ᐊ P7-15
Open Readings 2021 • P7-16
P7-18 ᐅ

SYNTHESIS AND CRYSTAL STRUCTURES OF SAMARIUM(III)–CONTAINING HETEROPOLY SALTS WITH PEACOCK–WEAKLEY TYPE ANION Na9–xHx[Sm(W5O18)2]·nH2O

Oleksandra Mariichak1, 2, Georgii Rozantsev1, Serhii Radio2

1 Faculty of Chemistry, Biology and Biotechnologies; Vasyl' Stus Donetsk National University, Ukraine

2 Department for Research, Research Laboratory “Chemistry of Polyoxometalates and Complex Oxide Systems”, Vasyl' Stus Donetsk National University, Ukraine

[email protected]

To determine the critical acidity for obtaining of lanthanide(III)-containing heteropoly salts with Peacock-Weakley type anion [Ln(W5O18)2] (Ln= lanthanide) a new procedure for the synthesis of sodium heteropoly decatungstosamarates(III) from Sm(NO3)3 – Na2WO4 – HNO3 – H2O solutions with the ratio v(Sm) : v(W) = 1:10, which acidified up to Z = v(HNO3)/v(Na2WO4) = 0.90–1.20 (Mariichak O.Yu., et al. Patent of Ukraine No. 121322, 2017), was used. The formation of heteropoly anions by self-assembly process corresponds to the equation:

$$Sm^{3+} + 10 WO_{4}^{2-} + (8+x) H^{+} = H_{x}[Sm(W_{5}O_{18})_{2}]^{(9-x)-} + 4 H_{2}O.$$

The synthesized crystalline salts of Na8H[Sm(W5O18)2]·38.25H2O (Z = 0.90) and Na7H2[Sm(W5O18)2]·24.75H2O (Z = 1.00) were characterized by Single Crystal X-ray analysis (Fig. 1), FT-IR spectroscopy and elemental analysis.

The main crystallographic data for Na8H[Sm(W5O18)2]·38.25H2O are: triclinic, P−1, a = 12.894(4) Å, b = 13.112(4) Å, c = 20.885(6) Å, α = 76.99(3)°, β = 84.05(3)°, γ = 77.42(3)°, V = 3352.2(18) Å3, Z = 2; and for Na7H2[Sm(W5O18)2]·24.75H2O are: triclinic, P−1, a = 12.5506(4) Å, b = 12.9656(2) Å, c = 18.9744(8) Å, α = 96.461(2)°, β= 100.389(3)°, γ = 102.472(2)°, V = 2928.23(17) Å3, Z = 2.

Figure 1
Fig. 1. Crystal structures of Na8H[Sm(W5O18)2]·38.25H2O (a), and Na7H2[Sm(W5O18)2]·24.75H2O (b).

Amorphous precipitates which isolated from solutions with Z = 1.10 and 1.20, were investigated by FT-IR spectroscopy. The results of the study showed the presence of Peacock-Weakley type anion in the salt obtained at Z = 1.10, and heptatungstate anion [W7O24]6– – at Z = 1.20. Thus, Z = 1.10 is the critical acidity, which allows to obtain salts with heteropoly decatungstosamarate(III) anion.

The obtained X-ray diffraction data supplement the results of structural studies of two Sm(III)-containing polyoxotungstates with Peacock-Weakley type anion described in the literature: Na6H3[Sm(W5O18)2]·28H2O [1] and K3Na4H2[Sm(W5O18)2]·22H2O [2]. From the analysis of the comparison of structural parameters of compounds it can be concluded that changes in the composition of the cationic sublattice and the presence of different numbers of coordinated and uncoordinated water molecules have almost no effect on the values of bond lengths and valence angles in the heteropoly anion.

Acknowledgments: The study was carried out within the Fundamental Research Programme funded by the Ministry of Education and Science of Ukraine (grants ID 0119U100025, 0120U102059).

[1] T. Ozeki, T. Yamase, Hexasodium Trihydrogen Decatungstosamarate Octacosahydrate, Acta Cryst. C50, 327–330 (1994).

[2] T. Ozeki, T. Yamase, Effect of lanthanide contraction on the structures of the decatungstolanthanoate anions in K3Na4H2[LnW10O36]·nH2O (Ln= Pr, Nd, Sm, Gd, Tb, Dy) crystals, Acta Cryst. B50, 128-134 (1994).