• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Chemistry: A European journal >The mechanism of the hydroalkoxycarbonylation of ethene and alkene-CO copolymerization catalyzed by Pd-II-diphosphine cations
【24h】

The mechanism of the hydroalkoxycarbonylation of ethene and alkene-CO copolymerization catalyzed by Pd-II-diphosphine cations

机译：Pd-II-二膦阳离子催化乙烯加氢烷氧羰基化反应机理及烯烃-CO共聚反应

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

All the intermediates in the "carboalkoxy" pathway, and their interconversions giving complete catalytic cycles, for palladium-diphosphine-catalyzed hydroalkoxycarbonylation of alkenes, and for alkene-CO copolymerization, have been demonstrated using P-31[H-1) and C-13[H-1] NMR spectroscopy. The propagation and termination steps of the "hydride" cycles and the crossover between the hydride and carboalkoxy cycles have also been demonstrated, providing the first examples of both cycles, and of chain crossover, being delineated for the same catalyst. Comparison of the propagation and termination steps in the pathways affords new insight into the selectivity-determining steps. Thus, reaction of [Pd(dibpp)(CH3CN)(2)](OTf)(2) (dibpp = 1,3- (iBu(2)p)(2)C3H6) with Et3N and CH3OH affords [Pd(dibpp)(OCH3)(CH3CN)]OTf, which, on exposure to CO, gives [Pd(dibpp)[C(O)OCH3] (CH3CN)]OTf immediately. Labeling studies show the reaction to be readily reversible. However, the back reaction is strongly inhibited by PPh3, indicating an insertion/deinsertion pathway. Ethene reacts with [Pd(dibpp)[C(O)OCH3](CH3CN)]OTf at 243 K to give [Pd(dibpp)[CH2CH2C(O)OCH3)]OTf, that is, there is no intrinsic barrier to alkene insertion into the PdC(O)OMe bond, as had been pro-posed. Instead, termination is proposed to be selectivity determining. Methanolysis of the acyl intermediate [Pd(dibpp)(C(O)CH3)L]X (L = CO, CH3OH; X = CF3SO3- (OTf-), CH3C6H4SO3- (OTs-)) is required in the hydride cycle to give an ester and occurs at 243 K on the timescale of minutes, whereas methanolysis of the P chelate, required to give an ester from the carbomethoxy cycle, is slow on a timescale of days, at 298 K. These results suggest that slow methanolysis of the P chelate, rather than slow insertion of an alkene into the Pd-carboalkoxy bond, as had previously been proposed, is responsible for the dominance of the hydride mechanism in hydroalkoxycarbonylation.
机译：使用P-31 [H-1）和C-已证明了“羰基烷氧基”途径中的所有中间体及其相互转化提供了完整的催化循环，用于钯-二膦催化的烯烃的氢烷氧羰基化以及烯烃-CO的共聚。 13 [H-1] NMR光谱。还已经证明了“氢化物”循环的传播和终止步骤以及氢化物和碳烷氧基循环之间的交换，提供了针对同一催化剂的两个循环以及链交换的第一个实例。途径中传播和终止步骤的比较为选择性决定步骤提供了新的见识。因此，[Pd（dibpp）（CH3CN）（2）]（OTf）（2）（dibpp = 1,3-（iBu（2）p）（2）C3H6）与Et3N和CH3OH的反应得到[Pd（dibpp ）（OCH3）（CH3CN）] OTf，当暴露于CO时，立即产生[Pd（dibpp）[C（O）OCH3]（CH3CN）] OTf。标记研究表明该反应易于逆转。但是，PPh3强烈抑制了反应，表明存在插入/插入途径。乙烯在243 K下与[Pd（dibpp）[C（O）OCH3]（CH3CN）] OTf反应得到[Pd（dibpp）[CH2CH2C（O）OCH3）] OTf，即，烯烃没有内在的障碍提议将其插入PdC（O）OMe键。相反，提出终止是选择性确定。在氢化物循环中需要酰基中间体[Pd（dibpp）（C（O）CH3）L] X（L = CO，CH3OH; X = CF3SO3-（OTf-），CH3C6H4SO3-（OTs-））的甲醇分解反应生成酯并在243 K上以分钟为单位发生，而从碳氧甲氧基循环生成酯所需的P螯合物的甲醇分解在几天内以298 K的速度缓慢。这些结果表明， P螯合物不是如先前已经提出的将烯烃缓慢插入Pd-羰基烷氧基键中的原因，而是导致氢化烷氧基羰基化中氢化机理的主导。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号