Lutetium carbonates

The solubility of rare earth carbonates is fairly low and ranges from 10 to 10 mol L . Rare earth carbonates can be obtained by the addition of ammonium carbonate to a solution of a rare earth water-soluble salt. In this case, the precipitates will all be hydrates. Lanthanum to neodymium carbonates contain eight water molecules while neodymium to lutetium carbonates contain two water molecules only. Rare earth carbonates can be dissolved in alkali metal carbonate solutions and form a double salt of alkali metals. 

The only example of this coordination number which is known at the present time occurs in the compound [Li(C4H80)4][Lu(CgH9)4] (Cotton et al., 1972). (The anion is the tetrakis(2,6-dimethylphenyl)lutetate(III) anion.) The structure of this compound is given in fig. 25.2 and shows that the lutetium-carbon bonds... 

Lutetium oxide (Lu O ), the oxide found in monazite ore, is a white solid. It is hygroscopic and also absorbs carbon dioxide, making it useful to remove CO in closed atmospheres. 

In aqueous media lutetium occurs as tripositive Lu3+ ion. All its compounds are in +3 valence state. Aqueous solutions of all its salts are colorless, while in dry form they are white crystalline solids. The soluble salts such as chloride, bromide, iodide, nitrate, sulfate and acetate form hydrates upon crystallization. The oxide, hydroxide, fluoride, carbonate, phosphate, and oxalate of the metal are insoluble in water. The metal dissolves in acids forming the corresponding salts upon evaporation of the solution and crystallization. 

The same group also showed that mono(cyclopentadienyl) mixed hydride/ aryloxide dimer complexes of several lanthanide elements (Y, Dy, Lu) could be synthesized easily by the acid-base reaction between the mixed hydride/alkyl complexes and an aryl alcohol [144]. These complexes reacted with C02 to generate mixed formate/carboxylate derivatives, which were moderately active initiators for the copolymerization of C02 and cyclohexene oxide, without requiring a co-catalyst. The lutetium derivative 21 was the most active (at 110°C, TOF = 9.4 h ), yet despite a good selectivity (99% carbonate linkages), the molecular weight distribution remained broad (6.15) (Table 6). 

Organolanthanide compounds display a remarkable chemistry with the simplest carbonyl derivative, namely carbon monoxide [280-287]. Organolanthanide activation of carbon monoxide was first observed by employing the monomeric alkyl complex Cp2 Lu(f Bu)(TH F) (Scheme 37) [281a]. Reaction of one equivalent CO yielded single insertion of CO into the Ln-fBu bond to form a r 2-acyl complex. However, excess CO yielded a multiple insertion and coupling of four molecules of CO led to an enedione diolate moiety which bridges two lutetium atoms (Table 18). 

Roesky introduced bis(iminophosphorano)methanides to rare earth chemistry with a comprehensive study of trivalent rare earth bis(imino-phosphorano)methanide dichlorides by the synthesis of samarium (51), dysprosium (52), erbium (53), ytterbium (54), lutetium (55), and yttrium (56) derivatives.37 Complexes 51-56 were prepared from the corresponding anhydrous rare earth trichlorides and 7 in THF and 51 and 56 were further derivatised with two equivalents of potassium diphenylamide to produce 57 and 58, respectively.37 Additionally, treatment of 51, 53, and 56 with two equivalents of sodium cyclopentadienyl resulted in the formation of the bis(cyclopentadienly) derivatives 59-61.38 In 51-61 a metal-methanide bond was observed in the solid state, and for 56 this was shown to persist in solution by 13C NMR spectroscopy (8Ch 17.6 ppm, JYc = 3.6 2/py = 89.1 Hz). However, for 61 the NMR data suggested the yttrium-carbon bond was lost in solution. DFT calculations supported the presence of an yttrium-methanide contact in 56 with a calculated shared electron number (SEN) of 0.40 for the yttrium-carbon bond in a monomeric gas phase model of 56 for comparison, the yttrium-nitrogen bond SEN was calculated to be 0.41. 

The product isolated from the reaction of a 1 1 stoichiometric amount of CO with the lutetium complex was characterized as a monoinsertion product, an acyl. From spectroscopic data, a dihaptoacyl structure involving significant Lu-0 interaction was postulated. With excess CO, a dimeric complex was isolated in which four CO molecules were coupled via one C=C double bond and two C—C single bonds to form an enedionediolate moiety. The condensation of these four CO molecules can be rationalized based on the carbenoid character of the dihaptoacyl carbon atom. This multiple coupling of CO has precedent in early transition metal... 

When rare earth oxides, hydroxides, or carbonates react with dilute sulfuric acid, rare earth sulfate hydrates are obtained and they have the formula RE2(S04)3 H20 where = 3,4,5, 6,8, and 9. The most common is = 9 for lanthanum and cerium and = 8 for praseodymium to lutetium and yttrium. Anhydrous compounds may be obtained by heating the respective rare earth sulfate hydrate at 155-260 °C, however, they easily absorb water to become hydrated again. 

Erbium and lutetium oxalates [81] decomposed after long induction periods required for complete dehydration. The carbonates which then formed were unstable and dissociated to yield oxides. The extents of carbon monoxide disproportionation during breakdown of these reactants were smaller (17% for Er and 6% for Lu). 

Watson et al. reported a leading example of (3-carbon elimination observed with a well-defined metal complex [67]. Thermal decomposition of a lutetium-isobutyl complex having a vacant coordination site leads to the formation of a lutetium-methyl complex and propene by way of (3-methyl elimination, the microscopic reverse of olefin insertion. A concerted four-center transition state is proposed. This study demonstrated that (3-carbon elimination is an energetically accessible process, and provided a model for the chain transfer that occurs during propene oligomerization. 

Scheme 18. Single and multiple carbon monoxide insertion into a lutetium alkyl bond...

The lutetium hahdes (except the fluoride), together with the nitrates, perchlorates, and acetates, are soluble in water. The hydroxide oxide, carbonate, oxalate, and phosphate compotmds are insoluble. Lutetium compounds are all colorless in the solid state and in solution. Due to its closed electronic configuration (4f " ), lutetium has no absorption bands and does not emit radiation. For these reasons it does not have any magnetic or optical importance, see also Cerium Dysprosium Erbium Europium Gadolinium Holmium Lanthanum Neodymium Praseodymium Promethium Samarium Terbium Ytterbium. 

Here, the so-called heavy lanthanides include the elements from samarium to-lutetium, except for ytterbium and europium which behave like bivalent metals and have unique properties. For these heavy-lanthanide-carbon systems, no complete phase diagram was found, only some information about the formation and the crystal structure of the carbides is available. On the basis of these data the general characteristics of the phase diagrams of the heavy-rare-earth-carbon systems can be summarized. In this case the yttrium-carbon phase diagram may be regarded as the best prototype available for compounds of the heavy lanthanide systems with carbon. 

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