Lanthanide complex with allyl

Lactones, via indium compounds, 9, 686 Lactonizations, via ruthenium catalysts, 10, 160 Ladder polysilanes, preparation and properties, 3, 639 Lanthanacarboranes, synthesis, 3, 249 Lanthanide complexes with alkenyls, 4, 17 with alkyls, 4, 7 with alkynyls, 4, 17 with allyls, 4, 19 with arenes, 4, 119, 4, 118 and aromatic C-F bond activation, 1, 738 bis(Cp ), 4, 73... 

In addtion to Sm metal, Cp 2Sm(TFlF)B (n = 2 or 0) can be a good starting material for allylsamarium generation. In the case of Cp 2Sm(THF) (n = 2 or 0), allylic ethers are useful precursors since they are able to coordinate to the low-valent lanthanide metal via the internal oxygen. Samarium complexes 45 react with allyl benzyl ether 46 to produce allylsamarium complex 47 and benzyloxide 48 as illustrated in Equation (9).26... 

The allyl group is able to form both a- and jr-bonded complexes with the actinides. The 71 complexes will be considered here because of the similarities of the homoal-lyls with the lanthanide and actinide homoalkyls. The limiting modes of bonding in metal allyl complexes and the ratio of PMR intensities from magnetically equi valent protons are illustrated in Fig. 14. 

Lanthanide triflates, for allylic tin reactions, 9, 354 Laser beam heating, in metal vapor synthesis, 1, 224 Laser methods, in mechanistic studies, 1, 248 Laser photochemical vapor deposition, with organometallic complexes, 1, 259... 

Although heterobimetallic complexes with alkylated rare-earth metal centers were proposed to promote 1,3-diene polymerization via an allyl insertion mechanism, details of the polymerization mechanism and of the structure of the catalytically active center(s) are rare [58,83,118-125]. Moreover, until now, the interaction of the cationizing chloride-donating reagent with alkylated rare-earth metal centers is not well-understood. Lanthanide carboxylate complexes, which are used in the industrial-scale polymerization of butadiene and isoprene, are generally derived from octanoic, versatic, and... 

Some of the applications of the organometallic compounds of lanthanides are as catalysts for (i) stereo specific polymerization of diolefins and in particular to obtain high yields of 1,4-ci.v-polybutadiene and 1,4-cw-polyisoprene and copolymer of the two monomers. The order of effectiveness of the rare earths as catalysts is Nd > Ce, Pr < Sm, Eu. The nature of halogen of the Lewis acid affecting the catalytic activity is in the order Br > Cl > I > F. Detailed work on the activity of cerium octanoate-AlR3-halide showed stereo specificity with cerium as the primary regulator. Cerium is thought to form jr-allyl or 7r-crotyl complexes with butadiene. 

Metal rf-inline complexes with various transition metals [1-10] and lanthanides [11,12] are well known in the literature. Early transition metal if-imine complexes have attracted attention as a-amino carbanion equivalents. Zirconium rf-imine complexes, or zirconaaziridines (the names describe different resonance structures), are readily accessible and have been applied in organic synthesis in view of the umpolung [13] of their carbons whereas imines readily react with nucleophiles, zirconaaziridines undergo the insertion of electrophilic reagents. Accessible compounds include heterocycles and nitrogen-containing products such as allylic amines, diamines, amino alcohols, amino amides, amino am-idines, and amino acid esters. Asymmetric syntheses of allylic amines and a-amino acid esters have even been carried out. The mechanism of such transformations has implications not only for imine complexes, but also for the related aldehyde and ketone complexes [14-16]. The synthesis and properties of zirconaaziridines and their applications toward organic transformations will be discussed in this chapter. 

Following the synthesis of tris(cyclopentadienyl) lanthanide complexes, the first examples of organolanthanide derivatives, a vast number of organolanthanide it-complexes with cyclopen-tadienyl (Cp), indenyl (Ind), cyclooctatetraenyl (COT), and related substituted derivatives have been prepared and extensively reviewed [3]. Here we will briefly discuss cyclopentadienyl and allyl derivatives as representatives of organolanthanide K-complexes. 

Reaction of tetranuclear lanthanide octahydrides with styrene provides lanthanide benzylic allyl heptahydride complexes through the insertion of a styrene molecule into one Ln-H bond. The lanthanide benzylic allyl complexes can be considered as the intermediates of styrene hydrogenation. Indeed, both the lanthanide octahydrides and the lanthanide benzylic allyl complexes can catalyze styrene hydrogenation efficiently in the presence of H2 [89]. Lanthanide hydrides react with 1,3-cyclohexadiene to form lanthanide allylic complexes via 1,4-addition [90]. However, these lanthanide hydride clusters can not catalyze the polymerization of styrene and 1,4-cyclohexadiene. 

Edelmann FT (1996) Rare Earth Complexes with Hetero allylic Ligands. 179 113-148 Edelmann FT (1996) Lanthanide Metallocenes in Homogeneous Catalysis. 179 247-276 Effenhauser CS (1998) Integrated Chip-Based Microcolumn Separation Systems. 194 51-82 Ehrfeld W, Hessel V, Lehr H (1998) Microreactors for Chemical Synthesis and Biotechnology -... 

Scandium group elements as well as the lanthanides form allyl complexes in which the central atom has H- 3 oxidation state, while the actinides give compounds possessing + 4 oxidation states (Table 7.14). These complexes are formed by reactions of metal halides with allyl compounds of magnesium, lithium, tin, etc. " " ... 

Very recently, Hou and coworkers have reported that rare earth half-metallocene complexes (Figure 14.16, 85-88) activated with [Ph3C] [B(C6F5)4] afford highly active systems for syndio-specific styrene polymerization, producing sPS with high syndiotacticities rrrr > 99%) and rather narrow polydispersities (Mw/Mn = 1.29-1.55). The activity of scandium complex 85 is comparable with that for the most active titanium catalysts (1.36 x 10 g sPS/(mol Sc-h)). The neutral allyl lanthanide complexes 89-92 (Figure 14.16) in the absence of a cocatalyst are also active for the syndiospecific polymerization of styrene (rrrr > 99%), but with lower activities that are in the order... 

The lanthanides and actinides also form a wide range of complexes with unsaturated organic ligands including allyls, cyclopentadienyls and cycloocta-tetraene derivatives. The bonding is strongly polar. Coordination numbers are determined largely by steric requirements around the metal centre. 

To conclude this section, one should highlight recent studies on N-functionaUzed cyclopentadienyl ligands. The [(Cp )Ln(AlMe4)2] precatalysts (40), generated via a protonolysis reaction of Ln(AlMe4)3 with HCp (Scheme 24), were reported to be active in IP polymerization under various conditions (cocatalyst, solvent, temperature, time) and the best results are summarized in Table 3 [125]. Allyl-lanthanides complexes of an N-functionalized Cp (N = amino) were also reported by Cui et al. to be efficient catalysts for the living and block copolymerization of IP in the presence of organoaluminum (5-70 equiv.) and boron cocatalysts [126]. 

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