Compounds of the Lanthanides

Many of the binary compounds of the lanthanides, such as oxides, nitrides, and carbides, can exist as non stoichiometric compounds. These form crystals where some of the anions ate missing from the sites the anions normally occupy. 

Table 30.3 Oxidation states and stereochemistries of compounds of the lanthanides )...

The first weU-characterized organometallic compounds of the lanthanides or actinides were the tricyclopentadienides of various lanthanide ions S3mthesized by Birmingham and Wilkinson in 1954 (97—98). Anhydrous metal chlorides were reacted with sodium cyclopentadienide in tetrahydrofuran as follows ... 

Most transition metals of the three d-series in all their valency states exhibit ionic radii within the limits of 0.55 and 0.86 A, favourable to octahedral coordination. In fact higher coordination numbers are observed only in fluorides of the largest transition ions, above all in compounds of the lanthanide and actinide series. Therefore fluorides of those elements, though sometimes isostructural with compounds of the d-series, will not be discussed here. For information the books and reviews written by Spedding and Daane (291), Katz and Seaborg (181) and Kaiz and Sheft (182) may be consulted. 

The study of coordination compounds of the lanthanides dates in any practical sense from around 1950, the period when ion-exchange methods were successfully applied to the problem of the separation of the individual lanthanides,131-133 a problem which had existed since 1794 when J. Gadolin prepared mixed rare earths from gadolinite, a lanthanide iron beryllium silicate. Until 1950, separation of the pure lanthanides had depended on tedious and inefficient multiple crystallizations or precipitations, which effectively prevented research on the chemical properties of the individual elements through lack of availability. However, well before 1950, many principal features of lanthanide chemistry were clearly recognized, such as the predominant trivalent state with some examples of divalency and tetravalency, ready formation of hydrated ions and their oxy salts, formation of complex halides,134 and the line-like nature of lanthanide spectra.135... 

Magnetic properties (ot 300 K) of some compounds of the lanthanide metals0... 

Synthetic routes to compounds containing M-C o bonds are fairly obvious. Substitution of, e.g., Cl by CH, can be effected by treatment with LiCH3 or CH3MgBr. A number of reaction types mentioned in Chapter 9 - oxidative addition, reductive elimination, insertion and cyclometallation (Sections 9.6 and 9.7) - have their uses in preparative routes to M-C bonds. The formation of organo-compounds of the lanthanides and actinides is an area of growing interest. Preparative methods are similar to those for other ER species where E is of relatively low electronegativity, e.g. ... 

Organometallic Compounds of the Lanthanides, Actinides, and Early Transition Metals. (Edit. Cardin, D.J.). Chapman Hall London, 1985. 

This procedure was first used to prepare ruthenocene and other ruthenium complexes of cyclic olefin (136). The acyclic ruthenocenes are pale yellow, air-stable materials, soluble in organic solvents and readily sublimed. One representative compound of the lanthanides, NdPl 3 (137), and one of the actinides, UP1 3 (138), have also been described. 

LFT has been applied to the splitting of the 4f and 5f orbitals in compounds of the lanthanides and actinides respectively. This article deals only with applications to d-block chemistry. 

Mixed valency is not limited to consideration of individual ions in different oxidation states. Delocahzed systems also exist that exhibit properties of mixed valency, as in many organometalhc mixed valence compounds. For example, phthalocyanine, Pc (1), sandwich compounds of the lanthanides, Ln(Pc)2, are best described as containing the two Pc anionic ligands in mixed valent charge states of —2 and — 1 with the metal ion Ln +. 

Organometallic compounds of the lanthanides in the oxidation state Ln(II) were first reported in the early 1980s... 

A number of volatile rare earth chelates containing the ligands, l,l,l,2,2,3,3-heptafluoro-7,7-dimethyl-4,6-octanedi-one, [H(fod)], and 2,2,6,6-tetramethyl-3,5-heptanedione, [H(thd)] have been synthesized and investigated. The fod complexes are more volatile than other known compounds of the lanthanide elements. The fod complex of Sc(III) and the lanthanide thd compounds are anhydrous. The fod chelates of Y(III) and the lanthanides are isolated as hydrates but can easily be dehydrated in vacuo over P Oio. Gas chromatographic and thermo gravimetric data reveal that the volatilities of the complexes increase as the ionic radii of the metal ions become smaller. 

The second t)q)e of cluster compounds of the lanthanide alkoxides features one or several small-unit, inorganic ligands including oxo, hydroxo, halo, and other groups as part of the cluster core structure. Frequently, a combination of such ligands is foimd in the same cluster species. In a sense, this "central spherical charge density" drives the assembly of the polynuclear complexes without their participation, no clusters are formed or species of completely different structures result. 

I. The initial compound of the lanthanide can be obtained by reacting its halide with the corresponding organic base [5]. The research is usually carried out with complexes containing various electron donor ligands, L, such as alcohols [6, 7], cyclic ethers [8], aliphatic esters of orthophosphoric acid [9-15], aliphatic, and cyclic sulfoxides... 

The crystal structures of Sm-Co and Sm-Fe-X (X=N, C) compounds of the lanthanide permanent magnets are based on the CaCus structure. SmCos has this structure, and the... 

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