Identification of the effective palladium(0) catalytic species generated in situ from mixtures of Pd(dba)(2) and bidentate phosphine ligands. Determination of their rates and mechanism in oxidative addition
Identification of the effective palladium(0) catalytic species generated in situ from mixtures of Pd(dba)(2) and bidentate phosphine ligands. Determination of their rates and mechanism in oxidative addition
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DOI：
10.1021/ja9637098
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发表时间：
1997-06-04
影响因子：
15
通讯作者：
Khalil, F
中科院分区：
文献类型：
--
作者：
Amatore, C;Broeker, G;Khalil, F
Pd(Dba)(2)+2L-L(其中L-L是双齿配体，如dppm、dppe、dppp、dppb、dppf和diop)的混合物导致Pd(L-L)(2)的配合物的形成，该配合物不与碘苯氧化加成。Pd(Dba)(2)+2BINAP的混合物不是Pd(BINAP)(2)，而是Pd(Dba)(BINAP)。Pd(Dba)(2)+1L-L(L-L=dppm，dppe，dppp，dppb，dppf，diop，和binap)的混合物可在短时间内形成Pd(Dba)(L-L)络合物，但dppf和binap直接形成络合物Pd(Dba)(L-L)除外。Pd(DBA)(L-L)是溶液中的主要络合物，但与连接较少的Pd(L-L)和DBA处于能量平衡状态。Pd(L-L)是苯碘氧化加成反应中活性较强的物种。然而，钯(Dba)(L-L)也与苯碘发生平行反应。从这些不同催化体系与苯碘的氧化加成反应的动力学数据中，可以观察到反应的顺序如下：Pd(Dba)(2)+1DIOP>；Pd(Dba)(2)+1dppf>；>；Pd(Dba)(2)+1BINAP。所有这些与一个双齿配体相关的体系都比Pd(Dba)(2)+2PPh(3)的反应活性低。
Mixtures of Pd(dba)(2) + 2L-L (where L-L is a bidentate ligand such as dppm, dppe, dppp, dppb, dppf, and DIOP) lead to the formation of Pd(L-L)(2) complexes which do not undergo an oxidative addition with phenyl iodide. Mixtures of Pd(dba)(2) + 2 BINAP do not afford Pd(BINAP)(2) but Pd(dba)(BINAP). Mixtures of Pd(dba)(2) + 1L-L (L-L = dppm, dppe, dppp, dppb, dppf, DIOP, and BINAP) lead to Pd(dba)(L-L) complexes via the formation, at short time, of the complex Pd(L-L)(2), except for dppf and BINAP where the complex Pd(dba)(L-L) is directly formed. Pd(dba)(L-L) is the main complex in solution but is involved in an endergonic equilibrium with the less ligated complex Pd(L-L) and dba. Pd(L-L) is the more reactive species in the oxidative addition with phenyl iodide. However, Pd(dba)(L-L) also reacts in parallel with phenyl iodide. From the kinetic data concerning the reactivity of these different catalytic systems in the oxidative addition with phenyl iodide, one observes the following order of reactivity: Pd(dba)(2) + 1DIOP > Pd(dba)(2) + 1dppf >> Pd(dba)(2) + 1BINAP. All these systems associated to one bidentate ligand are less reactive than Pd(dba)(2) + 2PPh(3).