Cerium chloride anhydrous

Cement, laboratory, 189 Cerium amalgam, 15 Cesium, metallic, 79 Chloroamine, 59 Chlorides, anhydrous, 28, 29 of silicon, 42 Chloroplumbic acid, 48 Chromi-oxalates, 37 Chromous acetate, 122 Chromous chloride, 124, 125 solution, 124 tetrahydrate, 126 trihydrate, 126 Cinnabar, 20 Cobalti-oxalates, 37... 

Magnesium cerium(III) nitrate, 3Mg(N03)2-2Ce(N03)3-24H20, separation of praseodymium from lanthanum by, 2 57 Magnesium chloride, anhydrous, 1 29 5 154n. 6 9 Magnesium cyclopentadienide, 6 11 Magnesium rare earth nitrates,... 

Reaction of anhydrous cerium(iii) chloride with RLi reagents affords organocerium compounds The cerium chloride is prepared by heating CeCl3(H20)7 in vacuo up to 140 °C and is in fact a monohydrate [CeCl3(H20)], see W.J. Evans, J.D. Feldman, and J.W. Ziller, J. Am. Chem. Soc., 1996,118,4581. Reaction is carried out at -78 °C, as decomposition is rapid at 0 °C, especially if a /3-hydrogen is present in the R group. The exact nature of the cerium species is uncertain. 

A mixture of LiAlHi and CeCls is a powerful reducing agent, reducing unsaturated carbonyl compounds to allylie alcohols (in this case, anhydrous cerium chloride is a necessity). It will reduce phosphine oxides to phosphines, oximes to primary amines, and o ,jS-unsaturated carbonyl compounds to allylie alcohols. In particular, it reduces both aryl and alkyl halides to hydrocarbons. 

General procedure for the preparation of anhydrous cerium chloride... 

Organocerium reagents are prepared in situ by the reaction of organolithium compounds with anhydrous cerium chloride or ceriiun iodide, as shown in equation (1). A variety of organolithium compounds can be employed, including alkyl-, allyl-, alkenyl- and alkynyl-lithiums, which are all converted to the corresponding cerium reagents. 

The following procedure is recommended for the small-scale preparatiai of anhydrous cerium chloride. Cerium chloride heptahydrate (ca. 20 g) is placed in a round-bottomed flask connected to a dry ice trap. The flask is evacuated and heated to lOO C for 2 h. The resulting opaque solid is quickly pulverized in a mortar and is heated again, in vacuo at the same temperature, for 2 h with intermittent shaking. A stirrer is then placed in the flask, which is subsequently evacuated, and the bath temperature is raised to 135-140 C. Drying is complete after 2-3 h of stirring. 

Anhydrous cerium chloride can be stored for long periods provided it is strictly protected from moisture. Cerium chloride is extremely hygroscopic hence, it is recommended that it be dried in vacuo at ca. 140 C for 1-2 h before use. 

Cerium enolates are generated by the reaction of lithium enolates with anhydrous cerium chloride in THF. The cerium enolates react readily with various aldehydes and ketones at -78 °C (Scheme 24). The yields are generally higher than in reactions of lithium enolates. This is presumably due tt> the relative stabilities of the adducts, that of the cerium reagent being greater by virtue of coordination to the more oxo lic cerium atom. The stereochemistry of the products is almost the same as in the case of lithium enolates, as shown in Table 4. The reaction is assiuned to proceed through a six-membeied chair-like transition state, as with lithium enolates. 

It was Carl Gustaf Mosander (Figure 17.8), from 1836 Berzelius successor as professor of chemistry, who started the great work of separating the almost inseparable. As Berzehus student from 1820 he soon came into his service. He prepared cerium sulfide and let it react with chlorine. Anhydrous cerium chloride CeClj, was formed, from which he prepared metalHc cerium by reduction with potassium metal. This was in about 1825. With all his work with different cerium compounds he began to... 

J. G. Gahn in Sweden and N.-L. Vauquelin in France tried in vain to obtain metallic cerium. C. G. Mosander prepared anhydrous cerous chloride and subjected it for a long time to the action of potassium vapor. After washing the residue with cold alcohol, he obtained a brown powder which,... 

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