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Please login to access the full content or check if you have access via2.11.4.4.3 Method 3: By Carbometalation
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Negishi, E.-i.; Takahashi, T., Science of Synthesis, (2003) 2, 707.
Carbometalation converts one organometallic complex into another containing the same metal (e.g., see Scheme 1). It is, in principle, applicable to the synthesis of monoalkyl- and monoalkenylbis(η5-cyclopentadienyl)metal complexes. In reality, the scope of carbozirconation as a method for the synthesis of discrete chlorobis(η5-cyclopentadienyl)monoorganozirconium compounds is rather limited for various reasons: Firstly, carbozirconation must be a process of higher activation energy than the corresponding hydrozirconation reaction. It normally requires either a bimetallic reagent system consisting of zirconium and aluminum compounds, or strained zirconacycles, including zirconacyclopropanes. The latter leads to the formation of five-membered zirconacycles discussed in Section 2.11.5. In the former reaction involving zirconium–aluminum reagents, the carbozirconation products are usually converted into organoaluminum compounds. Therefore, back-transmetalation from aluminum to zirconium is necessary to obtain organozirconium derivatives, as shown in Scheme 26. The in situ transmetalation from zirconium to aluminum can be exploited in developing zirconium-catalyzed carboalumination reactions, as discussed in Sections 2.11.4.7.6.1 and 2.11.4.7.6.2. For these reasons, the current scope of discrete carbozirconation to give bis(η5-cyclopentadienyl)monoorganozirconium complexes is rather limited, even though it is believed to occur widely in zirconium-catalyzed carbometalation reactions including the Ziegler–Natta polymerization.[469] The reaction of alkynylaluminum 62 with chlorobis(η5-cyclopentadienyl)methylzirconium(IV) (51) to give the monoorganozirconium compound 63 (Scheme 27)[126] is a prototypical example of carbozirconation producing discrete organozirconium derivatives.
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References
| [126] | Meeeeee, M.; Meeeeee, M., M. Me. Meee. Mee., (8888) 888, 8888. |
| [469] | Meeeeeeeee Meeee Meeeeeeee Meeeeeeeeeeeeee: Meeeeee–Meeee eee Meeeeeeeee Meeeeeeeeeeeeee, Meeee, M. M., Me.; Meeeeeeee Meeeeeeeee Meeee: Meeeeeeee, MM, (8888). |
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- 8.Meeeee-Meee, (8888) M 88-8, 888.
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