Origin of Differences in Regioselectivity in the (Cyclo-) Polymerization of alpha, omega-Diynes and 1-Alkynes Between Tetra- and Penta-Coordinated Mo/W Imido/Oxo Alkylidene N-Heterocyclic Carbene Complexes and Implications for Ene-yne Metathesis

四配位和五配位Mo/W亚氨基/氧代亚烷基N-杂环卡宾配合物之间α、omega-二炔和1-炔烃的（环）聚合中区域选择性差异的起源及其对烯-炔复分解的影响

• 批准号: 449377332
• 负责人: Professor Dr. Michael R. Buchmeiser
• 金额: --
• 依托单位: Lehrstuhl für Makromolekulare Stoffe und Faserchemie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/449377332?language=en
• 关键词: Origin; Differences; Regioselectivity; Cyclo; Polymerization

The regioselectivity of olefin/alkyne metathesis reactions strongly depends on the structure and geometry of both, the pre-catalyst and the active species. In that regards, the questions, whether metathesis starts from and proceeds via pentacoordinated or tetracoordinated metal alkylidenes is of utmost importance. Since the regioselectivity in cyclopolymerization of diynes with pentacoordinated neutral and cationic metal imido alkylidene N-heterocyclic carbene (NHC) complexes differs substantially from the one of tetracoordinated, cationic ones, it is of high interest to reveal the origin of these differences in regioselectivity. For these purposes, we wish to study in detail the cyclopolymerization of alpha, omega-diynes as well as the polymerization of 1-alkynes using a tailored set of tetra- and pentacoordinated Mo/W imido/oxo alkylidene NHC complexes. Apart from the elucidation of the polymer structure in terms of cis/trans-content and structure of the repeat unit, these studies shall mainly focus on kinetic investigations to clarify whether either an associative or a dissociative mechanism is operative. Temperature-dependent NMR measurements of the rate constants will allow for additionally providing quantitative thermodynamic data on delta-S‡ at the transition state, which will provide unambiguous information about the molecularity of the process and thus about an associative or dissociative mechanism, respectively. Finally, these findings shall be correlated with those on the regio- and chemoselectivity in ene-yne metathesis catalyzed by the same set of (pre-) catalysts, again based on kinetic studies. The comprehensive picture that is to be generated will help for designing future, regioselective olefin and alkyne metathesis catalysts.

烯烃/炔复分解反应的区域选择性很大程度上取决于预催化剂和活性物质的结构和几何形状，在这方面，复分解是否从五配位或四配位金属亚烷基开始并进行是至关重要的。由于二炔与五配位中性和阳离子金属亚氨基亚烷基N-杂环环聚合的区域选择性卡宾（NHC）配合物与四配位阳离子配合物有很大不同，因此揭示这些区域选择性差异的根源非常有意义，出于这些目的，我们希望详细研究α，omega-二炔的环聚合。以及使用一组定制的四配位和五配位 Mo/W 亚氨基/氧代亚烷基 NHC 配合物进行 1-炔烃的聚合。为了阐明聚合物结构的顺式/反式含量和重复单元的结构，这些研究应主要集中在动力学研究上，以阐明缔合或解离机制是否适用于速率常数的温度依赖性核磁共振测量。将允许额外提供过渡态 delta-S‡ 的定量热力学数据，这将提供有关过程分子性的明确信息，从而提供有关缔合或解离的明确信息最后，这些发现应与同一组（前）催化剂催化的烯-炔复分解的区域选择性和化学选择性相关，同样基于动力学研究。产生的产物将有助于设计未来的区域选择性烯烃和炔复分解催化剂。