Development of novel NHO ligands for transition-metal catalysts

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K06456
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 47010:Pharmaceutical chemistry and drug development sciences-related
• Research Institution: Kumamoto University
• Principal Investigator: Ando Shin 熊本大学, 大学院生命科学研究部(薬), 助教 (00622599)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 配位子 / 炭素 / 遷移金属触媒

Outline of Final Research Achievements

N-heterocyclic olefin (NHO) ligands are alkylidene derivatives of NHCs that have emerged as highly electron-donative ligands over the past decade. Despite of their intriguing binding abilities of NHO ligands, reports of NHO-metal complexes remain limited. In this study, we synthesized a novel NHO that was equipped with a bicyclic framework. This 2-methyleneimidazolidine-based NHO was successfully applied to syntheses of Rh and Pd complexes, and the structures of the isolated complexes were confirmed via XRD and computational studies. Additionally, we found that [(NHO)PdCl2]2 complexes had a phosphine co-ligand that proved effective as a catalyst for Suzuki-Miyaura coupling at ambient temperature. By optimizing the N-substituents of NHO ligands and a phosphine co-ligand, we developed a [(NHO)Pd{[2-(CH3O)C6H4]3P}Cl2] complex as a catalyst that shows good catalytic activity.

Free Research Field

有機化学

Academic Significance and Societal Importance of the Research Achievements

望む化学変換に有効な金属触媒系を確立するには、配位子の電子供与性の調節が不可欠であり、その多様性の拡張は実現可能な化学反応の多様化につながる。本研究では、電子供与性が高いことが知られているものの、錯体合成等への応用が極限定的なNHOを基盤構造として用いた。独自に飽和型NHOを開発して種々検討した結果、その電子供与性は汎用されるNHC配位子よりも高く、既知の不飽和型NHOよりも低い、NHCと不飽和NHOの間の性質を示す配位子であることが分かった。独自にNHO-Pd錯体が触媒として機能する例も見出したことから、更なる検討によって新奇反応を実現し得る金属触媒の開発につながるものと期待する。