Ytterbium acetate

Lutetium, purification of, from lutetium ytterbium acetate solution with sodium amalgam, 5 36... 

Purification of Ytterbium and Lutetium. One hundred grams of crude lutetium-ytterbium acetate dissolved in 133 ml. of boiling water was treated with 22.7 g. of sodium in 250 ml. of mercury and with 7 ml. of glacial acetic acid. The resulting amalgam gave a yield of pure ytterbium oxide of 73%. Treatment of a similar sample with 28.4 g. of sodium gave a yield of pure ytterbium(III) oxide of 93%. 

Nugent TC, El-Shazly M, Wakchaure VN. Ytterbium acetate promoted asymmetric reductive amination significantly enhanced stereoselectivity. J. Org. Chem. 2008 73(4) 1297-1305. 

The latter reaction could be repeated ten times without loss of activity of Yb-XN-1010. Similar results were obtained with ytterbium(III) loaded Amberlyst 15W resin in a two-step one-pot procedure first involving the formation of the active dimethyl acetal from a benzaldehyde derivative which was followed by in situ protection of sucrose (Scheme 4.17) [100]. 

There have been efforts to enhance stereoselectivity in radical polymerization by using fluoroalcohols or Lewis acids that complex with monomers such as MMA and vinyl acetate [Isobe et al., 2000, 2001a Okamoto et al., 2002], In almost all instances the effects are nil or very small. For example, the use of perfluoro-t-butyl alcohol as solvent instead of toluene changes (rr) from 0.89 to 0.91 in the polymerization of MMA at —78°C. An exception is in the polymerization of acrylamide in the presence of some rare-earth Lewis acids such as ytterbium triflate. The polymer is atactic at 0°C, (m) = 0.46, in the absence of the Lewis acid, but significantly isotactic, (m) — 0.80, in the presence of the Lewis acid. The reason for this effect is unclear. More highly isoselective polymerization occurs in some radical polymerizations of MMA (Sec. 8-14b). 

C,Hj, Acetic acid palladium complex, 26 208 tungsten complex, 26 224 02CiH(, 2-Propenoic acid, methyl ester platinum ester, 26 138 02C4Hu, Ethane, 1,2-dimethoxy-solvates of chromium, molybdenum, and tungsten carbonyl cyclopentadienyl complexes, 26 343 tungsten complex, 26 50 ytterbium complex, 26 22 02C4Hi, -NaCsHs, Ethane, 1,2-dimethoxy-compd with cyclopentadienylsodium(l l), 26 341... 

Readion of anisole (1) with acetic anhydride was chosen as a model, and ytterbium trifluoromethanesulfonate (ytterbium triflate, Yb(OTf)3) was the first RE(OTf)3 representative used. Several reaction conditions were examined the results are summarized in Table 1. When acetic anhydride, acetonitrile, or nitromethane was used as a solvent (entries 4—10), the reaction mixture became homogeneous and the acylation reaction proceeded smoothly. Nitromethane gave the highest yield of4-methoxyaceto-phenone (2) (entries 7-10). On the other hand, in carbon disulfide, dichloroethane, or nitrobenzene (entries 1-3), the reaction mixture was heterogeneous and the yield of 2 was low. It was noted that the acylation proceeded quantitatively when a catalytic amount of Yb(OTf)3 was used (0.2equiv., entry 9). Even when 0.05 equiv. of the catalyst was employed, 2 was obtained in 79 % yield (entry 10). 

Benzaldehyde (81 mg) and methyl trimethoxysilyl dimethylketene acetal (165 mg) were added to a mixure of 3 ml perfluorooctane and 4 ml toluene. To this mixture was added Imol % (based on benzaldehyde) ytterbium (tris(trisperfluorooctanesulfonyl)methide) and the reaction stirred 15 minutes at 40°C. Mixing and heating were stopped and the mixture separated into upper toluene layer and lower perfluorooctane layer. Each layer was analyzed by gas chromatography 99% of the product was detected in the lower layer. Atomic emission spectrometry indicated that at least 99% of the catalyst was also present in the lower layer. 

Acetals Various lanthanide chlorides are efficient catalysts for acetalization of aldehydes by methanol. Lanthanum chloride and cerium chloride are satisfactory for aliphatic aldehydes, but erbium chloride and ytterbium chloride are generally superior, particularly for aromatic and bicyclic aldehydes. Addition of trimethyl orthoformate as a water scavenger allows use of the commerically available hydrated forms of the salts. Acetals can be obtained in 80-100% yield from reactions conducted for 10 minutes at 25°. 

The reaction of yne-ones (also synthons for 1,3-dicarbonyl compounds) with 3-amino-enones or 3-amino-acrylates (the Bohlmann-Rahtz reaction) is regioselective, since conjugate addition of the ketone enamine is the first step the intermediates thus produced can be isolated from reactions in ethanol and converted on to the aromatic pyridine Acetic acid or ytterbium triflate give good results. 

Sodium amalgam extraction can thus be used to remove the whole of the samarium, europium, or ytterbium from mixtures with the other lanthanons. If the initial concentration of any of these is large, the efficiency of the reaction may exceed 75%. Low efficiencies characterize the removal of traces of these elements. Efficiency is enhanced by keeping the acetate solution as nearly free from sodium ion as possible and withdrawing much of the sodium amalgam before it can react. The extraction is an equilibrium process. 

Ytterbium and samarium acetates require at least 1.5 and 2.5 parts of water, respectively, for solution. 

If the acetate is rich in europium or ytterbium, the yellowish or greenish colors of the dipositive ions may develop in solution. Similarly, material rich in samarium may give a reddish-brown solution. With material poor in these elements, color development indicates sodium exhaustion and solution of the lanthanon amalgam. 

The crude lutetium acetate solution remaining was extracted with five successive portions of sodium amalgam, each consisting of 0.25 g. of sodium in 7 ml. of mercury. Sodium ion was eliminated through precipitation of the hydroxide and reconversion to acetate. Three more series of similar sodium amalgam extractions were made. Lutetium material recovered from the final aqueous solution was spectroscopically free from ytterbium. 

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