Gas-Phase Energetics of Reductive Elimination from a Palladium(II) N-Heterocyclic Carbene Complex
Gas-Phase Energetics of Reductive Elimination from a Palladium(II) N-Heterocyclic Carbene Complex
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DOI：
10.1002/chem.200902929
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发表时间：
2010-01-01
影响因子：
4.3
通讯作者：
Chen, Peter
中科院分区：
文献类型：
--
作者：
Couzijn, Erik P. A.;Zocher, Eva;Chen, Peter
报道了苯基钯N-杂环卡宾（NHC）配合物的能量分辨碰撞诱导解离实验。NHC配体作为苯基咪唑离子的还原消除涉及30.9（14）kcal mol（-1）的势垒，而竞争性配体解离需要47.1（17）kcal mol（-1）。得到的三配位钯配合物易于进行还原C-C偶联得到苯基咪唑π配合物，其结合能为38.9（10）kcal mol（-1）。在M06-L//BP 86/TZP水平上的密度泛函理论计算与实验符合得很好。结合RRKM建模，这些结果表明，直接还原消除过程的速率决定步骤从C-C偶联步骤切换到低活化能下所得复合物的碎片化。
Energy-resolved collision-induced dissociation experiments using tandem mass spectrometry are reported for an phenylpalladium N-heterocyclic carbene (NHC) complex. Reductive elimination of an NHC ligand as a phenylimidazolium ion involves a barrier of 30.9(14) kcal mol(-1), whereas competitive ligand dissociation requires 47.1(17) kcal mol(-1). The resulting three-coordinate palladium complex readily undergoes reductive C-C coupling to give the phenylimidazolium pi complex, for which the binding energy was determined to be 38.9(10) kcal mol(-1). Density functional calculations at the M06-L//BP86/TZP level of theory are in very good agreement with experiment. In combination with RRKM modeling, these results suggest that the rate-determining step for the direct reductive elimination process switches from the C-C coupling step to the fragmentation of the resulting a complex at low activation energy.