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Organolanthanide complexes of heptamethylindenyl and related ligands : synthesis, reactions and catalytic properties
Heptamethylindenyl complexes of lanthanum, neodymium and erbium containing one, two or three heptamethylindenyl ligands can be synthesized from the reaction of alkali metal heptamethylindenide salts and the appropriate lanthanide chlorides in THF. The resulting lanthanide complexes can be characterized spectroscopically. The heptamethylindenyl ligand in the complex has been determined to have a pentahapto or trihapto structure using ('13)C NMR spectroscopy and the technique of isotopic perturbation of equilibrium. Tris(heptamethylindenyl)lanthanum and heptamethylindenyllanthanum dichloride can be obtained as pure complexes. However, bis(heptamethylindenyl)lanthanum chloride undergoes a disproportionation reaction to generate tris(heptamethylindenyl)lanthanum and heptamethylindenyllanthanum dichloride. These complexes are reactive species, readily decomposing in the presence of protic substances such as water, alcohols and even DMSO. The reaction of these complexes with nucleophiles such as sodium amide, methyllithium and methylmagnesium halides have been studied. In all of these cases, exchange occurs and heptamethylindenylsodium, heptamethylindenyllithium or heptamethylindenylmagnesium halides are formed. In the latter two cases, species tentatively indentified as methyl organolanthanides were detectable by ('13)C NMR spectroscopy. Potential catalytic applications of these lanthanide complexes in transformations of olefins have also been studied. In the presence of these complexes and organolithium or organoaluminum compounds, 1,3-butadiene polymerization, ethylene polymerization and 1-heptene, 2-pentene or 1,7-octadiene metathesis or dimerization reactions have been observed. In the case of 1,3-butadiene polymerization, the observed 1,4-polybutadiene is formed catalytically. The microstructure of the diene polymer formed using these lanthanide catalysts has also been shown to vary depending on the choice of organoaluminum compounds used in these polymerizations. A d-transition metal complex bis(heptamethylindenyl)iron(II), and some lanthanide complexes of cyclopentadienyl and indenyl ligands have also been prepared and their properties have been compared with the heptamethylindenyl lanthanide complexes. Some polymer-bound lanthanide species such as cerium polystyrene carboxylate have been prepared and used as catalysts for 1,3-butadiene polymerization. The high stereospecificity of lanthanide catalysts has been retained by the polymer-bound lanthanide catalysts.
Chen, Li-Ba (1983). Organolanthanide complexes of heptamethylindenyl and related ligands : synthesis, reactions and catalytic properties. Texas A&M University. Texas A&M University. Libraries. Available electronically from
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