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化学学报
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化学学报 ›› 2009, Vol. 67 ›› Issue (6): 519-522. 上一篇    下一篇

研究论文

单氢钌配合物催化氢化苯乙烯的位阻效应

尹传奇* 冯权武 柏正武

  

  1. (武汉工程大学绿色化工过程省部共建教育部重点实验室 武汉 430074)

  • 投稿日期:2008-09-28 修回日期:2008-10-27 发布日期:2009-03-28
  • 通讯作者: 尹传奇

Steric Hindrance Effect on Hydrogenation of Styrene Catalyzed by Ruthenium Hydride Complex

Yin, Chuanqi* Feng, Quanwu Bai, Zhengwu

  

  1. (Key Laboratory for Green Chemical Process of Ministry of Education, Wuhan Institute of Technology, Wuhan 430074)
  • Received:2008-09-28 Revised:2008-10-27 Published:2009-03-28
  • Contact: YIN Chuan-Qi

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研究了溶剂分别为 THF, H2O/THF, CH3CN/THF以及ROH/THF (R＝Me, Et, iso-Pr, tert-Bu)条件下TpRuH(PPh3)- (CH3CN) [Tp＝hydrotris(pyrazolyl)borate]催化氢化苯乙烯生成乙基苯的反应, 发现向干燥THF体系中添加微量 H2O, CH3CN或ROH对催化反应都具有显著的促进作用. 催化机理研究表明, 小分子添加物首先取代TpRuH(PPh3)(CH3CN)中的PPh3配体形成中间体TpRuH(CH3CN)L (L＝H2O, CH3CN或ROH), 降低空间位阻, CH3CN配体随后被苯乙烯取代生成中间体 TpRuH(H2C＝CHPh)L; η2-苯乙烯插入Ru—H键后形成的Ru-烷基中间物与H2反应生成η2-H2配合物 TpRu(CH2CH2Ph)(H2)L或TpRu[CH(CH3)Ph](H2)L, 进而发生σ-复分解反应生成乙基苯完成催化循环.

关键词: 苯乙烯, 位阻, 催化氢化, 单氢钌配合物

Hydrogenation of styrene catalyzed by TpRuH(PPh3)(CH3CN) [Tp＝hydrotris(pyrazolyl)borate] with THF, H2O/THF, CH3CN/THF and ROH/THF (R＝Me, Et, iso-Pr, tert-Bu) as solvents was studied, respectively. It was found that addition of trace amount of small molecule H2O, CH3CN or ROH in anhydrous THF effectively promoted the catalytic reaction. The catalytic mechanism is proposed that PPh3 ligand in TpRuH(PPh3)(CH3CN) is first replaced by H2O, CH3CN or ROH to form intermediates TpRuH(CH3CN)L (L＝H2O, CH3CN or ROH) to reduce the steric hindrance of PPh3, and CH3CN is then replaced by styrene to produce TpRuH(H2C＝CHPh)L. The insertion of η2-styrene into the Ru—H bond followed by reaction with H2 leads to the formation of Ru-alkyl intermediates TpRu(CH2CH2Ph)(H2)L and TpRu[CH(CH3)Ph](H2)L. Intramolecular protonation of the adjacent alkyl ligand by an η2-H2 ligand produces ethylbenzene to fulfill the catalytic cycle.

Key words: styrene, steric hindrance, catalytic hydrogenation, ruthenium hydride complex

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