...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Exploring the acid-catalyzed substitution mechanism of [Fe4S4Cl4](2-)
【24h】

Exploring the acid-catalyzed substitution mechanism of [Fe4S4Cl4](2-)

机译：探索[Fe4S4Cl4]（2-）的酸催化取代机理

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Kinetic studies on the acid-catalyzed substitution reactions of the teminal chloro-ligands in [Fe4S4Cl4](2-) by PhS- in the presence of the acids NHR3+ (R = Me, Pr-n or Bu-n) are reported. Although these acids have very similar pK(a)s (17.6-18.4) the reactions show a variety of different kinetics, some of which are inconsistent with a mechanism involving simple protonation of the cluster followed by substitution of a terminal ligand. The observed behaviour is more consistent with the recently proposed mechanism in which Fe-(mu(3)-SH) bond elongation/cleavage occurs upon protonation of a mu(3)-S, and suggests that both the acidity and bulk of the acid is important in the protonation step. Other studies have determined the activation parameters (Delta H-double dagger and Delta S-double dagger) for both the protonation and substitution steps of the acid-catalyzed substitution reactions of [Fe4S4X4](2-) (X = Cl or SEt). A significantly negative Delta S-double dagger is observed for the substitution steps of both clusters indicating associative pathways. This is inconsistent with earlier interpretation of the kinetics of these reactions (based exclusively on the dependence of the rate on the concentration of nucleophile) and indicates that there is no dissociative substitution mechanism and the pathway associated with a zero order dependence on the concentration of PhS-involves associative substitution with the solvent (MeCN) being the nucleophile.
机译：报告了在酸NHR3 +（R = Me，Pr-n或Bu-n）存在下，PhS-对[Fe4S4Cl4]（2-）中末端氯配体进行酸催化取代反应的动力学研究。尽管这些酸具有非常相似的pK（a）（17.6-18.4），但反应显示出各种不同的动力学，其中一些与涉及簇的简单质子化然后取代末端配体的机理不一致。观察到的行为与最近提出的机制更一致，在该机制中，在mu（3）-S质子化时会发生Fe-（mu（3）-SH）键延伸/断裂，并且表明酸的酸度和体积在质子化步骤中很重要其他研究已经确定了[Fe4S4X4]（2-）（X = Cl或SEt）的酸催化取代反应的质子化和取代步骤的活化参数（ΔH双刀和ΔS双刀）。在两个簇的取代步骤中观察到显着负的Delta S-双匕首，表明缔合途径。这与这些反应动力学的早期解释不一致（仅基于速率对亲核试剂浓度的依赖性），并且表明不存在解离性取代机理，且与零序依赖性对PhS浓度相关的途径-涉及与作为亲核试剂的溶剂（MeCN）的缔合取代。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号