Ligand Electronic Effect on Reductive Elimination of Biphenyl from <i>ci</i>s-[Pt(Ph)<sub>2</sub>(diphosphine)] Complexes Bearing Electron-Poor Diphosphine: Correlation Study between Experimental and Theoretical Results
作者:Toshinobu Korenaga、Kayoko Abe、Aram Ko、Ryota Maenishi、Takashi Sakai
DOI:10.1021/om100073j
日期:2010.9.27
The reductive elimination of biphenyl from cis-[Pt(Ph)2(diphosphine)] (3) was studied to clarify the electronic effects of diphosphine ligands on the reaction. Reaction kinetic data were evaluated in d8-toluene within 80−110 °C using 1,2-bis(diphenylphosphino)ethane (dppe) and seven of its fluoroaromatic analogues as ancillary diphosphine ligands. The fastest reaction rate corresponded to 3, bearing
研究了从顺式-[Pt(Ph)2(diphosphine)](3)上还原性消除联苯,以阐明二膦配体对反应的电子作用。使用1,2-双(二苯基膦基)乙烷(dppe)及其七个氟代芳香族类似物作为辅助二膦配体,在80-110°C的d 8-甲苯中评估了反应动力学数据。最快的反应速率对应于3,带有贫电子的1,2-双[双(双(五氟苯基)膦基]乙烷(dfppe)配体,并且比带有dppe的3最慢,后者快1240倍。估计速率常数k与3中磷结合的芳族化合物的塔夫脱(Taft)σ*值高度相关。但是,它们之间的相关性被分为2,6-氟芳族化合物和带有2,6-氢芳族化合物的二膦,表明2,6-氟原子具有空间效应。所观察到的Δ ħ ⧧值与理论值,这是由DFT方法计算相关。相关性表明,贫电子的二膦配体减少了3的HOMO-1与过渡态3-TS(包括铂d轨道)的HOMO之间的能隙,并减少了与二膦结合时铂d轨道的不稳定。在3-TS与供