Lanthanide-carbon bonds

The bond angles at holmium and erbium as well as the lanthanide-carbon bond lengths in this electron deficient organolanthanide compounds (table 25) are comparable with those in other electron-deficient compounds with other metal atoms (Schumann and Bruncks, 1982 Schumann et al., 1984a). 

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

Kobayashi S (1999) Lanthanide Triflate-Catalyzed Carbon-Carbon Bond-Forming Reactions in Organic Synthesis. 2 63-118... 

Abstract Recent advances in the metal-catalyzed one-electron reduction reactions are described in this chapter. One-electron reduction induced by redox of early transition metals including titanium, vanadium, and lanthanide metals provides a variety of synthetic methods for carbon-carbon bond formation via radical species, as observed in the pinacol coupling, dehalogenation, and related radical-like reactions. The reversible catalytic cycle is achieved by a multi-component catalytic system in combination with a co-reductant and additives, which serve for the recycling, activation, and liberation of the real catalyst and the facilitation of the reaction steps. In the catalytic reductive transformations, the high stereoselectivity is attained by the design of the multi-component catalytic system. This article focuses mostly on the pinacol coupling reaction. 

Kobayashi S (1999) Lanthanide triflate-catalyzed carbon-carbon bond-forming reactions in organic synthesis. In Kobayashi S (ed) Topics in organometallic chemistry, vol 2, Lanthanides chemistry and use in organic synthesis. Springer, Heidelberg... 

The present volume is a non-thematic issue and includes seven contributions. The first chapter byAndreja Bakac presents a detailed account of the activation of dioxygen by transition metal complexes and the important role of atom transfer and free radical chemistry in aqueous solution. The second contribution comes from Jose Olabe, an expert in the field of pentacyanoferrate complexes, in which he describes the redox reactivity of coordinated ligands in such complexes. The third chapter deals with the activation of carbon dioxide and carbonato complexes as models for carbonic anhydrase, and comes from Anadi Dash and collaborators. This is followed by a contribution from Sasha Ryabov on the transition metal chemistry of glucose oxidase, horseradish peroxidase and related enzymes. In chapter five Alexandra Masarwa and Dan Meyerstein present a detailed report on the properties of transition metal complexes containing metal-carbon bonds in aqueous solution. Ivana Ivanovic and Katarina Andjelkovic describe the importance of hepta-coordination in complexes of 3d transition metals in the subsequent contribution. The final chapter by Sally Brooker and co-workers is devoted to the application of lanthanide complexes as luminescent biolabels, an exciting new area of development. 

The readily available system Ln(OiPr)3 made the running for the others in carbon-carbon bond generations and functional group modifications. Meanwhile, the steadily growing demand for stereo- and enantioselective reagents has also affected the lanthanide elements and as a result more sophisticated ligands have been introduced (Fig. 35A-G). 

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... 

IOB alone can oxidize some alcohols, but catalysed oxidations are much more efficient. Thus, in the presence of RuCl2(PPh3)2 primary aliphatic alcohols were oxidized cleanly to aldehydes, at room temperature the use of m-iodosylbenzoic acid instead of IOB considerably increased the yields for example, hexanal was formed from hexanol quantitatively (by GC) [19], Another catalytic system involved the use of simple lanthanide salts such as ytterbium triacetate [20]. Cyclic y-stannyl alcohols, readily available from cyclic vinyl ketones and Bu3SnLi, underwent oxidation accompanied by carbon-carbon bond cleavage (Grab fragmentation), when treated with IOB.BF3 and DCC. The products were unsaturated aldehydes or ketones. 

Bismuth(m) salts, such as BiCl3, BiBr3, Bi(OCOR)3, Bi(N03)3, Bi(OTf)3, and Bi(NTf2)3, have been used as Lewis acid catalysts to mediate a variety of carbon-carbon bond-forming reactions.85 In some cases, true catalysts differ from the bismuth salts initially added. The most effective and frequently used catalyst is Bi(OTf)3, which is obtained as a hydrated or dehydrated form depending on the preparation methods.86,86a,86b Like lanthanide triflates, Bi(OTf)3 is water stable and reusable. 

The addition of sp3 or sp2 carbon-centred radicals to unsaturated carbon carbon bonds is yet another class of synthetically useful reactions promoted by the low-valent lanthanide reagent Sml2. Halides and sulfones are the most common functional groups used as precursors to radicals, although other groups have also been successfully employed. Although the intermolecular variant of this reaction has found only limited application, intramolecular variants can be highly successful. In most of these cyclisation events, the... 

There have been no reports of SO2 insertion into a metal-carbon bond of the lanthanide and actinide elements. 

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