高度に選択的なFe-触媒化窒素を水素に固定する Sm ((II) 調整されたレドックスポテンシャルとpKaの反応剤によって可能
Emily A Boyd1, Jonas C Peters1
1Division of Chemistry and Chemical Engineering, California Institute of Technology (Caltech), Pasadena, California 91125, United States.
Journal of the American Chemical Society
|June 28, 2023
まとめ
研究者は,強いサマリウム還元剤を使用して,アンモニア (NH3) よりもヒドラジン (N2H4) を好み,窒素還元反応における製品選択性を制御した. この発見は,触媒性窒素固定に関する新しい洞察をもたらします.
科学分野:
- キャタリシス
- 無機化学
- 電気化学
背景:
- 小分子における多陽子,多電子の減少における製品選択性を制御することは,触媒化にとって極めて重要です.
- 窒素還元反応 (N2RR) のアンモニア (NH3) と水素 (N2H4) の選択性は十分に理解されていません.
- 鉄触媒は通常,N2RRでNH3の生成を好みます.
研究 の 目的:
- N2RRの選択性を反転させる条件を調査する.
- 鉄触媒を用いてアンモニア (NH3) よりもヒドラジン (N2H4) の生成を好む.
- N2RRにおける選択性制御のメカニズム的な基礎を理解する.
主な方法:
- トリス・フォスフィノ・ボランの鉄 (Fe) 触媒の選択性を逆転させる条件を開発した.
- 水素原子ドナーとしてヘクサデント酸ダイアニオンマクロサイクリックリガンド (Sm-PH) を有する,強く還元するSmII-(2-ピロリドン) コアを使用した.
- 反応経路を検知するために,スペクトロスコーピーを含む機械学的研究が採用された.
主要な成果:
- Sm-PHシステムで中程度の還元剤と強い酸を代用することで,独占的なN2H4生成 (>99:1) を達成した.
- 高い触媒活性と効率を維持し,Feあたり最大69%のN2H4と67%の固定N出力.
- NH3選択条件と比較して,N2H4生成のための700 mVの低余電位を観測した.
結論:
- N2H4は,開発された Sm 駆動条件下での運動産物です.
- 選択性は鉄水酸化物 (FeNNH2) によって決定される: プロトネーションはNH3を産生し,1電子の還元はN2H4を産生する.
- アニオンFeN2へのSmIII結合は,触媒の有効性に関与する可能性がある.
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