Electronic structures of main-group carbene analogues.
Electronic structures of main-group carbene analogues.
复制标题
主族卡宾类似物的电子结构。
DOI：
10.1021/ic701350e
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发表时间：
2007
影响因子：
4.6
通讯作者：
P. Ragogna
中科院分区：
文献类型：
--
作者：
H. Tuononen;R. Roesler;J. Dutton;P. Ragogna
用量子化学方法对13-16族15个卡宾类似物的电子结构进行了分析，并与母体N-杂环卡宾（NHC）咪唑-2-亚基的电子结构进行了比较。本研究的结果提出了一个统一的分析的相似性和差异的电子结构的p-块主群卡宾类似物。虽然所有的系统形式上都是等价的，但理论分析明确地表明，它们的电子结构从C=C局域化（第13族）到C=N局域化（第16族），通过中间的，更离域的系统。特别是，锑离子和任何硫属离子都不是咪唑-2-亚基的直接类似物，因为它们都在二价主族中心周围含有两个孤对电子，而不是预期的电子。咪唑-2-亚基的主族类似物的电子结构的逐渐变化背后的原因被追踪到系统的总电荷，当在周期表中从左向右移动时，其从阴离子变为双阳离子。芳香性的理论分析结果表明，所有13-16族咪唑-2-亚基类似物都显示出一定程度的芳香性。较重的第13族阴离子从π-电子离域中受益最少，而阳离子第15族系统与母体碳系统相当，并且仅显示出比真正的6 π-电子芳族物质cyclohexenide略少的芳族特性。还评价了不同主族卡宾类似物的σ-供体和π-受体能力。
The electronic structures of 15 group 13-16 carbene analogues are analyzed using various quantum chemical methods and compared to the data obtained for the parent N-heterocyclic carbene (NHC), imidazol-2-ylidene. The results of this study present a uniform analysis of the similarities and differences in the electronic structures of p-block main-group carbene analogues. Though all systems are formally isovalent, the theoretical analyses unambiguously indicate that their electronic structures run the gamut from C=C localized (group 13) to C=N localized (group 16) via intermediate, more delocalized, systems. In particular, neither the stibenium ion nor any of the chalcogenium dications is a direct analogue of imidazol-2-ylidene as they all contain two lone pairs of electrons around the divalent main-group center, instead of the expected one. The reason behind the gradual change in the electronic structure of main-group analogues of imidazol-2-ylidene was traced to the total charge of the systems, which changes from anionic to dicationic when moving from left to right in the periodic table. Results from theoretical analyses of aromaticity show that all group 13-16 analogues of imidazol-2-ylidene display some degree of aromatic character. The heavier group 13 anions benefit the least from pi-electron delocalization, whereas the cationic group 15 systems are on par with the parent carbon system and display only slightly less aromatic character than cyclopentadienide, a true 6pi-electron aromatic species. The sigma-donor and pi-acceptor ability of the different main-group carbene analogues are also evaluated.