陰離子鍵結之氮異環碳烯合成與結構分析及鋯金屬錯合物之研究

Abstract

[HC{(R)N(CHCH)N(CH2CH2NHtBu}]Br•HBr, R= MES (1-MES) 或 tBu (1-tBu) 加入過剩的氫氧化鈉得到化合物咪唑鹽類2， [HC{(R)N (CHCH)N(CH2CH2NHtBu}]Br.我們也用了立體障礙較大的2,6-diisopropylaniline去改變側邊臂上胺類基團，得到[2,6-(CH3)2(C6H3)]NHCH2CH2[HC{MESN(CHCH)N}]Br, (2-MES-Anil ian)。 由NaN(SiMe3)2可將咪唑鹽類2去氫化，而得到咪唑化合物3,由單晶X-Ray繞射分析得知咪唑化合物3-MES透過胺基以及咪唑上的碳(NCN)呈現出分子內彼此相互接觸的結果。 咪唑化合物3-tBu加入強鹼n-BuLi可得到穩定的金屬鋰咪唑化合物3-tBu.Li,此金屬鋰咪唑化合物為有效穩定高氧化態過渡金屬的轉移試劑，在加入ZrCl4即可得到產率不錯的ZrCl3-NHC, 7. 由X-Ray繞射得知咪唑化合物7為扭曲平面四面體的結構。 另外，3-MES與3-tBu分別與Zr(Bz)4反應，得到非常特別，具有aza-allyl及η2-N,C咪唑基團的金屬鋯化合物，6-MES和6-tBu。經由中間體5-MES 的結構分析以及動力學的研究，推斷出反應是經由C-H activation導致咪唑側邊臂上碳氮鍵斷裂，而此類型牽涉C-N鍵的斷裂以及在結構上文獻中是前所未有的。

Treatment of [HC{(R)N(CHCH)N(CH2CH2NHtBu}]Br•HBr, R = MES (1-MES) or tBu (1-tBu) with an excess of NaOH afforded the organic-soluble imidazolium salt 2,[HC{(R)N(CHCH)N(CH2CH2NH tBu}]Br. We also modified an alkyl of amino pendant arm group using bulkier 2,6-diisopropylaniline to afford the [2,6-(CH3)2(C6H3)] NHCH2CH2[HC{MESN(CHCH)N}]Br, (2-MES-Anilian). Deprotonation of imidazolium salt 2 by NaN(SiMe3)2 yielded the amino-linked free carbene, 3. The molecular structure of 3-MES was determined by X-ray single-crystal analysis, revealing an unexpectedly close intermolecular contact associated with the carbene and amine through an N-H • • • C interaction. Treatment of 3-tBu with n-BuLi gave the more stable Li carbene adduct 3-tBu.Li, which serves as an effective carbene transfer agent to stabilize high oxidation early transition metal and added the ZrCl4 to afford the ZrCl3-NHC, 7 in high yield. X-ray diffraction studies of ZrCl3-NHC confirmed the formation of distorted square planar Zr species, in which the NHC binds via conventional σ-donation of the lone pair to the electrophilic metal center. The reaction of Zr(Bz)4 with 3-MES with 3-tBu resulted to a unique meta-stable Zr complex, 6-MES and 6-tBu, possessing an aza-allyl and an η2-N,C-imidazolyl carbene moiety. The crystal structure of 5-MES exhibits an unexpected β-agostic interaction with kinetic investigation believed to involve C-H activation and unprecedented C-N cleavage of the amino-carbene moiety.