18 electron rule

简明释义

18 电子则

英英释义

例句

1.When designing new catalysts, chemists often refer to the 18 electron rule (18电子规则) to predict reactivity.

在设计新催化剂时，化学家通常参考18电子规则（18电子规则）来预测反应性。

2.The 18 electron rule (18电子规则) helps in understanding why certain metal complexes are more stable than others.

通过18电子规则（18电子规则），我们可以理解为什么某些金属配合物比其他配合物更稳定。

3.Many students learn about the 18 electron rule (18电子规则) in their inorganic chemistry courses.

许多学生在无机化学课程中学习18电子规则（18电子规则）。

4.The stability of many transition metal complexes can be explained using the 18 electron rule (18电子规则).

许多过渡金属配合物的稳定性可以用18电子规则（18电子规则）来解释。

5.In organometallic chemistry, the 18 electron rule (18电子规则) is a crucial guideline for predicting the structure of complexes.

在有机金属化学中，18电子规则（18电子规则）是预测配合物结构的重要指导原则。

作文

The 18 electron rule is a fundamental concept in the field of coordination chemistry and organometallic chemistry. It serves as a guideline to predict the stability and reactivity of metal complexes. This rule states that stable transition metal complexes tend to have a total of 18 valence electrons, which is the same electron count as that of the noble gas configuration. The significance of the 18 electron rule lies in its ability to simplify the understanding of complex structures and their bonding characteristics.To understand the 18 electron rule, it is essential to recognize the role of transition metals in forming complexes. Transition metals have partially filled d-orbitals, which allow them to form various types of bonds with ligands. Ligands are molecules or ions that can donate electron pairs to the metal, thereby stabilizing the complex. The electron count for a metal complex is obtained by adding the electrons contributed by the metal and those donated by the ligands.For instance, consider a typical transition metal complex such as [Fe(CO)6]. In this complex, iron (Fe) contributes 8 valence electrons, while each carbon monoxide (CO) ligand donates 2 electrons. Since there are six CO ligands, they contribute a total of 12 electrons. Adding these together gives us a total of 20 electrons, which exceeds the 18 electron rule. However, this complex is still stable due to the strong field strength of CO as a ligand, which stabilizes the complex despite the higher electron count.On the other hand, a complex like [Ni(CN)4] adheres more closely to the 18 electron rule. Nickel (Ni) contributes 10 electrons, and each cyanide (CN) ligand donates 2 electrons. With four CN ligands, the total contribution from the ligands is 8 electrons, leading to a total of 18 electrons. This adherence to the 18 electron rule suggests that the complex is likely to be stable and less reactive compared to those that exceed this electron count.The 18 electron rule is not an absolute law; there are exceptions where complexes with fewer or more than 18 electrons can still be stable. These exceptions often arise due to factors such as steric hindrance, electronic effects, and the nature of the ligands involved. For example, some complexes can stabilize themselves through strong metal-ligand interactions or through the presence of π-acceptor ligands that can participate in back-bonding.In addition to predicting stability, the 18 electron rule also provides insight into the reactivity of metal complexes. Complexes that adhere closely to this rule are generally less reactive because they are already in a stable electron configuration. Conversely, complexes that deviate significantly from the 18 electron rule may exhibit increased reactivity as they seek to achieve a more stable electron arrangement.In conclusion, the 18 electron rule is a valuable tool for chemists working with transition metal complexes. It offers a framework for predicting the stability and reactivity of these complexes, aiding in the design of new materials and catalysts. While there are exceptions to this rule, its general applicability makes it an essential concept in understanding the behavior of metal complexes in coordination and organometallic chemistry. As research continues in this field, the 18 electron rule will undoubtedly remain a cornerstone of our understanding of metal-ligand interactions and complex stability.

“18电子规则”是配位化学和有机金属化学领域的一个基本概念。它作为一种指导原则，用于预测金属配合物的稳定性和反应性。该规则指出，稳定的过渡金属配合物往往具有总计18个价电子，这与惰性气体的电子构型相同。“18电子规则”的重要性在于它能够简化对复杂结构及其键合特性的理解。要理解“18电子规则”，必须认识到过渡金属在形成配合物中的作用。过渡金属具有部分填充的d轨道，这使它们能够与配体形成各种类型的键。配体是可以向金属捐赠电子对的分子或离子，从而稳定配合物。金属配合物的电子计数是通过将金属贡献的电子数与配体捐赠的电子数相加得出的。例如，考虑一个典型的过渡金属配合物[Fe(CO)6]。在这个配合物中，铁（Fe）贡献8个价电子，而每个一氧化碳（CO）配体捐赠2个电子。由于有六个CO配体，它们总共贡献12个电子。将这些相加，我们得到20个电子，这超过了“18电子规则”。然而，由于CO作为配体的强场强度，即使电子计数较高，该配合物仍然是稳定的。另一方面，像[Ni(CN)4]这样的配合物则更接近“18电子规则”。镍（Ni）贡献10个电子，而每个氰化物（CN）配体捐赠2个电子。四个CN配体的总贡献为8个电子，总计18个电子。这种遵循“18电子规则”的现象表明，该配合物可能是稳定的，并且比那些超出此电子计数的配合物反应性低。“18电子规则”并不是绝对的法则；有些配合物的电子数少于或多于18也能保持稳定。这些例外通常是由于空间位阻、电子效应以及所涉及的配体性质等因素造成的。例如，一些配合物可以通过强金属-配体相互作用或通过存在π-受体配体参与反向配位来稳定自己。除了预测稳定性外，“18电子规则”还提供了关于金属配合物反应性的见解。那些紧密遵循这一规则的配合物通常反应性较低，因为它们已经处于稳定的电子构型。相反，显著偏离“18电子规则”的配合物可能表现出更高的反应性，因为它们寻求达到更稳定的电子排列。总之，“18电子规则”是化学家在研究过渡金属配合物时的重要工具。它为预测这些配合物的稳定性和反应性提供了框架，有助于设计新材料和催化剂。尽管该规则有例外，但其普遍适用性使其成为理解金属配合物在配位和有机金属化学中行为的基本概念。随着该领域研究的持续进行，“18电子规则”无疑将继续成为我们理解金属-配体相互作用和配合物稳定性的基石。