Synthesis and Reactivity of Ruthenium Azido Complexes Containing a Hydridotris(pyrazolyl)borate Ligand and Dimerization of Terminal Alkynes in Organic and Aqueous Media

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• 作者：Chien-Kai Chen ; Hung-Chun Tong ; Chih-Yung Chen Hsu ; Chia-Yi Lee ; Yih Hsuan Fong ; Yao-Shun Chuang ; Yih-Hsing Lo ; Ying-Chih Lin ; Yu Wang
• 刊名：Organometallics
• 出版年：2009
• 出版时间：June 22, 2009
• 年：2009
• 卷：28
• 期：12
• 页码：3358-3368
• 全文大小：260K
• 年卷期：v.28,no.12(June 22, 2009)
• ISSN：1520-6041

文摘

Facile ligand substitution is observed when the ruthenium azido complex (PPh₃)[Ru]-N₃ (1; [Ru] = Tp(PPh₃)Ru) is treated with CH₃CN, yielding the nitrile-substituted ruthenium azido complex (CH₃CN)[Ru]-N₃ (2). Alkylation, [3 + 2] cycloaddition, and catalytic reactions of complex 2 have been investigated. In the case of [3 + 2] cycloaddition reactions, the metal-bound heterocyclic complexes (CH₃CN)[Ru]-N₃C₂(CO₂Me)₂ (3a), (CH₃CN)[Ru]-N₃C₂HCO₂Me (5), and (CH₃CN)[Ru]-N₃C₂HCN (6) are obtained from dimethyl acetylenedicarboxylate, methyl propiolate, and fumaronitrile, respectively. The tetrazolato complex [(CN)₂C═C(CN)₂][Ru]-N₄C[C(CN)═C(CN)₂] (8) is prepared from 2 and TCNE. Alkylation of 3a with organic bromides affords N-alkylated five-membered-ring organic triazoles. The reaction of CS₂ with 2 produces the thermally unstable thiothiatriazolate (CH₃CN)[Ru]-N₃CS(S) (10), which decomposes to the isothiocyanate (CH₃CN)[Ru]-NCS (11). On the other hand, several cationic imine complexes {(CH₃CN)[Ru]-(NH═CHR)}⁺ (12a, R = H; 12b, R = CH₃; 12c, R = HC═CH₂) are formed by the reaction of RCH₂X with the negatively charged nitrogen atom of the azido ligand on Ru^II. The reaction proceeds via formation of an alkylimido intermediate followed by N₂ evolution and proton transfer from the alkyl group to the imido nitrogen atom. Preliminary results on the catalytic activity of 2 are also presented. Interestingly, complex 2 catalyzes the dimerization of some terminal alkynes HC≡CR in organic and aqueous medium. Whereas with R = Ph, SiMe₃, t-Bu isomeric mixtures of head-to-head and head-to-tail coupling products are obtained, in the case of R = COOMe, E-selective head-to-head dimerization takes place exclusively. The structures of 1, 8, and 12c have been determined by X-ray diffraction analysis.