Bonding modes in palladium(II) enolates:: Consequences for dynamic behavior and reactivity
Bonding modes in palladium(II) enolates:: Consequences for dynamic behavior and reactivity
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DOI：
10.1021/om990613o
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发表时间：
1999-12-20
期刊：
影响因子：
2.8
通讯作者：
Redón, R
中科院分区：
文献类型：
--
作者：
Albéniz, AC;Catalina, NM;Redón, R
本文研究了钯C键烯醇化物[Pd（CH_2C（O）CR_3）Cl（PPh_3）（2）]（R = H，1; R = Me，2）和[Pd（CH_2C（O）CR_3）（PPh_3）（2）（NCMe）]（BF_4）（R = H，5; R = Me，6）的行为。当金属上的配位位点可用时，在溶液中形成具有桥连烯醇化物部分的二聚体物质，所述配位位点具有Pd-2{μ-κ（2）-C，O-CH 2C（O）CR 3}（2）或具有混合的Pd-2{μ-κ（2）-C，O-CH 2C（O）CR 3}（μ-X）（X = Cl，OH）桥。提出π反馈对稳定氧带是重要的。配合物1和2在溶液中进行自由膦和配位膦之间的交换。动力学实验支持一个分子内的关联机制，这可能涉及一个oxoallyl-like过渡态。探讨了配合物的反应活性。研究了Pd-烷基化合物的一些典型反应，如CO插入生成CR_3C（O）CH_2COOH，对氧的亲电攻击是非常重要的：研究了烯醇化物配合物的水解以及与ClSiMe_3的反应生成甲硅烷基烯醇醚。
The behavior of palladium C-bound enolates [Pd(CH2C(O)CR3)Cl(PPh3)(2)] (R = H, 1; R = Me, 2) and [Pd(CH2C(O)CR3)(PPh3)(2)(NCMe)](BF4) (R = H, 5; R = Me, 6) has been studied. Dimeric-species with bridging enolate moieties are formed in solution when a coordination site on the metal is made available, either with Pd-2{mu-kappa(2)-C,O-CH2C(O)CR3}(2) or with mixed Pd-2{mu-kappa(2)-C, O-CH2C(O)CR3}(mu-X) (X = Cl, OH) bridges. It is proposed that pi back-donation is important to stabilize oxygen banding. Complexes 1 and 2 undergo exchange between free and coordinated phosphine in solution. Kinetic experiments support an intramolecular associative mechanism which could involve an oxoallyl-like transition state. The reactivity of the complexes has been explored. Some reactions typical of Pd-alkyls have been observed such as insertion of CO to give CR3C(O)CH2COOH, Electrophilic attack on oxygen is very important: the hydrolysis of the enolate complexes has been studied and also the reaction with ClSiMe3 to give silyl enol ethers.