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Please login to access the full content or check if you have access via Method 1: Synthesis of Bis(η5-cyclopentadienyl)diorganometal Complexes and Their Derivatives

DOI: 10.1055/sos-SD-002-00797

Negishi, E.-i.; Takahashi, T.Science of Synthesis, (20032710.

These compounds are generally prepared by the reaction of appropriate dihalo complexes with 2 equivalents of an organolithium or Grignard reagent. Organozincs may also be used in some cases, but organoaluminums can alkylate only once to give the corresponding bis(η5-cyclopentadienyl)halo(monoorgano)metal compounds. Dialkylbis(η5-cyclopentadienyl)zirconium and -hafnium complexes in which the alkyl groups contain one or more β-hydrogen atoms tend to be thermally unstable, and they decompose to give zirconacyclopropanes. As they significantly pertain to the chemistry of zirconacyclopropanes (Section 2.11.8) and zirconacyclopentanes (Section 2.11.5), and their hafnium analogues, they are mainly discussed in the sections indicated. In the absence of β-hydrogen atoms, dialkylbis(η5-cyclopentadienyl)zirconium and -hafnium complexes are relatively stable under thermal conditions. In contrast, their titanium counterparts can readily decompose via β-hydrogen abstraction. Some known and well-characterized bis(η5-cyclopentadienyl)diorganozirconium and -hafnium complexes are shown in Table 10.[‌139‌,‌197‌‌201‌]

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