Thermodynamics and structure of thiocyanato complexes of yttrium(III) and lanthanide(III) ions in N,N-dimethylformamide

Abstract

The formation of thiocyanato complexes of yttrium(ii1) and lanthanide(iii) (Ln = La, Nd, Tb, Ho, Tm, Yb) ions has been studied by calorimetry in N,N-dimethylformamide (DMF) containing 0.2 rnol dm-3 (C2H,),NCI0, as a constant ionic medium at 25°C. The data were well explained in terms of formation of a series of mononuclear [Ln(NCS),](3-")+ (n = 1-3) complexes, and their formation constants, reaction enthalpies and entropies were determined. ''Y NMR and Raman spectra suggest that the metal ions form inner-sphere complexes with thiocyanate ions in DMF. Furthermore, with Yb"' and Ln"', the Raman band for the CS stretching vibration of SCNshows an abnormal shift and broadening. Although less marked, the same effect was observed with La"', Ce"' and Tm"'. This was explained in terms of establishment of a solvation equilibrium with the [Ln(NCS)l2+ complex, i.e. the complex consists of two distinct species which differ in the number of coordinating solvent molecules.

Soluble Yttrium Chalcogenides: Syntheses, Structures, and NMR Properties of Y[η3-N(SPPh2)2]3 and Y[η2-N(SePPh2)2]2[η3-N(SePPh2)2]

“…1 NMR Studies. With the general lack of solution studies of soluble rare-earth chalcogenide compounds, [32][33][34][35][36][37] the present compounds are attractive for NMR spectroscopic study because they contain, among others, 31 P, 89 Y, and 77 Se (for 2) active nuclei. These data are summarized in Table 3.…”

Solvation structure of lanthanide(iii) ions in solvent mixtures of N,N-dimethylformamide and N,N-dimethylacetamide studied by titration Raman spectroscopyElectronic supplementary information (ESI) available: Crystallographic data (single crystal, [Gd(DMF)4(DMA)4](ClO4)3), (CCDC reference number 185878). See http://www.rsc.org/suppdata/cp/b2/b204162f/

“…We have so far studied the thermodynamics of complexation and the structure of a series of lanthanide(III) ions in N,Ndimethylformamide (DMF), N,N-dimethylacetamide (DMA) and their mixtures from the viewpoint of the solvation steric effect. [1][2][3][4][5] Although both solvents have similar electron-pair donating and accepting abilities; i.e. the donor number D N is 26.6 and 27.8, and the accepter number A N is 16.0 and 13.6 for DMF and DMA, respectively, the lanthanide(III) ion shows quite different complexation behavior in these solvents due to the solvation steric effect of DMA.…”