期刊
ORGANOMETALLICS
卷 33, 期 24, 页码 7270-7278出版社
AMER CHEMICAL SOC
DOI: 10.1021/om501056b
关键词
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资金
- ANR [ANR 11-BS07-009-01]
- Engineering and Physical Sciences Research Council [EP/C534425/2, EP/C534425/1] Funding Source: researchfish
This article describes the generalization of an overlooked mechanism for CH bond activation at early transition metal centers, namely 1,3-CH bond addition at an eta(2)-alkene intermediate. The X-ray-characterized [Cp2Zr(c-C3H5)(2)] eliminates cyclopropane by a beta-H abstraction reaction to generate the transient eta(2)-cyclopropene [Cp2Zr(eta(2)-c-C3H4)] intermediate A. A rapidly cleaves the CH bond of furan and thiophene to give the furyl and thienyl complexes [Cp2Zr(c-C3H5)(2-C4H3X)] (X = O, S), respectively. Benzene is less cleanly activated. Mechanistic investigations including kinetic studies, isotope labeling, and DFT computation of the reaction profile all confirm that rapid stereospecific 1,3-CH bond addition across the Zr(eta(2)-alkene) bond of A follows the rate-determining beta-H abstraction reaction. DFT computations also suggest that an a-CC agostic rotamer of [Cp2Zr(c-C3H5)(2)] assists the beta-H abstraction of cyclopropane. The nature of the a-CC agostic interaction is discussed in the light of an NBO analysis.
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