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Lanthanide-arene complexes

The rapid development of cyclopentadienyl chemistry of the early transition metals, lanthanides and actinides is a noteable feature of the 1986 literature. In arene chemistry, further reports of uranium arene complexes and the report of the first lanthanide arene complex confirm that these complexes are isolated examples of an emerging class. [Pg.351]

Both dimetallic and trimetallic chloro-bridged uranium hexamethylbenzene complexes have been reported and the structure of the first lanthanide arene complex (hmb)Sm(AlCl3)3 described. ... [Pg.375]

Although several phenyl derivatives of the lanthanides and actinides have been characterized, only one re-arene complex of the / transition metals is known to date. This is the uranium(III) benzene complex, U(AlCl4)s CeHe 153), prepared by the combination of uranium tetrachloride, aluminum trichloride and aluminum powder in refluxing benzene, the Fischer-Hafner method [154). The molecular geometry of the complex is shown in Fig. 18. [Pg.62]

The synthetic potential of transition metal atoms in organometallic chemistry was first demonstrated by the formation of dibenzenechrom-ium (127). Apart from chromium, Ti, V, Nb, Mo, W, Mn, and Fe atoms each form well-defined complexes with arenes on condensation at low temperatures. Interaction has also been observed between arenes and the vapors of Co, Ni, and some lanthanides. Most important, the synthesis of metal-arene complexes from metal vapors has been successful with a wide range of substituted benzenes, providing routes to many compounds inaccessible by conventional reductive preparations of metal-arene compounds. [Pg.72]

Corresponding 5-coordinate samarium complexes can also be accomplished (Table 5) [74,75] and heteroatom stabilization of the strongly reducing Sm(II) was observed in the ate complex [KSm(OC6H3tBu2-2,6-Me-4)3(THF)]n [75]. Indefinite chains or higher aggregations by K arene interactions seems to be a common coordination mode in lanthanide aryloxide complexes. [Pg.167]

Dibenzenechromium, which forms dark brown crystals, is much more sensitive to air than is ferrocene, with which it is isoelectronic it does not survive the reaction conditions of aromatic substitution. Structural studies on arene complexes show that the C—C bond lengths are usually equivalent, or nearly so. Many other transition metals, including some lanthanides and uranium form arene complexes, and... [Pg.690]

However, in contrast to the lanthanides, no arene complexes in a formal zero oxidation state have been isolated. [Pg.222]

Other signiflcant complexes of this type, containing one or more lanthanides, are formed by calixarenes (see Calixarenes) Much of this work has been prompted by their potential in separating lanthanides from uranium and other metals. A calixarene ligand with two amide substituents has been synthesised as an extractant for lanthanides dimeric Sm and Eu and monomeric Eu complexes have been prepared. Another calixarene, with four phosphine oxides attached, has been fixed to silica particles and the resulting system has been found to give very efficient extraction of Eu + and Ce + from simulated waste. A calix[4]arene complex of Gd + binds... [Pg.4220]

There are just few examples of authentic lanthanide complexes in the oxidation state zero. Bis(arene) complexes of the lanthanides (l,3,5- Bu3C6H3)2Ln (Ln = Sc, Y, La, Nd, Pr, Sm, Gd, Tb, Dy, Ho, Er, Lu) have been synthesized by cocondensation of metal vapors (see Metal Vapor Synthesis of Transition Metal Compounds) with 1,3,5-tri(ferf-butyl)benzene at 75 K. A sandwich structure with coplanar arene ligands has been proven by X-ray crystal structure analysis of the Gd and Ho complexes (Figure 86a). [Pg.4272]

Kajiwara, T, Iki, N., and Yamashita, M. (2007) Transition metal and lanthanide cluster complexes constmcted with thiacahx[n]arene and its derivatives. Coordination Chemistry Reviews, 251, 1734-1746. [Pg.267]

Beer, P.D., Szemes, F., Passaniti, P., and Maestri, M. (2004) Luminescent ruthenium(II) bipyridine-calix[4]arene complexes as receptors for lanthanide cations. Inorganic Chemistry, 43, 3965... [Pg.526]

Fig. 5. Arene complexes of low-valent lanthanide elements obtained by co-condensation methods... Fig. 5. Arene complexes of low-valent lanthanide elements obtained by co-condensation methods...
Related complexes are obtained with Pd, where one face of a benzene ring is shared by two Pd atoms . Mono-f/ -benzene ligands on a pentacobalt cluster also form from the aluminum halide-aluminum metal conditions . The preparation of -arene complexes of the lanthanides and actinides has been more diflScult, presumably because of the proclivity of these metals to form ionic bonds. Reactions between hexamethylbenzene and metal halides in the presence of AlClj-Al or AlCl-Zn reagents in the isolation of a mononuclear Sm complex, in addition to di- and trinuclear U complexes. ... [Pg.185]

Transition metal and lanthanide cluster complexes constructed with thia-calix[n]arene and its derivatives 07CCR1734. [Pg.89]

The reduction in the propagation rate constant under the effect of aromatic hydrocarbon is due to hydrocarbon and diene monomer competing for coordination at the active centre. The effect of slowing down the polymerisation reaction is due to the fact that aromatic hydrocarbon forms an arene complex with the lanthanide atom. The higher the 7t-electron-donating ability of the aromatic hydrocarbon, the lower the rate constant for polydiene chain propagation. Thus, the rate of polymerisation of dienes decreases in the series benzene > toluene > xylene [11, 14, 26, 28]. [Pg.80]

The hydroamination of olefins has been shown to occur by the sequence of oxidative addition, migratory insertion, and reductive elimination in only one case. Because amines are nucleophilic, pathways are available for the additions of amines to olefins and alkynes that are unavailable for the additions of HCN, silanes, and boranes. For example, hydroaminations catalyzed by late transition metals are thought to occur in many cases by nucleophilic attack on coordinated alkenes and alkynes or by nucleophilic attack on ir-allyl, iT-benzyl, or TT-arene complexes. Hydroaminations catalyzed by lanthanide and actinide complexes occur by insertion of an olefin into a metal-amide bond. Finally, hydroamination catalyzed by dP group 4 metals have been shown to occur through imido complexes. In this case, a [2+2] cycloaddition forms the C-N bond, and protonolysis of the resulting metallacycle releases the organic product. [Pg.735]

Harrowfield et al. [37-39] have described the structures of several dimethyl sulfoxide adducts of homo bimetallic complexes of rare earth metal cations with p-/e rt-butyl calix[8]arene and i /i-ferrocene derivatives of bridged calix[4]arenes. Ludwing et al. [40] described the solvent extraction behavior of three calixarene-type cyclophanes toward trivalent lanthanides La (Ln = La, Nd, Eu, Er, and Yb). By using p-tert-huty ca-lix[6Jarene hexacarboxylic acid, the lanthanides were extracted from the aqueous phase at pH 2-3.5. The ex-tractability is Nb, Eu > La > Er > Yb. [Pg.342]


See other pages where Lanthanide-arene complexes is mentioned: [Pg.424]    [Pg.470]    [Pg.424]    [Pg.470]    [Pg.452]    [Pg.154]    [Pg.144]    [Pg.4273]    [Pg.252]    [Pg.328]    [Pg.496]    [Pg.161]    [Pg.485]    [Pg.3]    [Pg.74]    [Pg.4272]    [Pg.462]    [Pg.49]    [Pg.275]    [Pg.296]    [Pg.251]    [Pg.266]    [Pg.388]    [Pg.388]    [Pg.389]    [Pg.310]    [Pg.334]   
See also in sourсe #XX -- [ Pg.470 ]




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