Boron–boron, carbon–carbon and nitrogen–nitrogen bonding in N-heterocyclic carbenes and their diazaboryl and triazole analogues: Wanzlick equilibrium revisited†,New Journal of Chemistry

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Boron–boron, carbon–carbon and nitrogen–nitrogen bonding in N-heterocyclic carbenes and their diazaboryl and triazole analogues: Wanzlick equilibrium revisited†
New Journal of Chemistry ( IF 2.7 ) Pub Date : 2018-03-16 00:00:00 , DOI: 10.1039/c8nj00296g
K. Młodzikowska _{1,

2,

3,

4} , A. A. Rajkiewicz _{1,

2,

3,

4} , K. Grela _{2,

4,

5,

6,

7} , B. Trzaskowski _{1,

2,

3,

4}

Affiliation

A series of monomers and dimers of N-heterocyclic carbenes and their diazaboryl and triazole analogues were investigated using the M06-2X and M06 density functional methods as well as using a DLPNO-CCSD(T) approach. We show that asymmetric carbenes bearing a benzyl and a mesityl moiety are predicted to form stable dimers due to favorable off-centre parallel stacking interactions. We also show that the double bond of the imidazole core destabilizes carbene dimers, shifting the Wanzlick equilibrium towards monomers. We predict that the methyl-, ethyl- and mesityl-substituted diazaboroles are more stable as monomers, irrespective of the presence of the double-bond in their structure, as are triazoles. Additionally, we demonstrate that the HOMO–LUMO gap difference between the monomer and the dimer, which is relatively easy to obtain, is a good indicator of the relative stability of the dimer versus the monomer for carbenes.

中文翻译：

N-杂环卡宾及其二氮杂硼烷基和三唑类似物中的硼-硼，碳-碳和氮-氮键：重新讨论了Wanzlick平衡†

使用M06-2X和M06密度泛函方法以及DLPNO-CCSD（T）方法研究了N-杂环卡宾的一系列单体和二聚体及其二氮杂硼烷基和三唑类似物。我们显示，由于有利的偏心平行堆积相互作用，预计带有苄基和异戊二烯部分的不对称碳烯形成稳定的二聚体。我们还显示，咪唑核心的双键使卡宾二聚体不稳定，将Wanzlick平衡移向单体。我们预测，甲基，乙基和异丁基取代的二氮杂硼烷作为单体更稳定，而与三唑一样，无论其结构中是否存在双键。此外，我们证明了相对容易获得的单体与二聚体之间的HOMO-LUMO间隙差异，而不是卡宾的单体。

更新日期：2018-03-16

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