Lanthanides, organo- compounds

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. ... 

Mono(organo)nickel compounds, via oxidative addition, 8, 44 Monoorganotin hydroxides, preparation, 3, 850 Monoorganotin oxides, preparation, 3, 850 Mono(pentamethylcyclopentadienyl) actinide(IV) compounds, reactions, 4, 207 Mono(pentamethylcyclopentadienyl) lanthanide(III) compounds, synthesis and characteristics, 4, 66 Mono(pentamethylcyclopentadienyl) uranium(IV) sulfido complex, synthesis, 4, 207-208 Mono(phenoxy-aldehyde) trichlorides, with Zr(IV),... 

Lanthanide metallocene compounds are also active catalysts for the dimerization of terminal alkynes, giving predominantly the linear head-to-head enyne dimer with a double bond of E configuration [17]. In recent years, however, novel organo-lanthanide [13] and organoactinide [18, 19] systems have shown their ability to produce, with high selectivity, Z and geminal enyne products, respectively. 

We can visualise the capability of suitable lanthanide (Ln) compounds (J, 6), e.g. as homogeneous catalysts with respect to olefins, by invoking similar intermediates. Although the series of reportedly catalytically active Ln-complexes spans from the pure trihalide via tris(B-diketonato)complexes to the organo-metallic tris(cyclopentadienyl) and tetra(allyl)complexes (8), respectively, no really optimal combination of ligands on a Ln-element has been found so far. Promising aspects are, however, based on some evidence for "reaction steering" in that either cis- or trans-polybutadienes can be obtained from 1,3-dienes, and either polymers or metathesis products from monoolefins, respectively (Table I). 

Synthetic routes include anionic, cationic, zwitterionic, and coordination polymerization. A wide range of organometallic compounds has been proven as effective initiators/catalysts for ROP of lactones Lewis acids (e.g., A1C13, BF3, and ZnCl2) [150], alkali metal compounds [160], organozinc compounds [161], tin compounds of which stannous octoate [also referred to as stannous-2-ethylhexanoate or tin(II) octoate] is the most well known [162-164], organo-acid rare earth compounds such as lanthanide complexes [165-168], and aluminum alkoxides [169]. Stannous-2-ethylhexanoate is one of the most extensively used initiators for the coordination polymerization of biomaterials, thanks to the ease of polymerization and because it has been approved by the FDA [170]. 

Organolanthanide(III) compounds form the bulk of all the known organo-lanthanides. However, in addition to the + 3 oxidation state, the + 2 oxidation state is chemically accessible for samarium, europium and ytterbium (an organocerium(II) [1] and an organoneodynium(II) [2] complex have also been reported but not structurally confirmed) and the +4 oxidation state is accessible for cerium. A few organolanthanide(O) compounds are also known,... 

Although the preponderance of recent reports centres upon some inner transition metal ions (lanthanides), one prominent investigation features water exchange on a first row organo-transition metal compound. Organometallic aqua ions in which a transition metal ion... 

Unlike the lanthanide complexes CpsLn, and many degradation products, Cp3 nLnXn, some actinide, and the majority of d-block metal, cyclopentadienides are not susceptible to reaction (1). A reasonably good test for the reactivity of metal-bonded Cp with H-acids consists in the addition of water or methanol. While all known lanthanide complexes will immediately be decomposed, many organo-uranium compounds of the type CP3UX either simply add H2O and/or undergo substitution of X (13) ... 

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