レドックス誘発による構造再編成 コバルトの動力学 (III) プロトン結合電子移転による水素形成
Daniel A Kurtz1, Debanjan Dhar1, Noémie Elgrishi1,2
1Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States.
Journal of the American Chemical Society
|February 23, 2021
まとめ
この研究は,陽子結合電子移転 (PCET) によるコバルト水素形成の複雑なメカニズムを示しています. リガンドの解離とステリック・バルクは,反応速度に大きな影響を及ぼし,より強い酸のプロトン移転定数にプラトウをもたらします.
科学分野:
- 有機金属化学
- 電気化学
- 反応メカニズム
背景:
- 2電子"陽子の反応は 化学的・生物学的過程において 極めて重要です
- 陽子結合電子移転 (PCET) は,酸化還元化学における重要なメカニズムである.
- PCETの運動に影響を与える要因を理解することは,触媒設計に不可欠です.
研究 の 目的:
- [CoCp (dxpe) (NCCH3) ]2+複合体の反応機構を明らかにし,水素種を形成する.
- 陽子移転速度の定数を定量化し,酸強度とリガンド構造への依存性を調査する.
- PCET運動の観測傾向に起因する要因を特定する.
主な方法:
- 酸の強度範囲 (22 pKa 単位) を用いたピークシフト分析によるサイクル電圧測定法.
- プロトネーション経路を追跡するためにデュテラート酸を使用する運動研究.
- 反応のステップと中間行動をモデル化するために,周期的なボルタムグラムのデジタルシミュレーション.
- ステリック効果を評価するために,ケラートするディフォスフィンリガンド (dppe,depe,dcpe) の体系的な変化.
主要な成果:
- 陽子移転速度の定数は,弱い酸の陽子源の強さと相関しているが,強い酸の強さは安定している.
- ディフォスフィン・リガンドのステリック・バルクは,観測された速度定数と逆相関し,よりボリュームの大きいリガンドはより遅い運動量を生成する.
- Cpリングにデウテリウムを組み込むことは,最初のリガンドプロトネーションを示し,その後にヒドリドへのタウトメリゼーションが続きます.
- デジタルシミュレーションでは,リダクションとプロトネーションのステップに先立つリガンド解離が示され,全体的なPCETプロセスはゲートされます.
結論:
- ハイドリド形成のメカニズムは,初期Co (III) 還元,アセトニトリルリガンド解離,Co (II) 還元からCo (I) 還元,Cpリングプロトン化,およびタウトメリゼーションを含む.
- フォスフィン・リガンドのステリック・バルクの影響を受けたリガンド分離均衡は,陽子の移転速度の観測された高原を制御する.
- この研究は,複雑なPCET反応を理解するために重要なダイナミックなリガンドの行動と基本的なステップを強調しています.
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