16および17エレクトロンの有機金属反応中介物に対するTEMPOの反応性:時間分解のIR研究
Justin P Lomont1, Son C Nguyen, Charles B Harris
1Department of Chemistry, University of California, Berkeley, Berkeley 94720, California, USA.
Journal of the American Chemical Society
|July 4, 2013
まとめ
(2,2,6,6-テトラメチルピペリジン-1-イール) オキシル基 (TEMPO) は,不飽和の有機金属中間体と反応する. TEMPOはアニオン結合体として作用し,結合メカニズムで協調し,金属の中心を酸化します.
科学分野:
- 有機金属化学 有機金属化学
- スペクトル顕微鏡検査です.
- コンピューティング・ケミストリー
背景:
- (2,2,6,6-テトラメチルピペリジン-1-イール) オキシル基 (TEMPO) は,触媒および生物学的研究において多用途である.
- TEMPOは,有機金属複合体のリガンドとして作用する際,多様な調整モードを現しています.
研究 の 目的:
- 協調不飽和の16および17電子の有機金属反応中間物とのTEMPOの反応性を調査する.
- メタルセンターへのTEMPO調整のメカニズムの特徴を述べる.
主な方法:
- 超高速の時間解像度の赤外線スペクトロスコーピーは,反応を監視します.
- 密度関数理論 (DFT) の計算でスペクトルを解釈し,構造を分析する.
主要な成果:
- TEMPOの座標は,結合メカニズムによって16電子 (CpCo(CO),Fe(CO) 4) と17電子 (CpFe(CO) 2,Mn(CO) 5) の種に変換されます.
- TEMPOアダクトは,TEMPOがピラミッド型の窒素幾何学を持つアニオンリガンドとして作用することを示しています.
- メタルセンターは,TEMPOの調整で酸化されます.
結論:
- この研究は,不飽和の有機金属複合体とのTEMPOの反応機構の最初の直接的な特徴付けを提供します.
- 結果は,一般的な反応中間物質とのTEMPOの相互作用に関する貴重な洞察を提供します.
- TEMPOの反応性は,研究された様々な低価移行金属複合体において一貫しています.
関連する概念動画
01:23Properties of Organometallic Compounds
Organometallic compounds are compounds that contain a carbon–metal bond. Carbon belongs to an organyl group like alkyl, aryl, allyl, or benzyl groups. The metal can be from Group I or Group II of the periodic table, a transition metal, or a semimetal.
01:11ortho–para-Directing Activators: –CH3, –OH, –NH2, –OCH3
All ortho–para directors, excluding halogens, are activating groups. These groups donate electrons to the ring, making the ring carbons electron-rich. Consequently, the reactivity of the aromatic ring towards electrophilic substitution increases. For instance, the nitration of anisole is about 10,000 times faster than the nitration of benzene. The electron-donating effect of the methoxy group in anisole activates the ortho and para positions on the ring and stabilizes the corresponding...
01:23Reactivity of Enolate Ions
Enolate ions are formed by the acid–base reaction of a carbonyl compound with a base. This leads to deprotonation of the α hydrogen atom, leading to a resonance-stabilized enolate ion where one of the contributing structures is an oxyanion, which imparts additional stability. Therefore, the proton on the α carbon is more acidic in nature than that of other sp3-hybridized C–H bonds but less acidic than those in O–H bonds where the negative charge in the conjugate base is localized on the oxygen...
01:20Radical Reactivity: Concentration Effects
In a radical reaction, the concentration of starting materials governs the selectivity of a radical. For example, the reaction between an alkyl halide and an alkene, in the presence of tin hydride and AIBN, begins with the generation of a tin radical. The generated radical then abstracts halogen from the alkyl halide, producing an alkyl radical. This alkyl radical can either react with tin hydride, yielding an alkane, or add to an alkene, generating a nitrile-stabilized radical, eventually...
02:46E1 Reaction: Kinetics and Mechanism
Here, in contrast to the E2 reaction mechanism, we delve into the aspects of the E1 reaction mechanism, which has two steps: rate-limiting loss of the leaving group and abstraction of the beta hydrogen by a weak base. Typically, the experimental proof for the E1 mechanism is via kinetic studies or isotope studies. While the former demonstrates the first-order kinetics—the dependence of the reaction solely on substrate concentration—the latter proves the abstraction of hydrogen only in the...
01:33Radical Reactivity: Intramolecular vs Intermolecular
Radical reactions can occur either intermolecularly or intramolecularly. In an intermolecular radical reaction, a nucleophilic radical adds to an electrophilic alkene or vice versa. In such reactions, the radical and generally the alkene, which is also called the radical trap, are two different molecules. Additionally, for such intermolecular reactions to occur, the radical trap must be active, present in an excess concentration, and the radical starting material must have a weak carbon–halogen...