关于选择性氧化物N-N键裂变由三坐标 (III) 复合物的起源
J P Cherry1, A R Johnson, L M Baraldo
1Contribution from the Departments of Chemistry, Room 2-227, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307, USA.
Journal of the American Chemical Society
|July 27, 2001
概括
复合物与氧化发生反应,形成化和化产物,而不是预期的氧化复合物. 这种反应受到动力控制,这表明双金属N-N键裂变机制,受到连接体固体效应的影响.
科学领域:
- 有机金属化学 有机金属化学
- 无机化学 无机化学
- 反应机制 反应机制
背景情况:
- 已知含有大量氨基联体 (Mo(N[R]Ar) ((3)) 的复合物与氧转移试剂发生反应.
- 这些复合物与氧化 (N(2) O 的反应以前没有表征,预计将有氧转移.
研究的目的:
- 为了研究Mo(N[R]Ar)(3) 与N(2) O.O. 的反应途径.
- 为了确定控制这种反应的动力学和热力学参数.
- 阐明连接体在小分子激活中的固体性质的作用.
主要方法:
- 合成新的和复合物.
- 溶液热量计用于确定反应度.
- 停止流动的动力学研究,以分析反应速度和顺序.
- 竞争实验用于评估相对约束性亲缘关系.
主要成果:
- 在Mo(N[R]Ar) ((3) 与N(2) O的反应中,只能得到1:1的化物 (NMo(N[R]Ar) ((3)) 和化 (ONMo(N[R]Ar) ((3)) 复合物的混合物.
- 热量计提供了化复合物中Mo-N键解离值 (155.3 ± 3.3 kcal/mol) 的估计.
- 在Mo{N[R]Ar}{3}和N{2}O中,N{2}O反应是第一阶的,表明动力控制.
- 一个2 - 阿达曼提尔替代复合体显示了类似的反应性,但是~6倍慢,突出显示了固态效应.
- 竞争实验排除了N(2) O裂变机制中的氧化 (NO) 中介作用.
结论:
- 通过动力控制进行N(2) O反应,有利于化物和化的形成而不是氧转移.
- 后速率决定的双金属N-N键裂变机制是观察到的动力学和产品的最一致的解释.
- 体体质量对N(2) O激活的速度有显著影响,显示出对反应性的控制.
相关概念视频
Exceptions to the Octet Rule
Many covalent molecules have central atoms that do not have eight electrons in their Lewis structures. These molecules fall into three categories:
Coordination 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...
Coordination Number and Geometry
For transition metal complexes, the coordination number determines the geometry around the central metal ion. Table 1 compares coordination numbers to molecular geometry. The most common structures of the complexes in coordination compounds are octahedral, tetrahedral, and square planar.
Structural 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...
Valence 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...
Imperfections in Crystal Structure: Non-Stoichiometric Defects
Non-stoichiometric defects refer to a type of defect in the crystal structure of a compound where the ratio of its constituent elements deviates from the ideal stoichiometric ratio. There are two main types of non-stoichiometric defects: metal excess defects and metal deficiency defects.Metal excess defects occur when there is a slight surplus of metal ions than what is required by the stoichiometric ratio of the compound. For example, heating a sodium chloride crystal in sodium vapor results...


