Cationic Allyl Complexes of the Rare‐Earth Metals: Synthesis,Structural Characterization,and 1,3‐Butadiene Polymerization Catalysis |
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| Authors: | Dominique Robert Dr Elise Abinet Dipl‐Chem Thomas P Spaniol Dr Jun Okuda Prof Dr |
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| Institution: | Institut für Anorganische Chemie, RWTH Aachen University, Landoltweg 1, 52074 Aachen (Germany), Fax: (+49)?241‐80‐92644 |
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| Abstract: | Monocationic bis‐allyl complexes Ln(η3‐C3H5)2(thf)3]+B(C6X5)4]? (Ln=Y, La, Nd; X=H, F) and dicationic mono‐allyl complexes of yttrium and the early lanthanides Ln(η3‐C3H5)(thf)6]2+BPh4]2? (Ln=La, Nd) were prepared by protonolysis of the tris‐allyl complexes Ln(η3‐C3H5)3(diox)] (Ln=Y, La, Ce, Pr, Nd, Sm; diox=1,4‐dioxane) isolated as a 1,4‐dioxane‐bridged dimer (Ln=Ce) or THF adducts Ln(η3‐C3H5)3(thf)2] (Ln=Ce, Pr). Allyl abstraction from the neutral tris‐allyl complex by a Lewis acid, ER3 (Al(CH2SiMe3)3, BPh3) gave the ion pair Ln(η3‐C3H5)2(thf)3]+ER3(η1‐CH2CH?CH2)]? (Ln=Y, La; ER3=Al(CH2SiMe3)3, BPh3). Benzophenone inserts into the La? Callyl bond of La(η3‐C3H5)2(thf)3]+BPh4]? to form the alkoxy complex La{OCPh2(CH2CH?CH2)}2(thf)3]+BPh4]?. The monocationic half‐sandwich complexes Ln(η5‐C5Me4SiMe3)(η3‐C3H5)(thf)2]+B(C6X5)4]? (Ln=Y, La; X=H, F) were synthesized from the neutral precursors Ln(η5‐C5Me4SiMe3)(η3‐C3H5)2(thf)] by protonolysis. For 1,3‐butadiene polymerization catalysis, the yttrium‐based systems were more active than the corresponding lanthanum or neodymium homologues, giving polybutadiene with approximately 90 % 1,4‐cis stereoselectivity. |
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| Keywords: | allyl ligands butadiene cationic complexes lanthanides polymerization |
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