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Issue 5, 2017
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Structural diversities in Ag(i) complexes of xylyl platform based isomeric bis-NHC ligands: effects of pyridine wingtip substituents

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Abstract

Pyridine is employed as a wingtip substituent for the preparation of xylyl platform based bis-NHC ligands to investigate its effect on the formation of Ag(I)–NHC complexes. Hence, three new ligands L1L3 are synthesized as their imidazolium salts H2(L1L3)(PF6)2 by 2 : 1 reaction of 2-(1H-imidazole-1-yl)pyridine with ortho-, meta- and para-bis(bromomethyl)benzene followed by anion exchange. Treatment of these imidazolium salts with 2 equivalents of Ag2O generates Ag(I)–NHC complexes with diverse structural motifs. Ligand L1 generates a metallo-macrocycle (1) via dimeric assembly of the ligand through Ag(I) coordination. Interestingly, these dimeric assemblies are further connected through C(sp3)–H⋯C(sp2) hydrogen bonding interactions which thereby construct an infinite 1D polymer of metallo-macrocycles. In the presence of Ag(I), L2 generates metallo-macrocycle 2 that is connected via Ag(I)⋯Ag(I) interactions. Noticeably, in this polymeric arrangement, Ag(I) ions are arranged almost in a linear fashion with bond angles of 177.95° in an Ag3 unit. In the presence of Ag(I), ligand L3 generates an open chain 1D polymer (3), where the two substituents on the benzene ring are in a transoid position and the C–Ag–C bond is significantly bended (166.75°) towards the pyridyl substituent. Simultaneously, this 1D structure turns to a 2D polymeric structure via π–π stacking interaction between the imidazole and pyridyl units of two separate 1D channels. All three imidazolium salts and Ag(I)–NHC complexes 1–3 are completely characterized by using ESI-MS, IR spectroscopy and 1D/2D NMR studies. Molecular structure determination shows a significant effect of a wingtip pyridine group on the geometry of complexes 1–3.

Graphical abstract: Structural diversities in Ag(i) complexes of xylyl platform based isomeric bis-NHC ligands: effects of pyridine wingtip substituents

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Supplementary files

Article information


Submitted
18 Nov 2016
Accepted
27 Jan 2017
First published
08 Feb 2017

New J. Chem., 2017,41, 2131-2139
Article type
Paper

Structural diversities in Ag(I) complexes of xylyl platform based isomeric bis-NHC ligands: effects of pyridine wingtip substituents

B. Jana and P. Ghosh, New J. Chem., 2017, 41, 2131
DOI: 10.1039/C6NJ03609K

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