Lanthanide iodides

Instead of using an aldehyde for trapping the primarily formed enolate, there are also a few examples which involve an imino acceptor in the second anionic step. The Collin group used a lanthanide iodide-mediated reaction of a ketene silyl acetal... 

Moeller and Vicentini (48) have reported the complexes of DMA with lanthanide perchlorates in which the number of DMA molecules per metal ion decreases from eight for La(III)—Nd(III) to six for Tm(III)—Lu(III).apparently due to the decrease in the cationic size. The complexes of the intermediate metal ions have seven molecules of DMA in their composition. Complexes of lanthanide chlorides with DMA (49, 50) exhibit a decrease in L M from 4 1 to 3 1 through 3.5 1. These complexes probably have bridging DMA molecules. The corresponding complexes with lanthanide iodides (51), isothiocyanates (52), hexafluorophosphates (57), nitrates (54, 55), and perrhenates (49, 56) also show decreasing L M with decreasing size of the lanthanide ion. However, complexes of DMA with lanthanide bromides (55) do not show such a trend. Krishnamurthy and Soundararajan (41) have reported the complexes of DPF with lanthanide perchlorates of the composition [Ln(DPF)6]... 

A number of methyl substituted PyO have been tried as ligands for coordination with the lanthanides. Depending on the position of the substituent, these ligands impart different degrees of steric strain for the formation of complexes. Since substituents in the 4 or 3 position do not introduce substantial steric hindrance to coordination, Harrison and Watson (160) could synthesize octakis-4-MePyO complexes. Subsequently, Koppikar and Soundararajan (161) could also synthesize octakis-3-MePyO complexes with lanthanide perchlorates. Complexes of 4-MePyO (162, 163) and 3-MePyO (164, 165) with lanthanide iodides and bromides also have a L M of 8 1. 

Complexes of lanthanide chlorides 156,173), bromides (256), and iodides 174) with 2,6-DMePyO have also been prepared and characterized. The presence of bridging 2,6- DMePyO molecules has been suggested in the complexes of lanthanide iodides. Vicentini and De Oliveira (2 73) have reported tetrakis-2,6-DMePyO complexes with lanthanide nitrates. However, by changing the method of synthesis, tris-2,6-DMePyO complexes with the lanthanide nitrates could be prepared in this laboratory (252). All the nitrate groups in the tris-2,6-DMePyO complexes are bidentate. In the 2,4,6-TMePyO complexes (252) also the nitrate groups are coordinated to the lanthanide ion in a bidentate fashion. 

Samarium and other lanthanide iodides have been used to promote a range of Mukaiyama aldol and Michael reactions. The syntheses show promise as enantio-selective transformations, but the precise mechanistic role of the lanthanide has yet to be elucidated. 

Lanthanide iodide silicides, 200 Lanthanide metals, 200 Lanthanide nitrobenzoates, 200 Lanthanide—transition metal alloy hydrides, 201 Lassaigne test, 201 Lead salts of nitro compounds, 201 Lecture demonstrations, 202 Light alloys, 202 Lime fusion, 202 Linseed oil, 202 Liquefied gases, 203 Liquefied natural gas, 203 Liquefied petroleum gases, 203 Liquid air, 204 Liquid nitrogen cooling, 205 Lithium peralkyluranates, 205 Lubricants, 205 Lycopodium powder, 205... 

Ln-Halides. The complexation/solvation criteria is just one reason why lanthanide halides are the most common precursors in organolanthanide chemistry. In this evaluation, lanthanide iodides are often preferred to bromides and chlorides, however the former are more difficult to synthesize and are much more expensive [96f. Waterfree, solid Ln-halides are ionic substances with high melting points which immediately absorb water when exposed to air, forming hydrates (I > Br > Cl ). Therefore, they have to be handled under an inert gas atmosphere. The main use of the halides is for the production of pure metals [96]. Some methods of preparing Ln(III)-chlorides are summarized in Scheme IV [96],... 

A few classic heteroleptic complexes were sythesized involving additional lanthanide iodide [146], cyclopentadienyl [147,149], amide [141], alkoxide... 

Table 2 Polymerization of isoprene with divalent lanthanide iodides Lnl2 (Ln = Nd, Sm, Dy, Tm) and Lni2(THF)x (Ln = Sm, Tm) as initiators (from [95])...

Figure 4.19 The structures of four complexes [Sml(p.-I)(17)3]2, Sm(17)8l3, [(17)4Sm]( x-OH) 3(p.3-OH)2 l4, and [(17)5Sm(p.-OH)]2l4 [34], (Reproduced with permission from WJ. Evans, GW. Rabe and J.W. Ziller, Utility of N-methylimidazole in isolating crystalline lanthanide iodide and hydroxide complexes crystallographic characterization of octasolvated [Sm(N-MeIm)8]I3 and polymetallic [Sml( x-I)(N-Melm)3]2, [(N-MeIm)5Sm( X-OH)]2l4, and [(N-MeIm)4Sm(tJi-OH)]3(tJi3-OH)2 l4, Inorganic Chemistry, 33, 3072, 1994. 1994 American Chemical Society.)...

The first non-classical divalent lanthanide iodide Tml2(DME)3 (DME = dimethoxyethane), which is prepared by the reaction of thulium metal with iodine under argon (Equation 8.33), was reported in 1997 [101]. Subsequently, Dyl2(DME)3 andNdl2(THF)5 have been synthesized by an analogous manner. The success of the synthesis of non-classical divalent lanthanide iodides opens up a new area in divalent lanthanide chemistry [102, 103]. 

Tml2(DME)3, Dyl2 (DME)3, and Ndl2(THF)5 have similar structures to those of the classical divalent lanthanide iodides. However, metathesis reaction with these iodides usually affords not a divalent complex but a trivalent lanthanide complex instead, because of their strong reductive ability [102], To date, only one structurally characterized divalent organothulium complex has been synthesized by metathesis reaction (Equation 8.34) [104]. 

Catalytic hydroboration is a new methodology of great synthetic potential. The reaction is usually carried out with catecholborane in the presence of rhodium, palladium, iridium and ruthenium compounds.2 In contrast to olefins, very little is known on catalytic hydroboration of conjugated dienes and enynes. Our earlier studies on the uncatalyzed monohydroboration of conjugated dienes,6 reports on the hydroboration of 1-decene with catecholborane catalyzed by lanthanide iodides,7 and monohydroboration of 1,3-enynes in the presence of palladium compounds,8 prompted us to search for other transition metal catalysts for monohydroboration of conjugated dienes and enynes 9 10... 

In a search for a suitable catalyst we started with lanthanide iodides, monitoring by 1 B NMR analysis the stability of 1 M catecholborane solutions in tetrahydrofliran containing 10 molar % of SmL, f-BuOSmL, and Lat. Unfortunately, in the presence of these iodides a signal corresponding to borane-tetrahydrofiiran, and other signals, appeared in less than 1 h. In contrast, catecholborane in tetrahydrofliran was stable in the presence of nickel(II), cobalt(II) and iron(H) chloride complexes with dppe. 

Bipyridyl complexes with lanthanide bromides do not seem to have received attention, but the first lanthanide iodide complexes were reported in 1999. In a comparative study with UI3, complexation of bipy with (Ln = Ce, Nd) was investigated. UI3 and Cels both form 1 1 and 1 2 complexes in solution, with a 1 3 complex at high bipy concentrations, whereas Ndls only forms a 1 2 complex. The structure of [Cel3(bipy)2(py)].5py.bipy was reported it has eight-coordinate Ce, with Ce—(bipy) = 2.67(3) A, Ce—I = (average 3.23(3) A) and Ce—N 2.678(9) A. Reaction of [Ndl3(py)4] and bipy in attempts to make the Nd analogue resulted in dimeric [(bipy)3Nd(/i-OH)2Nd(bipy)3]l4 3Py, presumably due to inadvertent hydrolysis. ... 

Namy, J. L., Girard, P., Kagan, H. B. A new preparation of some divalent lanthanide iodides and their usefulness in organic synthesis. 

The dimeric mono(cyclooctatetraenyl)lanthanide chlorides [(COT)Ln(/r-Cl)(THF)2]2 are long known and still represent the most useful precursors in (COT)Ln chemistry. A recently reported alternative preparation of the Sm derivative involves the reaction of samarium metal with COT in THF in the presence of a small amount of I IgCL. The molecular structure of [(COT)Sm(/i-CI)(TT 11 )2]2 has been determined.805,806 Iodo-(cyclooctatetraenyl)lanthanide iodides of the type (COT)Lnl(TIIF) (Ln = La, Ce, Pr, n = 3 Ln = Nd, n = 2 Ln = Sm, n l) are readily accessible in a one-pot reaction of metallic lanthanides with COT in the presence of an equimolar amount of iodine. Bromo- and chloro-bridged binuclear complexes of samarium, [(COT)Sm(/.t-X)(THF )2]2 (X = Br, Cl), were also prepared by the reaction of samarium metal with COT in the presence of 1,2-dibromoethane or Ph3PCl2, respectively.807 Alternatively, the iodo complexes (COT)LnI(THF)3 (Ln = Nd, Sm) can be synthesized directly from the lanthanide triiodides and K2COT. The molecular structure of (COT)Ndl(THF)3 has been determined by X-ray diffraction.808 A clean preparation of the monomeric half-sandwich complex (GOT)TmI(THF)2 involves treatment of Tml2 with equimolar amounts of COT in THF at room temperature (Scheme 227). The product was isolated as red crystals in 75% yield.628... 

Direct hydrolysis of lanthanide iodides and perchlorates has also been reported. Cluster-type basic lanthanide iodides [R6(/i3-0H)8(/i6 0)... 

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