Lanthanoids halides

MeOH, LaCl3, (MeO)3CH, 25°, 10 min, 80-100% yield/ Dimethyl acetals can be prepared efficlenlly under neutral conditions by catalysis with lanthanoid halides, but the results of the reaction with ketones are unpredictable. 

Numerous compounds adopt the PbFCl structure. These include, apart from fluoride chlorides, oxide halides MOX (M = Bi, lanthanoids, actinoids X = Cl, Br, I), hydride halides like CaHCl and many compounds with metallic properties like ZrSiS or NbSiAs. 

Bullock, J.I. and Tajmir-Riahi, H.A. (1978) Schiff-base complexes of the lanthanoids and actinoids. Part 1. Lanthanoid(III) halide complexes with the un-ionised form of iV,iV -ethyl-enebis(salicylideneimine) and related bases. Journal of the Chemical Society, Dalton Transactions, 36. 

Some inner transition metals are prepared from oxides on the research scale. Most of the lanthanoid metal are prepared from oxides via halides (see Section 9.2.2.3). A powerful reductant however, is required to produce Sm, Eu, Tm, and Yb, because of the stability of the difluorides of these metals. Since Sm, Eu, Tm, and Yb also have relatively high vapor pressures, they are best prepared by reduction of their oxides ... 

Oxides and halides can be reduced by hydrogen in some cases when a noble metal is present (a eoupled reduction). Lanthanoid or aetinoid noble metal alloys have been... 

Table 6.8 gives stability constants for the complexes [FeX] and [HgX] for different halide ions while the stabilities of the Fe complexes decrease in the order F > CP > Br, those of the Hg complexes increase in the order F < CP < Br < P. More generally, in examinations of stability constants by Ahrland, Chatt and Davies, and by Schwarzenbach, the same sequence as for Fe + was observed for the lighter s- and /i-block cations, other early J-block metal cations, and lanthanoid and actinoid metal cations. These cations were collectively termed class (a) cations. The same sequence as for Hg complexes was observed for halide complexes of the later J-block metal ions, tellurium, polonium and thallium. These ions were collectively called class (b) cations. Similar patterns were found for other donor atoms ligands with O- and iV-donors form more stable complexes with class (a) cations, while those with S- and F-donors form more stable complexes with class (b) cations. 

The carbides Ln2C3 and LnC2 are formed when the metals are heated with carbon. The LnC2 carbides adopt the same structure as CaC2 (see Section 13.7), but the C—C bonds (128 pm) are significantly lengthened (119 pm in CaC2). They are metallic conductors and are best formulated as Ln [C2] (e ). Lanthanoid borides were discussed in Section 12.10 halides are described below. 

Magnetic Order/Disorder in Category (ii) Lanthanoid Hydride Halides... 

In the reduced binary and ternary halides of the lanthanoids, the f electrons are well localized on the metal atoms. The coupling between the magnetic moments is weak in the case of insulators as can be seen from the low ordering temperatures of the saltlike trihalides whereby, for example, GdQj orders ferromagneti-cally at 2.2K. In the presence of extended M-M bonding, the conduction electrons provide a very efficient mechanism for coupling the moments via a RKKY... 

With respect to the synthesis of organometallic compounds of the lanthanoides with n -bonded organyls, the cyclopentadienyllanthanoide halides take a key position. The first dicyclopentadienyllanthanoide chlorides were obtained by the reaction of LnCl3 with only two equivalents of NaC5H5, or by redistribution of LnCl3 and Ln(C5H5)3 (42) ... 

Other relevant material is contained in reviews on homogeneous catalysis of organic reactions by transition metal complexes, highly reduced metal carbonyl complexes, phosphine complexes of the early transition metal complexes and the lanthanoids, metal NMR spectra of transition metal organometallic systems, the coordination chemistry of C-Nitroso-compounds, mono-Cp halide complexes of the d- and/-block, and organometallic chemistry in the gas phase. o... 

Lanthanoid halides LnCl3 and Lnp3 form tricyclopentadienyl complexes when alloyed with Cp2Mg (ca. 200°C) [122] or Cp2Be (ca. 70°C) [111]. The latter method has been developed for microgram quantities and has been used to prepare the promethium derivative ... 

The oxidation of divalent lanthanoids with substituted cyclopentadienyl ligands is easily realized with iodine [220] and hydrocarbon halides [28, 59, 60, 221] including fluorine derivatives [41]. 

Besides alkali metal ion, aluminium and magnesium may be used as a cation in the lanthanoid at -complexes (containing halide bridges or being separated ionic pair). The yttrium/aluminium complex is obtained in the reaction of ethyl-aluminium chloride with di(pentamethylcyclopentadienyl)yttrium chloride [201] ... 

Some chemical properties of naphthalene lanthanoid complexes obtained in the reaction of lanthanoid halides with lithium naphthalenide and similar compounds are summarized in Scheme 1 [65, 66, 78, 79]. 

Table VI.l. Lanthanoid amides, mixed halide/amides and similar complexes.

The compounds in which Ln atom is T -bonded with carborane, closo-lanthanoid-carboranes, can be obtained from the interaction of nido-7,8-dicarbollide dianion with lanthanoid halides [19, 24]. Samarium and ytterbium diiodides form a neutral monocage compound whereas trivalent lanthanoids give bis(dicarbollide) complexes [(C2B9H )2Gd] M (THF) (M = Na, BU4N). 

The interaction of equimolar quantities of lanthanoid halides and sodium derivatives affords mono-substituted complexes [39, 44, 52, 63] ... 

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