結晶状態におけるCo-C結合の割れ方のX線分析
1Laboratory of Chemistry for Natural Products, Tokyo Institute of Technology, Japan.
Nature
|May 12, 1977
まとめ
コバロキシム結晶をX線分析したところ,単位細胞の寸法がゆっくり変化していることが示されました. この構造的シフトは,非対称な水素化研究中にシアノエチルグループのレース化に関連していた.
科学分野:
- 有機金属化学 有機金属化学
- クリスタログラフィーです.
- カタリシス カタリシス カタリシス
背景:
- コバロキシム誘導体は,非対称な水素化における触媒特性のために研究されています.
- これらの複合体の構造的動態を理解することは,それらの触媒機構の解釈に極めて重要です.
研究 の 目的:
- X線曝露時にR-アルファ-シアノエチル (S-アルファ-メチルベンジラミン) -コバラキシム結晶の構造変化を調査する.
- 観察された構造変化と,非対称な水素化におけるコバルキシム誘導体の触媒能力を相関させる.
主な方法:
- コバロキシム誘導体の単一結晶のX線 difrraction分析を連続的に実施した.
- 構造変化の様々な中間段階において,強度データを収集した.
- 構造的進化を分析するために,各段階の電子密度計算が行われました.
主要な成果:
- R-alpha-cyanoethyl (S-alpha-methylbenzylamine) -cobaloximeの結晶は,X線曝露下で単位細胞の寸法の変化を示した.
- これらの構造の変化はゆっくりと発生し,複数の中間段階でのデータ収集を可能にしました.
- 計算された電子密度は,観測された変化がシアノエチルグループのラセミゼーションと一致することを確認しました.
結論:
- X線曝露は,コバルキシム結晶内のシアノエチル群のゆっくりとしたラセミゼーションを誘発する.
- 観察された構造の変化は,触媒過程中のコバルキシム誘導体の動的行動に関する洞察を提供します.
- この発見は,非対称的水素化における構造と触媒活動の関係に関するより深い理解に貢献します.
さらに関連する動画
08:44Measurements of Long-range Electronic Correlations During Femtosecond Diffraction Experiments Performed on Nanocrystals of Buckminsterfullerene
Published on: August 22, 2017
08:55Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses
Published on: June 7, 2018
関連する概念動画
02:18X-ray Crystallography
The size of the unit cell and the arrangement of atoms in a crystal may be determined from measurements of the diffraction of X-rays by the crystal, termed X-ray crystallography.
Diffraction
Diffraction is the change in the direction of travel experienced by an electromagnetic wave when it encounters a physical barrier whose dimensions are comparable to those of the wavelength of the light. X-rays are electromagnetic radiation with wavelengths about as long as the distance between neighboring...
Diffraction
Diffraction is the change in the direction of travel experienced by an electromagnetic wave when it encounters a physical barrier whose dimensions are comparable to those of the wavelength of the light. X-rays are electromagnetic radiation with wavelengths about as long as the distance between neighboring...
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...
02:46Crystal Field Theory - Tetrahedral and Square Planar Complexes
Tetrahedral Complexes
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
00:57C–C Bond Cleavage: Retro-Aldol Reaction
The reverse of the aldol addition reaction is called the retro-aldol reaction. Here, the carbon–carbon bond in the aldol product is cleaved under acidic or basic conditions to form two molecules of carbonyl compounds. The mechanism of the reaction consists of three steps.
In the first step, as depicted in Figure 1, the base deprotonates the β-hydroxy ketone at the hydroxyl group to form an alkoxide ion.
In the first step, as depicted in Figure 1, the base deprotonates the β-hydroxy ketone at the hydroxyl group to form an alkoxide ion.
01:10X-ray Diffraction of Biological Samples
X-ray diffraction or XRD is an analytical tool that utilizes X-rays to study ordered structures such as crystalline organic and inorganic samples, polycrystalline materials, proteins, carbohydrates, and drugs.
According to Bragg's law, when X-rays strike the sample positioned on a stage, the rays are scattered by the electron clouds around the sample atoms. The X-ray diffraction or scattering is caused by constructive interference of the X-ray waves that reflect off the internal crystal...
According to Bragg's law, when X-rays strike the sample positioned on a stage, the rays are scattered by the electron clouds around the sample atoms. The X-ray diffraction or scattering is caused by constructive interference of the X-ray waves that reflect off the internal crystal...
01:29Determination of Crystal Structures
In the late 1800s, the revelation that light extended beyond visible wavelengths led to the discovery of X-rays by Wilhelm Roentgen. Recognized as high-energy electromagnetic radiation with short wavelengths, X-rays prompted exploration into their interaction with crystals. Max von Laue proposed in 1912 that the periodic arrangement of atoms, ions, or molecules in crystals would cause them to diffract X-rays, a hypothesis confirmed through experiments with copper sulfate and zinc sulfide...