluoromethanesulfonate complexes in anhydrous acetonitrile

1993; Elsevier BV; Volume: 207; Issue: 1 Linguagem: Inglês

10.1016/s0020-1693(00)91459-2

1873-3255

Plinio Dí Bernardo, Gregory R. Choppin, Roberto Portanova, Pier Luigi Zanonato,

Analytical Chemistry and Sensors

Anhydrous solutions of lanthanide(III) trifluoromethanesulfonates (triflates) in acetonitrile have been prepared and studied. Solubility measurements revealed that among the salts considered (Ln(SO3CF3)3; LnLaLu) only the heavier ones (LnDyLu) are soluble (S>150 mmol dm−3) in strictly anhydrous conditions. Additions of small quantities of water proved that the solubility of lighter salts depends strongly on the presence of this reagent in solution. The ability of the triflate ion to coordinate the tervalent lanthanides in anhydrous solutions has been investigated by means of conductometric and FT-IR techniques. Quantitative IR measurements allowed detection of the main species in solution to be Ln(SO3CF3)2+ and Ln(SO3CF3)3. Their apparent equilibrium constants are reported. The competition of perchlorate and triflate for the Ln(SO3CF3)2+ ion has also been studied. Measurements of the formation constant of the mixed complex, Ln(SO3CF3)2ClO4, suggested that the affinity of the perchlorate ion for the Ln(SO3CF3)2+ complex is about ten times lower than that of the third triflate. The effects of added water or dimethyl sulfoxide on the dissociation of the triflate complexes in AN were also obtained.