Highly Reactive Organolanthanides. Synthesis, Chemistry, and Structures of 4f Hydrocarbyls and Hydrides with Chelating Bis(polymethylcyclopentadienyl) Ligands

Gerald Jeske, Laurel E. Schock, Paul N. Swepston, Herbert Schumann, Tobin Jay Marks

Research output: Contribution to journalArticle

375 Scopus citations

Abstract

This contribution discusses lanthanide hydrocarbyl and hydride chemistry based upon Me2SiCp“2supporting ligation (Cp“ = 7/5-(CFf3 4C5). The reaction of MC13, M = Nd, Sm, or Lu, with Me2Si(Cp“Li)2yields the precursor complexes Me2SiCp”2MCl2 _Li(ether)2 +. A slightly different workup procedure yielded (Me2SiCp“2NdCl)2Cl“Li(THF)2 +, which crystallizes in the monoclinic space group P2/n with two molecules in a unit cell of dimensions (-133 °C) a = 11.666 (3) Å, b= 12.585 (3) Å, c = 17.765 (6) Å, and β = 94.91 (2)°. Least-squares refinement led to a value for the conventional R index (on F) of 0.045 for 3231 independent reflections having I > 3σ(I). The structure consists of two Me2Si(η5-Cp”)2Nd units bridged by a chloride ion and an Nd-Cl-.Li+.Cl-Nd linkage. The Nd-Cl distances are 2.802 (1) and 2.754 (2) Å, and ∠Cl-Nd-Cl = 97.1 (1)°. The (ring centroid)-Nd-(ring centroid) angle is 121.3°. The Nd-C(ring) distances vary from 2.647 (7) to 2.815 (7) A, with the shorter distances being to those carbon atoms closest to the Me2Si bridge. The Me2SiCp“2MCl2compounds react with LiCH[Si(CH3 3]2to yield ether- and halide-free Me2SiCp“2MCH[Si(CH3 3]2derivatives. The M = Nd compound crystallizes in the monoclinic space group P21/n with four molecules in a cell of dimensions (-125 °C) a = 10.229 (2) Å, b = 15.623 (3) Å, c = 19.687 (3) Å, and β = 105.41 (2)°. Least-squares refinement led to a value of the conventional R index (on F) of 0.044 for 3407 independent, absorption corrected reflections having I> 3σ(I). The molecular structure consists of monomeric Me2SiCp”2NdCH[Si(CH3 3]2units with η5-Cp“ coordination, and ∠(ring centroid)-Nd-(ring centroid) = 121.6°. The CH[Si(CH3 3]2fragment is coordinated to the Me2SiCp“2Nd center in a highly unsymmetrical fashion with a Nd-C σ-bond distance of 2.506 (7) Å and a secondary interaction to one methyl group of Nd-C = 2.862 (8) Å. The Si-C distance to this carbon atom is significantly longer than the other Si-CH3contacts. Approximate hydrogen atom locations argue against an important M—HC(methyl) interaction and reveal a bending of the hydrogen atom on the σ-bonded carbon atom toward the metal with ∠Nd-C-H ~ 76°. Reaction of the Me2SiCp“2MCH[Si(CH3 3]2complexes with H2yields the coresponding hydrides, which are formulated as Me2SiCp“2M(μ-H)2MCp“2SiMe2dimers. These compounds are active agents for the polymerization of ethylene as well as for the oligomerization of propylene and 1-hexene. For a constant lanthanide ion, a (Me2SiCp“2MH)2hydride is an ca. 10 times more active for this reaction than the corresponding (Cp'2MH)2hydride. Deprotonation of Me2SiCp”2LuCH(TMS)2with t-BuLi/TMEDA leads to a metallacycle formulated as Li(TMEDA)3 +-Me2SiCp“2LuCH2Si(CH3 2C(H)Si(CH2 3 -.

Original languageEnglish (US)
Pages (from-to)8103-8110
Number of pages8
JournalJournal of the American Chemical Society
Volume107
Issue number26
DOIs
StatePublished - Jan 1 1985

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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