Liu Ming, Nieger Martin, Hübner Eike G, Schmidt Andreas
Clausthal University of Technology, Institute of Organic Chemistry, Leibnizstrasse 6, 38678, Clausthal-Zellerfeld, Germany), Fax: (+49)-5323-722834.
University of Helsinki, Laboratory of Inorganic Chemistry, Department of Chemistry, P.O. Box 55 (A.I. Virtasen aukio 1), 00014, Helsinki, Finland.
Chemistry. 2016 Apr 4;22(15):5416-24. doi: 10.1002/chem.201505042. Epub 2016 Mar 1.
2-(Imidazolium-1-yl)phenolates are conjugated heterocyclic mesomeric betaines in tautomeric equilibrium with the corresponding N-heterocyclic carbenes (NHCs), 3-(2-hydroxyphenyl)-imidazol-2-ylidenes. The carbene tautomers can be trapped as thiones (X-ray analysis). Moreover, bis(triphenylphosphine)palladium(II) dichloride in THF trapped the carbene tautomer as a palladium complex without participation of the phenolate group (X-ray analysis). The corresponding anionic NHCs, 2-phenolate-substituted imidazol-2-ylidenes, can be trapped by triethylborane or triphenylborane to form 4,4-diethyl- or 4,4-diphenyl-4H-benzo[e]imidazo[2,1-c][1,4,2]oxaza-borininium-4-ides, respectively (two X-ray analyses). These tricyclic systems are the first representatives of a new heterocyclic ring system. The results of DFT calculations concerning the HOMO/LUMO profiles and partial charges are also presented.
2-（咪唑-1-基）酚盐是与相应的N-杂环卡宾（NHC）处于互变异构平衡的共轭杂环中氮茚，即3-（2-羟基苯基）-咪唑-2-亚基。卡宾互变异构体可以作为硫酮被捕获（X射线分析）。此外，四氢呋喃中的二氯双（三苯基膦）钯（II）将卡宾互变异构体捕获为钯配合物，而酚盐基团未参与（X射线分析）。相应的阴离子NHC，即2-酚盐取代的咪唑-2-亚基，可以被三乙基硼烷或三苯基硼烷捕获，分别形成4,4-二乙基-或4,4-二苯基-4H-苯并[e]咪唑并[2,1-c][1,4,2]氧氮杂硼烷-4-亚胺（两次X射线分析）。这些三环体系是一种新的杂环体系的首批代表。还给出了关于最高占据分子轨道/最低未占据分子轨道轮廓和部分电荷的密度泛函理论计算结果。
