メタルロセネ触媒によるプロピレンポリメリゼーション中のチェーンエピメリゼーション:ダブルラベルプロピレンを使用した機械学的研究
Jeffrey C Yoder1, John E Bercaw
1Arnold and Mabel Beckman Laboratories of Chemical Synthesis, California Institute of Technology, Pasadena, CA 91125, USA.
Journal of the American Chemical Society
|March 14, 2002
まとめ
プロピレンポリメリゼーションにおけるチェーンエピメリゼーションは,同位体ラベル付きプロピレンを用いて研究されました. この発見は,アリル/二水素複合体を除くβ-Dの除去と挿入を含むメカニズムを示唆している.
科学分野:
- ポリマー化学のポリマー化学について
- 有機金属化学 有機金属化学
- スペクトル顕微鏡検査です.
背景:
- メタルロセンの触媒を用いたプロピレンポリメリゼーションは,ポリオレフィン生産に不可欠です.
- チェーンエピメリゼーションの仕組みを理解することは,ポリマー立体化学を制御する鍵です.
- rac- ((EBTHI) ZrCl ((2) と rac- ((EBI) ZrCl ((2) のような同型特異的触媒は,典型的には非常にステレオレギュラーなポリプロピレンを生成する.
研究 の 目的:
- プロピレンポリメリゼーション中のチェーンエピメリゼーションの詳細なメカニズムを解明する.
- ステレオ化学的誤差における特定の中間物質の役割を調査する.
- 同位体ラベリングを使用して提案されたエピメリゼーション経路を区別する.
主な方法:
- 同位体でラベル付けされたプロピレンの合成 (CH(2)=CD(13) CH(3)).
- メチラルミノキサンで活性化されたrac-(EBTHI) ZrCl(2) およびrac-(EBI) ZrCl(2) 触媒を用いたプロピレンポリメリゼーション.
- 炭素13核磁気共振 ((13) C NMR) スペクトロスコーピーを用いてポリマーマイクロ構造の分析.
主要な成果:
- チェーンエピメリゼーションに起因するステレオエラーは,プロピレン濃度が低く,温度が適度な場合に観察されました.
- (13)C NMRは,様々なペンタドおよびヘプタド配列内の特定の (13)Cラベル付きメチレングループおよび同位体単位 ([CD(13) CH(3) ], [CH(13) CH(3) ]を明らかにした.
- 観察された誤差は,β-Dの除去,オレフィン回転,エナンチオファシアル相互変換,および第三アルキル中間体への挿入を含むメカニズムと一致し,逆のステップが続く.
結論:
- この研究は,これらのメタロゼン触媒によるポリメリゼーションにおける特定の鎖エピメリゼーション機構の有力な証拠を提供します.
- 特定のペンタドの特定の標識単位 ([CH(2) CH(13) CH(2) D-) の欠如は,媒介種としてアリル/二水素複合体を排除する.
- この詳細なメカニズムの理解は,ポリプロピレンのステレオ規則性に対する制御を改善するための触媒の設計に役立ちます.
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