Kinetic Data on the Synergetic Role of Amines and Water in the Reduction of Phosphine-Ligated Palladium(II) to Palladium(0)
Kinetic Data on the Synergetic Role of Amines and Water in the Reduction of Phosphine-Ligated Palladium(II) to Palladium(0)
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DOI：
10.1002/ejoc.201402519
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发表时间：
2014-08-01
影响因子：
2.8
通讯作者：
Romanov, Georgy
中科院分区：
文献类型：
--
作者：
Amatore, Christian;El Kaim, Laurent;Romanov, Georgy
叔胺如ETN(IPR)(2)不会将[PdCl2(PPh3)(2)]还原成Pd-0络合物。后者只有在加入水(生成HO-)后才形成，正如Grushin和Alper为NEt3所报告的那样。在过量PPh3存在的情况下，Pd-II/Pd-0还原反应的机理被用电化学技术定量地建立起来，该技术提供了[PdCl2(PPh3)(2)]消失和[Pd-0(PPh3)(3)]形成的动力学数据(测定平衡常数和速率常数)。生成了[PdCl(OH)(PPh3)(2)]，它允许OH与连接的PPh3之间的还原消除(PPh3的零级反应)，这导致了Pd-0络合物的形成。还原剂是连接的PPh3，最终生成(O)PPh3。整个还原过程的速度由施加HO-浓度的水量控制。
Tertiary amines such as EtN(iPr)(2) do not reduce [PdCl2(PPh3)(2)] into a Pd-0 complex. The latter is formed only after the addition of water (generation of HO-), as was reported by Grushin and Alper for NEt3. The mechanism of the Pd-II/Pd-0 reduction performed in the presence of an excess amount of PPh3 is established quantitatively by means of electrochemical techniques that provide kinetic data (determination of the equilibrium and rate constants) for the disappearance of [PdCl2(PPh3)(2)] and the formation of [Pd-0(PPh3)(3)]. [PdCl(OH)(PPh3)(2)] is formed, which allows reductive elimination between OH and the ligated PPh3 (zero-order reaction for PPh3), and this leads to a Pd-0 complex. The reducing agent is ligated PPh3, which ultimately yields (O)PPh3. The rate of the overall reduction process is controlled by the amount of water that imposes the concentration of HO-.