Manipulation of Organoactinide Coordinative Unsaturation. Synthesis, Structures, and Reactivity of Thorium Hydrocarbyls and Hydrides with Chelating Bis(tetramethylcyclopentadienyl) Ancillary Ligands

Carol M. Fendrick, Larry D. Schertz, Tobin J. Marks, Victor W. Day

Research output: Contribution to journalArticle

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Abstract

This contribution describes thorium hydrocarbyl and hydride chemistry based upon the chelating (CH3)2Si[(CH3)4C5]22-ligand (Me2SiCp“22~). Precursor Me2Si(Cp“H)2 can be prepared by reaction of SiCl4with 2 equiv of Li(CH3)4C5, followed by methylation (CH3Li) and methanolic workup. Subsequent reaction with n-C4HgLi in 1, 2-dimethoxyethane yields Me2Si(CpLi)2-2DME. The dilithium salt undergoes reaction with ThCl4to yield Me2SiCp”2ThCl2-2LiCl.2DME, which, in turn, can be alkylated with lithium reagents to produce crystalline, thermally stable Me2SiCp2ThR2complexes where R = CH2Si(CH3)3, CH2C(CH3)3, C6H6, M-c4H9, and CHoC6H5. The Me2SiCp”2Th[CH2Si(CH3)3]2 complex crystallizes in the monoclinic space group P21/m—C2/lwith two molecules in a unit cell of dimensions (20 ± 1 °C) a = 11.960 (5) Å, b = 11.270 (5) Å, c = 12.395 (6) Å, and β= 99.32 (4)°. Least-squares refinement led to a value for the conventional R index (on F) of 0.076 for 2586 independent reflections having I > 3σ(I). The molecular structure consists of monomeric Me2SiCp”2Th[CH2Si(CH3)3]2 units with η5-Cp” coordination and ∠(ring centroid)-Th-(ring centroid) = 118.4°. There is considerable dispersion in the Th-C(ring) distances. The Th[CH2Si(CH3)3]2 ligation is highly distorted, with Th-C-Si angles of 123.7 (14)° and 149.5 (12)°, accompanied by corresponding Th-C distances of 2.54 (2) and 2.48 (2) A, respectively. The thorium coordination sphere is more “open” than that in Cp'2Th[CH2Si(CH3)3]2. Hydrogenolysis of the dialkyl yields the dimeric hydride Me2SiCp''2Th(M-H)4ThCp“2SiMe2, which crystallizes in the monoclinic space group P21/n with four molecules in a unit cell of dimensions (20 ± 1 °C) a = 10.965 (2) Å, b = 19.843 (5) Å, c = 18.759 (3) Å, and β = 90.39 (2)°. Least-squares refinement led to a value for the conventional R index (on F) of 0.075 for 3298 independent reflections having I > 3σ(I). The dimer exhibits approximate C2symmetry with (ring centroid)-Th-(ring centroid) angles of 118.1° and 117.7°. The Th-Th distance is 3.632 (2) A which suggests, in combination with infrared spectral data, a Th(μ-H)4Th structure. The above hydride catalyzes the hydrogenation of 1-hexene at a rate ca. 103 faster than (Cp'2ThH2)2. For trans-2-hexene, hydrogenation catalyzed by the ring-bridged hydride is ca. 30 times more rapid than by (Cp2'ThH2)2.

Original languageEnglish
Pages (from-to)1828-1838
Number of pages11
JournalOrganometallics
Volume7
Issue number8
DOIs
Publication statusPublished - Aug 1988

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry

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