分子水素ピンチ:中性子 difraktion,NMR,および固体および溶液におけるデウテリウムラベリング研究による構造とメカニズム
Felix Schulz1, Victor Sumerin, Sami Heikkinen
1WACKER-Lehrstuhl für Makromolekulare Chemie, Technische Universität München, Lichtenbergstrasse 4, D-85747 Garching bei München, Germany.
Journal of the American Chemical Society
|November 18, 2011
まとめ
この研究では,アンサ-アミノボランによる可逆的な水素活性化が明らかになり,高度なスペクトロスコピ的方法を使用して,固体状態と溶液状態の両方で短い二水素結合を確認しました.
科学分野:
- 有機金属化学 有機金属化学
- 超分子化学 超分子化学
- スペクトル顕微鏡検査です.
背景:
- アンサ-アミノボランは,触媒の潜在的応用を持つ化合物のクラスです.
- それらの水素活性化メカニズムの理解は,新しい化学変換の開発に不可欠です.
- 研究された特定の化合物,1-N-TMPH-CH(2)-2-[HB(C(6) F(5))(2)]C(6) H(4) (NHHB) は,ユニークな分子ピンチ構造を特徴としています.
研究 の 目的:
- アンサ-アミノボランによる可逆水素活性化のメカニズムを解明する.
- 固体状態と溶液状態の両方でNHHBの構造的および動的性質を特徴付ける.
- 活性化プロセスにおける二水素結合の役割を調査する.
主な方法:
- 固体分析のための中性子 difraktion と thermogravimetric マススペクトロメトリー.
- 溶液状態の特徴化のための核磁気共振 (NMR) スペクトロスコーピー (T(1) リラクゼーション,1D NOE,変温,2D NOESYを含む).
- フーリエ変換赤外線 (FT-IR) スペクトロスコピーは,ダイナミックな相互作用を研究する.
- 同位体効果の研究のために,同位体的に標識された同位体 (NDDB,NHDB,NDHB) の合成.
- 実験的発見を裏付けるための理論的計算.
主要な成果:
- ニュートロン difraktionは,固体状態で短いN-H··H-B二水素結合 (1.67 Å) を確認しました.
- 溶液NMR研究では,類似のH-H距離 (1.6-1.8 Å) と,固体状態と溶液状態の構造的類似性が示されました.
- 同位体ラベリングは,二水素結合の存在を裏付ける主要な同位体効果を明らかにしました.
- FT-IRスペクトロスコピーは,室温でのダイナミックな分子内二水素結合の証拠を提供した.
- 初期移行状態に起因するデウテリウム水素活性化については,動的同位体効果は観察されなかった.
- 2D NOESY NMRは,アプロティック溶媒における素早い分子間陽子交換を示唆した.
結論:
- アンサ-アミノボランNHHBは,安定した分子内二水素結合を通じて,可逆的な水素活性化を促進します.
- 構造と水素結合の相互作用は,固体と溶液の相の間に保存されます.
- 運動同位体効果の欠如は,早期の移行状態を持つ容易な活性化プロセスを示唆する.
- 溶液では素早い分子間プロトン交換が起こり,触媒サイクルに関連する動的行動を示しています.
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