Organolanthanide complexes

A new class of organolanthanide complex has been reported from the metal-atom reaction of lanthanide atoms and butadiene (BD) or 2,-... 

The efficiency of the more readily accessible Cp 2Sm and Cp 2Sm(thf)2 complexes was also recognized [128, 129[. Further studies indicate that active catalyst precursors include organolanthanide complexes of the general formula Cp 2Ln-R (Ln = La, Nd, Sm, Yh, Lu) with R = H, T),- C5H5, CH(TMS)2, N(TMS)2 [131[. Generation of the catalytically active species is believed to occur via protonolysis of the Ln-R bond by the amine (Eq. 4.19). 

Metal vapor chemistry showed that the lanthanides had quite an extensive chemistry with unsaturated hydrocarbons. Some of the early surveys of metal vapor reactions with unsaturated hydrocarbons included some lanthanide metals and showed that reactivity was present for these metals (14-18). Subsequent synthetic studies in which the products were isolated and characterized led to some of the most unusual organolanthanide complexes currently known (19-28). 

The metal vapor reaction products differed from traditional organolanthanide complexes in many ways. First, the observed stoichiometries had low ligand to metal ratios. For example, the ytterbium and samarium 3-hexyne products (Reaction 4) had formal ligand to metal ratios of one, whereas most organolanthanides are commonly nine or ten coordinate (6-10). Second, the stoichiometries varied in an... 

Although the structures of these species were not determined, this metal vapor chemistry clearly showed that unsaturated hydrocarbons were viable reagents for lanthanides. Furthermore, this high energy technique showed that new regimes of organolanthanide complexes were accessible under the appropriate conditions. In addition, attempts to understand the synthesis of the products in reac-... 

Table 4. Polymerization of alkyl acrylates initiated by organolanthanide complexes... 

Table 7. Living polymerization of lactones with organolanthanide complexes...

The above organolanthanide complexes are less effective in obtaining high molecular weight polymers of (Lmethylpropiolactone. However, random... 

A positive evidence for a true cr-bonded organolanthanide complex is presented by Cotton et at. (32) in a crystal structure analysis of the anionic complex [Lu(III)-tetrakis-2,6-dimethylphenyl] . This anion crystaJUizes as [Li(I)-tetrakis-tetra-hydrofuran]+ salt, [Li(C4HgO)4]+ [Lu(C8H9)4] , in orthorhombic space group (P2i2i2i) with a = 15.093, 6 = 15.265 and c = 19.959 A and four formula units per unit cell. 

Cp Th(CH3)2] MgCl2.3oo (73) than for surface species 67. This proves the importance of cahonic surface species in polymerizahon reachons, since the number of active sites is >35% for the former. The reactivity of [Cp Th(CH3)2] MgCl2.3oo (73) was further examined toward propylene and/or 3,3 -dimethylbutene. This study rather suggests an aUyhc C-H bond activation/methane ehmination (Equation 12.1) followed by olefin inserhon than direct propylene insertion into the Th-R bond (Equahon 12.2). This observed reactivity is in agreement with that one described previously for organolanthanide complexes [CpJLnR] [142, 180, 181]. 

Anwander R (1996) Routes to Monomeric Lanthanide Alkoxides. 179 149-246 Anwander R, Herrmann WA (1996) Features of Organolanthanide Complexes. 179 1-32 Artymiuk PJ, Poirette AR, Rice DW, Willett P (1995) The Use of Graph Theoretical Methods for the Comparison of the Structures of Biological Macromolecules. 174 73-104 Astruc D (1991) The Use of p-Organoiron Sandwiches in Aromatic Chemistry. 160 47-96 Baerends EJ, see van Leeuwen R (1996) 180 107-168 Balbds LC, see Alonso JA (1996) 182 119-171... 

Cpsymmetric organolanthanide complexes exhibit moderate to good enantioselectivities in the hydrogenation and deuteration of styrene and 2-phenyl-1-butene.433 Cationic iridium-phosphanodihydrooxazole complexes are more efficient catalysts for the asymmetric hydrogenation of unfunctionalized aryl-substituted alkenes. The best catalyst (42) gives high yield (>99%) and excellent enantioselectivity (97% ee) in the hydrogenation of ( )-l,2-diphenyl-l-propene 434... 

Curry, R.J., George, M.R., Grossel, M.C., 2005. The potential of pyridine-2,6-dicarboxylic acid based organolanthanide complexes for efficient near infrared emission. In Zajya, H., Kafafi, H., Lane, P.A. (Eds.), Proc. SPIE, pp. 59371R-1-59371R-9. 

Michael reactions) [176], have been considered as alternative A-type spectator environments. The transfer of the catalytic substance of Schiff-base ligands, established in the work of Jacobsen [177], should further stimulate research in this area since organolanthanide complexes, as depicted in Scheme VII, are now available [178]. 

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