• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Chemistry: A European journal >Unprecedented ROMP Activity of Low-Valent Rhenium-Nitrosyl Complexes:Mechanistic Evaluation of an Electrophilic Olefin Metathesis System
【24h】

Unprecedented ROMP Activity of Low-Valent Rhenium-Nitrosyl Complexes:Mechanistic Evaluation of an Electrophilic Olefin Metathesis System

机译：低价hen-亚硝酰基配合物空前的ROMP活性：亲电子烯烃复分解系统的机械评估。

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

The reaction of [Re(H)(NO)_2(PR_3)_2] complexes (la:R=PCy_3;1b:R=PiPr_3) with [H(OEt_2)_2][BAr_4~F] ([BAr_4~F]=tetra-kis{3,5-bis(trifluoromethyl)phenyl}bo-rate) in benzene at room temperature gave the corresponding cations [Re(NO)_2(PR_3)_2][BAr_4~F] (2a and 2b).The addition of phenyldiazomethane to benzene solutions of 2a and 2b afforded the moderately stable cationic rhe-nium(I)-benzylidene-dinitrosyl-bis(tri-alkyl)phosphine complexes 3a and 3b as [BAr_4~F]~- salts in good yields.The complexes 2 a and 2b catalyze the ring-opening metathesis polymerization (ROMP) of highly strained nonfunc-tionalized cyclic olefins to give polymers with relatively high polydispersity indices,high molecular weights and over 80% Z configuration of the double bonds in the chain backbone.However,these complexes do not show metathesis activity with acyclic olefins.The benzylidene derivatives 3 a and 3b are almost inactive in ROMP catalysis with norbornene and in olefin metathesis.NMR experiments gave the first hints of the initial formation of carbene complexes from [Re(NO)_2(PR_3)_2]-[BAr_4~F] (2a and 2b) and norbornene.In a detailed mechanistic study ESI-MS/MS measurements provided further evidence that the carbene formation is initiated by a unique reaction sequence where the cleavage of the strained ole-finic bond starts with phosphine migration forming a cyclic ylide-carbene complex,capable of undergoing metathesis with alternating rhenacyclobu-tane formation and cycloreversion reactions ("ylide" route).However,even at an early stage the ROMP propagation route is expected to merge into an "iminate" route by attack by the ylide function on one of the N_(NO) atoms followed by phosphine oxide elimination.The formation of phosphine oxide was confirmed by NMR spectroscopy.The proposed mechanism is supported further by detailed DFT calculations.
机译：[Re（H）（NO）_2（PR_3）_2]配合物（la：R = PCy_3; 1b：R = PiPr_3）与[H（OEt_2）_2] [BAr_4〜F]（[BAr_4〜F]室温下在苯中的＝四-基{3，5-双（三氟甲基）苯基}硼酸酯）得到相应的阳离子[Re（NO）_2（PR_3）_2] [BAr_4〜F]（2a和2b）。将苯基重氮甲烷添加到2a和2b的苯溶液中，得到具有中等收率的适度稳定的阳离子铑（I）-亚苄基-二亚硝酰基-双（三烷基）膦配合物3a和3b，为[BAr_4〜F]〜-盐。配合物2a和2b催化高度应变的非官能化环烯烃的开环复分解聚合（ROMP），以提供具有相对高的多分散指数，高分子量和链中双键的Z构型超过80％的聚合物然而，这些配合物对无环烯烃不具有复分解活性。亚苄基衍生物3a和3b在降冰片烯的ROMP催化和烯烃复分解中几乎没有活性。NMR实验给出了从[Re（NO）_2（PR_3）_2]-[BAr_4〜F]（2a和2b）和降冰片烯初步形成卡宾络合物的初步提示。在详细的机理研究中，ESI-MS / MS测量提供了进一步的证据卡宾的形成是由独特的反应序列引发的，在该反应序列中，断裂的烯烃-finic键的裂解始于膦的迁移，形成环状的叶立德-卡宾配合物，该化合物能够通过交替的丁二烯环戊烷生成和环还原反应进行复分解反应（“叶立德”路线） ）。然而，即使在早期，ROMP的传播途径仍有望通过对N_（NO）原子之一上的叶立德函数的攻击而合并成“亚胺化”途径，然后消除氧化膦。拟议的机理进一步得到了详细的DFT计算的支持。

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