A DFT Study of the Effect of the Ligands in the Reductive Elimination from Palladium Bis(allyl) Complexes
A DFT Study of the Effect of the Ligands in the Reductive Elimination from Palladium Bis(allyl) Complexes
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DOI：
10.1021/om1001974
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发表时间：
2010-05
期刊：
影响因子：
2.8
通讯作者：
M. Pérez-Rodríguez;A. Braga;A. Lera;F. Maseras;R. Álvarez;P. Espinet
中科院分区：
文献类型：
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作者：
M. Pérez-Rodríguez;A. Braga;A. Lera;F. Maseras;R. Álvarez;P. Espinet
用密度泛函方法研究了某些配体(L=空、PMe3、乙烯、顺丁烯二酸酐)对顺式-[Pd(η1-烯丙基)(η1-烯丙基)(PMe3)L]和Pd(η1-烯丙基)(η3-烯丙基)L生成六-1，5-二烯的还原消除作用。在各种可能的偶联过程(C1sp3−C1‘sp3、C3sp2−C3’sp2和C1sp3−C3‘sp2)中，C3−C3’键的形成在所有情况下都是最受欢迎的，正如以前报道的顺式-[Pd(η1-烯丙基)(η1-烯丙基)(Ph3)2]。有趣的是，这种偶联反应的活化能随着L配体的变化而变化：空的(4.6kcal/mol)<；MA(5.8kcal/mol)<；CH2CH2(12.5kcal/mol)<；PMe3(17.3kcal/mol)。因此，三配位的Pd(η1-烯丙基)(η1-烯丙基)L配合物的还原消除速率比四配位的要高。对于通过直接的C_1-−C_1‘还原消除偶联的碳配体(烷基、芳基、烯基)，L=空<；L=MA的顺序是相反的；L=空<；L=MA的顺序也跟随着烯丙基。
The effect of some selected ligands (L = empty, PMe3, ethylene, maleic anhydride) in the reductive elimination of the palladium complexes cis-[Pd(η1-allyl)(η1-allyl)(PMe3)L] and Pd(η1-allyl)(η3-allyl)L to form hexa-1,5-diene was computationally studied using DFT methods. Among the various possible coupling processes (C1sp3−C1′sp3, C3sp2−C3′sp2, and C1sp3−C3′sp2), C3−C3′ bond formation is the most favored in all cases, as reported before for cis-[Pd(η1-allyl)(η1-allyl)(PH3)2]. Interestingly, the activation energy for this coupling changes with the L ligand: empty (4.6 kcal/mol) < MA (5.8 kcal/mol) < CH2CH2 (12.5 kcal/mol) < PMe3 (17.3 kcal/mol). Therefore, tricoordinated Pd(η1-allyl)(η1-allyl)L complexes undergo reductive elimination at higher rates than the tetracoordinated counterparts. The order L = empty < L = MA is inverse to that found for carbon ligands (alkyl, aryl, alkenyl) that couple via direct C1−C1′ reductive elimination; the order L = empty < L = MA is also followed by the allyl groups when t...