从 (III) 化物中转移H-/H•/H+的动力学和热力学
1Department of Chemistry, Columbia University , New York, New York 10027, United States.
Journal of the American Chemical Society
|March 27, 2014
概括
这项研究研究了Rh-H键裂变在Rh(III) 化物复合体中,揭示它是一个高效的化物 (H-) 和基 (H•) 捐赠者,但是一个贫穷的质子 (H+) 捐赠者. 这些发现突出了其作为各种化学反应催化剂的潜力.
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:
- 化复合物在催化中至关重要,但它们的反应性,特别是Rh-H键的裂变模式,需要详细了解.
- 研究从Rh(III) 复合体中转移原子,质子和化物的热力学和动力学,可以了解它们的催化潜力.
研究的目的:
- 综合研究H(-),H(+) 和H•从Rh(III) 化物复合物Cp*Rh(2-(2-pyridyl) phenyl) H (1a) 中的裂变的热力学和动力学.
- 评估复合物1a在离子化中的催化效率及其作为原子供体的潜力.
主要方法:
- 热力学测量水性 (ΔG°H(-)) 通过H2的异质裂解.
- 对H(-) 转移到iminium和H(+) 转移到基的动力学研究.
- 通过H转移到TEMPO生成和表征一个Rh(II) 基中间体,并确定Rh-H键解离.
主要成果:
- 复合物1a表现出显著的热力学水性 (49.5(1) kcal/mol),并且由于快速的H(-) 转移 (kH(-) = 3.5(1) × 10(5) M(-1) s(-1)) 起到极高效的离子化催化剂的作用.
- 复合物1a是一个贫穷的H(+) 供体,无论是热力学 (pKa = 30.3(2)) 还是动力学 (kH(+) = 5(1) × 10(-4) M(-1) s(-1)).
- 复合物很容易转移H•形成稳定的Rh(II) 基,表明Rh-H键较弱 (58.2(3) kcal/mol) 和快速的H•转移动力学 (kH• = 1.17(3) × 10(3) M(-1) s(-1)).
结论:
- Cp*Rh(2-(2-pyridyl) phenyl) H (1a) 是一种多用途的试剂,作为一种优秀的H(-) 和H• 捐赠剂,但是一种贫穷的H(+) 捐赠剂.
- 观察到的反应性概况归因于对应的Rh (I) 离子的高能量.
- 这些发现支持复合1a在涉及转移的催化应用中的实用性.
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