New bis(allyl)(diketiminato) and tris(allyl) lanthanide complexes and their reactivity in the polymerization of polar monomers

Luis F. Sánchez-Barba, David L. Hughes, Simon M. Humphrey, M. Bochmann

Research output: Contribution to journalArticlepeer-review

109 Citations (Scopus)


The reaction of LnCl3(THF)n (Ln = La, n = 4; Ln = Y, Sm, Nd, n = 3) with 3 equiv of allylMgCl in THF/1,4-dioxane followed by crystallization in 1,4-dioxane/toluene proceeds in very high yields to give the tris(?3-allyl) complexes [La(?3-C3H5)3(?1-dioxane)]2(µ-dioxane) and [Ln(?3-C3H5)3(µ-dioxane)]8 (Ln = Y, 1; Sm, 2; Nd). Improved one-pot syntheses for the tris(?3-allyl) lanthanum and neodymium compounds are reported. The crystal structures of 1 and 2 show that the compounds consist of distorted square-pyramidal lanthanide centers in linear polymer chains. The reaction of [La(?3-C3H5)3(?1-dioxane)]2(µ-dioxane) and [Ln(?3-C3H5)3(µ-dioxane)]8 with the diketimine ligand 2-(2,6-diisopropylphenyl)amino-4-(2,6-diisopropylphenyl)imino-2-pentene (BDI-H) in THF at 60 °C generates cleanly the ß-diketiminato complexes Ln(?3-C3H5)2{?2-HC(MeCNAr)2} (Ar = 2,6-C6H3iPr2; Ln = La, 3; Y, 4; Sm, 5; Nd, 6) with propene elimination. The crystal structure of 5 shows a distorted tetrahedral SmN2(allyl)2 core, with the samarium atom positioned 1.438(4) Å out of the C3N2 ligand plane. All complexes are highly effective single-component catalysts for the ring-opening polymerization of e-caprolactone and rac-lactide. Polymer end group analysis shows that the polymerization process is initiated by allyl transfer to monomer.
Original languageEnglish
Pages (from-to)3792-3799
Number of pages8
Issue number15
Publication statusPublished - 2005

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