Isolation and Reactivity of a Frustrated N-Heterocyclic Carbene-Borane

详细信息    查看全文

• 作者：Andrea Winkler ; Matthias Freytag ; Peter G. Jones and Matthias Tamm
• 刊名：Zeitschrift f蹲 anorganische und allgemeine Chemie
• 出版年：2016
• 出版时间：November 2016
• 年：2016
• 卷：642
• 期：22
• 页码：1295-1303
• 全文大小：283K
• ISSN：1521-3749

文摘

The synthesis of the frustrated carbene-borane 4-(9-borabicyclo[3.3.1]nona-9-yl)-1,3-di-tert-butylimidazolin-2-ylidene (6) was accomplished by deprotonation of the N-heterocyclic carbene (NHC) 1,3-di-tert-butylimidazolin-2-ylidene (1) at the 4-position with n-butyllithium, followed by addition of 9-chloro-9-borabicyclo[3.3.1]nonane (BBN-Cl). The abnormal carbene-borane adduct 5, with the BBN-Cl moiety at the 4-position, was obtained from the reaction of 1 with BBN-Cl; however, its conversion into 6 by treatment with K[N(SiMe₃)₂] (potassium hexamethyldisilazide, KHMDS) was not achieved. The reactions of 6 with the rhodium(I) complexes [Rh(COD)Cl]₂ (COD = 1,4-cyclooctadiene) and [Rh(CO)₂Cl]₂ afforded the complexes cis-[(6)Rh(COD)Cl] (7) and cis-[(6)Rh(CO)₂Cl] (8), with the latter allowing assessment of the σ-donor/π-acceptor properties of 6 by IR spectroscopy. The reactivity of 6 towards carbon dioxide, phenylacetylene and acetonitrile was studied, affording the labile adduct 6·CO₂ (9), whereas irreversible deprotonation and formation of the imidazolium phenylalkynylborate 10 and the imidazolium cyanomethylborate 11 was observed for PhCCH and CH₃CN. The molecular structures of 5, 7, 8, 10, and 11 were established by X-ray diffraction analyses.