Intramolecular Cyclization of Ruthenium Vinylidene Complexes with a Tethering Vinyl Group: Facile Cleavage and Reconstruction of the C-C Double Bond

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• 作者：Cheng-Wei Cheng ; Yi-Chun Kuo ; Shu-Hao Chang ; Ying-Chih Lin ; Yi-Hong Liu ; Yu Wang
• 刊名：Journal of the American Chemical Society
• 出版年：2007
• 出版时间：December 5, 2007
• 年：2007
• 卷：129
• 期：48
• 页码：14974 - 14980
• 全文大小：148K
• 年卷期：v.129,no.48(December 5, 2007)
• ISSN：1520-5126

文摘

Protonation of ruthenium acetylide complexes [M]-*C*CCPh₂CH₂CH=CH₂ (2a, [M] = (⁵-C₅H₅)(P(OPh)₃)(PPh₃)Ru; 2a', [M] = (⁵-C₅H₅)(dppp)Ru; *C = ¹³C-labeled carbon atom) with HBF₄ in etherproduces [[M]=*C=CHCH₂CPh₂*CH=CH₂][BF₄] (4, 4') exclusively via a metathesis process of the terminalvinyl group with the *C=*C of the resulting vinylidene group. For 4 in methanol, bond reconstruction of thetwo labeled *C atoms readily takes place via a retro-metathesis process followed by a cyclization of theresulting vinylidene ligand giving the cyclic carbene complex 5, which is fully characterized by single-crystal X-ray diffraction analysis. The protonation of 2a in MeOH is followed by a cyclization, also giving 5.Deuterium-labeling study indicates that the C-C bond formation of this cyclization proceeds simultaneouslywith the formation of 4 consistent with facile cleavage and reconstruction of C=C bonds. For comparison,complex 4 in alcohol yields, besides 5, the corresponding alkoxycyclohexene 6. Formation of 6 from 4 alsoinvolves a skeletal rearrangement with reconstruction of the C=C bond. Interestingly, [[Ru']=*C=C(Me)CH₂CPh₂*CH=CH₂][BF₄] (8') originally from a complex with two connected labeled carbon atoms alsoundergoes reestablishment of the *C=*C bond yielding the cyclic allenyl complex 9'. ¹³C-labeling studiesclearly reveal the reestablishment of two C=C double bonds in the transformation of both 4 to 5 and 8' to9'. The proposed mechanism implicates a cyclobutylidene intermediate formed either via a regiospecific[2+2] cycloaddition of two double bonds in the ruthenium vinylidene 4 or via a cyclization of 4 giving anonclassical ion intermediate followed by a 1,2-alkyl shift.