Stirling András
Theoretical Chemistry Research Group, Institute of Organic Chemistry, Research Centre for Natural Sciences, Budapest, Hungary.
Chemistry. 2018 Feb 1;24(7):1709-1713. doi: 10.1002/chem.201705285. Epub 2017 Dec 28.
The so-called hypervalent iodane compounds are very useful and versatile reactants and oxidizing agents in modern organic chemistry. The hypercoordinated central iodine in these compounds hints at a hypervalent state, which is often stressed to justify their reactivity. In this study a theoretical analysis of the electronic structure of a large, representative set of hypercoordinated iodane compounds has been carried out. We observed that the iodonium is not hypervalent in these compounds. In contrast, the analysis reveals a variation of the iodine valence state from a normal octet state to hypovalent depending on the ligands, but irrespective of the coordination number. On the basis of the calculations the reactivity of these compounds can be ascribed to the strong unquenched charge separation present in these molecules which represents a compromise between Coulomb interaction and the resistance of iodonium toward hypervalency. In extreme cases this leads to hypovalency and enhanced reactivity.
所谓的高价碘烷化合物在现代有机化学中是非常有用且用途广泛的反应物和氧化剂。这些化合物中具有超配位的中心碘暗示着一种高价态，人们常常强调这一点来解释它们的反应活性。在本研究中，我们对一大组具有代表性的超配位碘烷化合物的电子结构进行了理论分析。我们观察到这些化合物中的碘鎓并非高价态。相反，分析表明，根据配体的不同，碘的价态会从正常的八隅体状态变化到低价态，而与配位数无关。基于计算结果，这些化合物的反应活性可归因于这些分子中存在的强烈未淬灭电荷分离，这代表了库仑相互作用与碘鎓对高价态的抗性之间的一种平衡。在极端情况下，这会导致低价态并增强反应活性。
