アリルメチルフォスフォナートエステルのメカニズムと移行状態構造は,二重コーディネートされた二核コバルト ((III) センターに二重コーディネートされています
Guoqiang Feng1, Eric A Tanifum, Harry Adams
1University of Sheffield, Centre for Chemical Biology, Department of Chemistry, Sheffield, UK S3 7HF.
Journal of the American Chemical Society
|August 14, 2009
まとめ
この研究では,二核コバルト (III) コンプレックスとフォスフォン酸エステルの反応性を調べました. 発見は,酵素触媒に関連する水解機構と移行状態の洞察を明らかにします.
科学分野:
- * 無機化学 無機化学
- * バイオ・オーガニック・ケミストリー
- * 機械的有機化学について
背景:
- * リン酸エステルは,生物学的システムと化学合成において極めて重要です.
- * 二核コバルト (III) 複合体と1,4,7-トリアザサイクロノナン (TACN) リガンドは,酵素活性部位のモデルとして機能する.
- * フォスフォン酸エステルの水解を理解することは,反応機構を明らかにし,触媒を設計するための鍵です.
研究 の 目的:
- * 二核コバルト (III) 複合体への調整されたフォスフォン酸エステルの反応性および水解機構を調査する.
- * 複合フォスフォナートと非複合フォスフォナートの水解行動を比較する.
- * 塩基触媒化水解に関与する移行状態構造を解明する.
主な方法:
- * 5つの二核コバルト (III) -フォスフォン酸エステル複合体の合成と特徴付け.
- * 塩基触媒化水解の運動学的研究.
- * ブロンステッド選択性 (βlg) 値の決定.
- *様々な位置における運動同位体効果 (KIEs) の測定.
主要な成果:
- * フォスフォナートエステルの水解は,分子内酸化攻撃による特定の塩基触媒である.
- * 複合体 (-1.12) に対するブロンステッドのβlg値は,複合体でないフォスフォナート (-0.69) よりも著しくマイナスである.
- * KIEデータとβlg値は,ダイエステル水解ではなく,リン酸モノエステル水解に似た移行状態を示唆しています.
結論:
- * 二核コバルト (III) 複合体は,フォスフォン酸エステル水解を理解するための貴重なモデルを提供します.
- * 観察された反応性は,タンパク質フォスファタゼ-1. 1のような酵素における触媒機構に類似しています.
- *これらの発見は,新しい触媒の設計と生物学的水解過程の理解に貢献します.
関連する概念動画
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...
02:42Valence Bond Theory
Coordination compounds and complexes exhibit different colors, geometries, and magnetic behavior, depending on the metal atom/ion and ligands from which they are composed. In an attempt to explain the bonding and structure of coordination complexes, Linus Pauling proposed the valence bond theory, or VBT, using the concepts of hybridization and the overlapping of the atomic orbitals. According to VBT, the central metal atom or ion (Lewis acid) hybridizes to provide empty orbitals of suitable...
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...
02:52Stereoisomerism
Isomerism in Complexes
Isomers are different chemical species that have the same chemical formula.
Transition metal complexes often exist as geometric isomers, in which the same atoms are connected through the same types of bonds but with differences in their orientation in space. Coordination complexes with two different ligands in the cis and trans positions from a ligand of interest form isomers. For example, the octahedral [Co(NH3)4Cl2]+ ion has two isomers (Figure 1) In the cis...
Isomers are different chemical species that have the same chemical formula.
Transition metal complexes often exist as geometric isomers, in which the same atoms are connected through the same types of bonds but with differences in their orientation in space. Coordination complexes with two different ligands in the cis and trans positions from a ligand of interest form isomers. For example, the octahedral [Co(NH3)4Cl2]+ ion has two isomers (Figure 1) In the cis...
02:58Crystal Field Theory - Octahedral Complexes
Crystal Field Theory
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
02:54Coordination Compounds and Nomenclature
In most main group element compounds, the valence electrons of the isolated atoms combine to form chemical bonds that satisfy the octet rule. For instance, the four valence electrons of carbon overlap with electrons from four hydrogen atoms to form CH4. The one valence electron leaves sodium and adds to the seven valence electrons of chlorine to form the ionic formula unit NaCl (Figure 1a). Transition metals do not normally bond in this fashion. They primarily form coordinate covalent bonds, a...