Ytterbium selenates

The measurements of Serebrennikov, Batyreva, and Tsybukova [81SER/BAT], which established the phase diagram of the system Yb2(Se04)3-Nd2(Se04)3-H20 at 298.15 K, indicate that Yb2(Se04)3-8H20 is the stable ytterbium selenate in contact with water. The reported solubility  

No other thermodynamic data of ytterbium selenates have been found. 

Data for Yb2(Se04)3 and additional data for Yb2(Se04)3-nH20 are found in Section 29.4.1 and 29.4.2, on pp. 453 and 454, respectively. 

Nearly transparent tabular crystals of Yb2(Se04)3-8 H2O are obtained when Yb203 is treated with Se02 in H2O, heated with H2O2 for 12 h in a water bath, and concentrated by slow evaporation, Neogy, Nandi [2, 5]. For the existence in the system Yb2(Se04)3-Nd2(Se04)3-H20 at 25°C, see p. 479. 

The crystals are monoclinic, isostructural with Yb2(S04)3-8H20, space group C2/c-C h (No. 15) with a = 13.704(6), b = 6.831 (3), c = 18.507(7) A and p = 101.90(31)° (calculated density = 3.60 g/cm for Z = 4), as shown by X-ray single crystal studies. The structure was determined by comparison to the sulfate and refined by full-matrix least-squares calculations to an R of 0.041. Using anisotropic thermal parameters, the atomic coordinates are as follows  

Compared with the sulfate, the larger selenate ion does not cause any significant distortion in the coordination geometry around Yb. The Yb polyhedron is intermediate between a square antiprism and a dodecahedron. The Yb-0(Se04) distances vary from 2.236(8) to 2.385(7) A, Yb-0(H20) from 2.278(8) to 2.462(8) A. The Se(1) and (2)-0 distances are 1.620(7) to 1.657(7) and 1.612(9) to 1.636(8) A, respectively. Bond angles are also given, Hiltunen, Niinisto [1]. 

The magnetic anisotropy was measured in three directions with b and c axes vertical and with (100) plane horizontal. The principal anisotropies (X1-X2) and (X3-X2) and the principal magnetic susceptibility Xi, corrected for diamagnetism (all in 10 cm /g-atom), are given in the following table together with the effective magnetic moment Heff in xq  

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Rubidium Holmium Selenates. Rubidium Ytterbium Selenates... 

By analogy with the sulfate studies (see section 4.4.3), magnetic studies have also been carried out. Neogy and Nandi (1982) concluded that the crystal field around Yb " in the structure of ytterbium selenate octahydrate is of tetragonal symmetry at least to the first approximation. However, the authors did not compare their model with the actual crystal structure of the ytterbium compound described in the literature (table 15). In a later study, the magnetic behavior of Dy " was studied and the effects of J-J mixing were noted (Neogy and Nandi, 1983). 

Diazo transfer to 1 followed by irradiation in the presence of bis-(trimethylsilyl)amide led to ring contraction with concomitant carbonyl extrusion, to give 7. Dehydration to the nitrile followed selenation then set the stage for a highly diastereoselective ytterbium-catalyzed Diels-Alder reaction, to give, after reduction and protection, the pentacyclic intermediate 2. 

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