Lanthanide carbonate

Compounds containing lanthanide-carbon o-bonds have recently been reviewed. ... 

Early mechanistic studies concerning organolanthanide-catalyzed olefin polymerization reactions showed that insertion of the unsaturated hydrocarbon into the lanthanide-carbon cr-bond is a key step. It was first demonstrated for the... 

The lanthanide triflates may also be obtained by the addition of triflic acid to lanthanide carbonates in ethanol or acetonitrile [18]. Filtration and concentration of the filtrate yield a solid salt which is washed with solvent. Lanthanide salts of poorly coordinating anions such as PFg, BF4 or BiCftHs) have been also used in the synthesis of lanthanide complexes as starting materials. Adducts of acetonitrile with europium tetrafluoroborate (BF4) and hexafluorophosphate (PF ) have been prepared [19]... 

The complexes may also be prepared by the addition of a solution of carboxylic ligand to an equivalent amount of (i) a lanthanide carbonate [28], (ii) hydroxide [29] or (iii) oxide [30] with a slight excess of the latter. The insoluble part is filtered and the filtrate evaporated to obtain crystalline complex. Anhydrous lanthanide complexes of small chain carboxylic acids may be prepared by (i) the dissolution of lanthanide carbonate in excess of the carboxylic acid, followed by heating to obtain complete dissolution of the suspension and partial evaporation of the solution to obtain the crystals [31], (ii) anhydrous lanthanide is converted into the corresponding monochloroacetate by the addition of an excess of monochloroacetic acid, followed by heating under reflux at reduced pressure for 2 h. Then ether is added to precipitate the salt [32], (iii) the addition of dimethyl formamide and benzene to lanthanide acetates and distillation of the water azeotropes to obtain anhydrous complexes. The last procedure yielded lighter lanthanide complexes solvated with dimethyl formamide [33], The DMF may be removed by heating in a vacuum at 120°C. 

Cerium(III) is considered to be a representative element for trivalent lanthanides and carbonate ions. Lanthanide carbonates are insoluble and the experimental data for the formation constants of the various carbonato species are available for Ce(III)-CC>3 system [148],... 

The synthesis, structure, and physical and chemical properties of organo-lanthanide complexes containing only polyhaptocyclopentadienyl and cyclooctatetraenyl metal-carbon bonds are fully covered in other reviews (5-7). This section will focus on lanthanide-carbon single bonded species only. Ln—C single bonds are found almost exclusively in only two types of complexes homoleptic complexes, and heteroleptic... 

From Cantrell (1988), estimated from correlations of lanthanide ionic radii (Shannon, 1976) versus lanthanide carbonate complexation constants, plus the actinide ionic radius estimates of Shannon (1976). 

Tsutsui and Ely have extended the general method for preparing a-bonded actinide complexes to the synthesis of compounds containing lanthanide-carbon a-bonds (37,38,39). Using the reaction shown in eq.3, they synthesized a number of alkyl, aryl, and alkynyl derivatives. The metals chosen vary from Gd to Yb. Like their uranium analogs, they are oxygen and moisture sensitive, but they are surprisingly thermally stable. 

S.A. Cotton (1997) Coordination Chemistry Reviews, vol. 160, p. 93 - Aspects of the lanthanide-carbon cr-bond . 

Some crystallochemical characteristics of complex iridium sulphamates have been reported152. A series of lanthanide sulphamates (122) have been prepared153, by reaction of the lanthanide carbonate and sulphamic acid, isolated as solids and examined by infrared, X-ray diffraction and thermography. The sulphamates have a higher solubility in water than other alkali or alkaline earth sulphamates. 

General characteristics of phase diagrams of the light-lanthanide-carbon systems 67... 

Except for the phase diagram of the lanthanum-carbon system, no complete phase diagram is available for the light-lanthanide-carbon systems. Only some data on the formation of the carbides have been reported. However, on the basis of these data, the general characteristics of the binary light-lanthanide-carbon phase diagram can be deduced. 

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. 

Summarizing the phase relationship in the heavy-lanthanide-carbon systems and the general characteristics with respect to formation of the carbides, it can be concluded that the phase diagram of the yttrium-carbon system is a good prototype of the heavy-lanthanide-carbon systems, which have not yet been studied in detail. In addition, on the basis of the yttrium-carbon phase diagram the unknown information about the R C phase diagrams could be deduced. 

Many investigators have studied the phase relationship and the formation of the carbides in both the Eu-C and the Yb-C systems, but no complete phase diagram was reported although some data are available on carbides that are formed in the systems. Although europium and ytterbium exhibit variable-valence tendencies, the properties and lattice parameters of their carbides do not follow the systematic variation encountered between the individual lanthanide-carbon system. In addition, an additional new phase, RCs (R = Eu and Yb) forms in the two systems, which is reported to be hexagonal with a Pbj/mmc space group (Guerard and Herold 1975, El-Makrini et al. 1980). 

In comparison with the carbide-forming characteristics of the other heavy-lanthanide-carbon systems, the europium-carbon and ytterbium-carbon systems behave like their neighboring systems. In particular, the types and structures of these carbides are identical. The main difference is the larger lattice parameter of the... 

The formation of the rare-earth-nitrogen-carbon compounds has been investigated only for the light lanthanide systems with the emphasis on the existence of the monocarbide of La, Ce, Pr and Nd, in the presence of nitrogen. It is well known that no evidence for the existence of a face-centered cubic phase, assumed to be the monocarbide, was found in the detailed work on the light-lanthanide-carbon systems (Spedding et al. 1958, Dancy et al. 1962, Anderson et al. 1969). 

Krikorian, N.H., T.C. Wallace and M.G. Bowman, 1967, Phase relationships of the high-carbon portion of lanthanide carbon system, in Proprieties Thermodynamiques Physiques ct Structurales des Derives Semi-Metalliqucs, Orsay, 28 Sept.-l Oct 1965 (Centre National Recherche Scientifique, Paris) p. 489. 

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