从环氧化物中催化O原子转移的动力学和机制
1Department of Chemistry, Oregon State University, Corvallis, Oregon 97331-4003, USA. gablek@chem.orst.edu
Journal of the American Chemical Society
|September 4, 2003
概括
环氧氧气原子转移到三酸,由Tp'ReO(3) 催化,涉及复杂的机制. 无论是孤立的还是现场生成的类物种都表现出高的催化效率,揭示了涉及直接原子转移和环氧环扩张的双重途径.
科学领域:
- 有机金属化学 有机金属化学
- 催化剂是一种催化剂.
- 反应机制 反应机制
背景情况:
- 氧复合物是氧原子转移反应的有效催化剂.
- 了解这些催化过程的复杂机制对于优化它们的效率至关重要.
研究的目的:
- 阐明氧原子从环氧化物转移到由Tp'ReO催化的三酸的复杂反应机制.
- 识别和描述参与催化循环的关键中间体.
- 为了研究不同反应路径之间的竞争.
主要方法:
- 光谱分析 (NMR,IR) 用于识别反应中间体.
- 动力学研究,以确定反应的顺序和速度.
- 含有的物种的隔离和特征.
- 竞争实验以区分拟议的路径.
主要成果:
- 减少Tp'ReO(3) 产生一种反应性物种,可能是Tp'ReO(2),它迅速形成可分离的Tp'Re(O) ((OH) (2) (1) 或Tp'Re(O) ((OEt) ((OH) (3).
- 催化剂1和3表现出与未净化的混合物相似的效率,复杂的动力学显示出最初的爆发,随后是伪零级的行为.
- 观察到一个 syn-Tp'Re ((O) ((diolate) 复合物,但仅仅它的循环逆转不能解释周转频率,这表明是一个协调的环氧化物中间体.
- 竞争实验表明,直接原子转移和环膨胀之间存在分离,其次是二酸盐循环逆转.
结论:
- 催化氧原子转移通过直接原子转移和环氧环膨胀途径的复杂相互作用进行.
- 一个协调的环氧化物中间体起着关键的作用,在这些竞争路线之间进行分区.
- 已识别的rhenium物种,包括二酸盐复合物,是催化系统的关键组成部分.
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