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Formation of NH,NR N‐Heterocyclic Carbene Complexes through Mercuration of Mono‐ N ‐substituted Benzimidazoles
Author(s) -
Yu MingHung,
Yang HsuehHui,
Naziruddin Abbas Raja,
Kanne Shanker,
Wang BoHan,
Liu FuChen,
Lin Ivan J. B.,
Lee GeneHsiang
Publication year - 2016
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201600759
Subject(s) - chemistry , carbene , protonation , deprotonation , benzimidazole , medicinal chemistry , ion , stereochemistry , organic chemistry , catalysis
A simple two‐step method to prepare NH,NR N‐heterocyclic carbene (NHC) complexes is described herein. In the first step, the reactions of N ‐substituted benzimidazoles (R‐BimH) with Hg(OAc) 2 in the presence of NaBr rendered 12‐membered mercuramacrocycles [Hg 4 (R‐Bim) 4 Br 4 ] [R = Me, pyridyl (Py), Bn]. These complexes consist of four Hg II ions bridged by four benzimidazolyl anions through N and C atoms. This reaction presumably proceeds through an initial N‐complexation of the benzimidazole to the Hg II ion. Consequently, C2‐H becomes more acidic, and even an acetate anion can promote the deprotonation at C2 to form the C‐metalated products. The second step involves the protonation of these mercuramacrocycles with HBF 4 · OEt 2 to give the protic complexes featuring the NH,NR–NHC ligands of general formula [(R‐BimH) 2 Hg][BF 4 ] 2 (R = Me, Py, Bn).