イリジウムピンサー複合体における二水素の温度および溶媒に依存する結合
Inigo Göttker-Schnetmann1, D Michael Heinekey, Maurice Brookhart
1Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3290, USA.
Journal of the American Chemical Society
|December 21, 2006
まとめ
デュテリウムラベル付きのイリジウム複合体は,温度および溶媒に依存する行動を示します. 同位体シフトと結合定数は,延長された二水素リガンドを示唆し,これは水素と二水素構造を均衡させるモデルによって説明されます.
科学分野:
- 有機金属化学 有機金属化学
- 無機化学 無機化学とは
- スペクトロスコーピーは,スペクトロスコーピーを用います.
背景:
- イリジウム複合体とヒドリドリガンドは,触媒作用において極めて重要です.
- リガンドのダイナミクスと結合を理解することは,反応機構の鍵です.
- デウテリウムラベリングは,水素リガンドの行動に関する洞察を提供します.
研究 の 目的:
- デウテリウムラベル付イリジウム複合体を合成し,特徴づけること.
- 温度と溶媒がリガンド構造に及ぼす影響を調査する.
- H2リガンドとヒドリド環境の性質を明らかにする.
主な方法:
- デウテリウムラベル付き (p-XPOCOP) IrH2-xD_x複合体の合成.
- 1Hおよび2D NMRを用いた光譜分析.
- 変数温度と溶媒に関する研究.
- 核スピン格子リラクゼーションの測定 (T1 (min))
主要な成果:
- 観測された有意な温度と溶剤依存の同位体シフトとHDカップリング定数 (JHD).
- 非極性溶媒 (トルーエン,ペンタン) での長方形のH2リガンドの証拠.
- 複合体6−d1は,塩素溶媒でJHD=0Hzを示し,温度に依存する大きな同位体効果を示した.
- これらの影響は,ヒドリド環境の非統計的占有に起因する.
結論:
- 実験データは,2つの構成要素のモデルをサポートしています.
- 溶解したIr (III) 二酸化水素とIr (I) 二酸化水素の種間の急速な均衡が提案されています.
- この動的均衡は,観測された温度と溶媒依存現象を説明する.
さらに関連する動画
関連する概念動画
02:37Types of Chemical Bonds
Chemical bonding theories were pioneered by American chemist Gilbert N. Lewis. He developed a model called the Lewis model to explain the type and formation of different bonds. Chemical bonding is central to chemistry; it explains how atoms or ions bond together to form molecules. It explains why some bonds are strong and others are weak, or why one carbon bonds with two oxygens and not three; why water is H2O and not H4O.
02:55Temperature Dependence on Reaction Rate
The Collision Theory
Atoms, molecules, or ions must collide before they can react with each other. Atoms must be close together to form chemical bonds. This premise is the basis for a theory that explains many observations regarding chemical kinetics, including factors affecting reaction rates.
The collision theory is based on the postulates that (i) the reaction rate is proportional to the rate of reactant collisions, (ii) the reacting species collide in an orientation allowing contact between...
Atoms, molecules, or ions must collide before they can react with each other. Atoms must be close together to form chemical bonds. This premise is the basis for a theory that explains many observations regarding chemical kinetics, including factors affecting reaction rates.
The collision theory is based on the postulates that (i) the reaction rate is proportional to the rate of reactant collisions, (ii) the reacting species collide in an orientation allowing contact between...
02:51Metal-Ligand Bonds
The hemoglobin in the blood, the chlorophyll in green plants, vitamin B-12, and the catalyst used in the manufacture of polyethylene all contain coordination compounds. Ions of the metals, especially the transition metals, are likely to form complexes.
In these complexes, transition metals form coordinate covalent bonds, a kind of Lewis acid-base interaction in which both of the electrons in the bond are contributed by a donor (Lewis base) to an electron acceptor (Lewis acid). The Lewis acid in...
In these complexes, transition metals form coordinate covalent bonds, a kind of Lewis acid-base interaction in which both of the electrons in the bond are contributed by a donor (Lewis base) to an electron acceptor (Lewis acid). The Lewis acid in...
02:34Structural Isomerism
Isomerism in Complexes
Isomers are different chemical species that have the same chemical formula. Structural isomerism of coordination compounds can be divided into two subcategories, the linkage isomers and coordination-sphere isomers.
Linkage isomers occur when the coordination compound contains a ligand that can bind to the transition metal center through two different atoms. For example, the CN− ligand can bind through the carbon atom or through the nitrogen atom. Similarly, SCN− can be...
Isomers are different chemical species that have the same chemical formula. Structural isomerism of coordination compounds can be divided into two subcategories, the linkage isomers and coordination-sphere isomers.
Linkage isomers occur when the coordination compound contains a ligand that can bind to the transition metal center through two different atoms. For example, the CN− ligand can bind through the carbon atom or through the nitrogen atom. Similarly, SCN− can be...
01:09Complexation Equilibria: Factors Influencing Stability of Complexes
In complexation reactions, metal cations are the electron pair acceptors, and the ligands are the electron pair donors. The stability of the metal complexes depends primarily on the complexing ability of the central metal ion and the nature of the ligands. Generally, the complexing ability of the metal ion depends on the size and charge of the ion. As the metal ion size increases, the stability of the metal complexes decreases, provided that the valency of the metal ion and the ligands remain...
00:43Complexometric Titration: Ligands
Different monodentate and polydentate ligands are used as complexing agents in complexometric titration reactions. The formation of complexes by mono- and bidentate ligands involves two or more intermediate steps, limiting their use as complexing agents. In comparison, polydentate ligands can form complexes with metal ions in a single-step process, facilitating sharper end points. This means polydentate ligands, such as amino carboxylic acid derivatives, are most commonly employed in...