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Coinage Metal Complexes of the Carbenic Tautomer of a Conjugated Mesomeric Betaine Akin to Nitron

Authors :
Siemeling, Charlotte Thie
Clemens Bruhn
Michael Leibold
Ulrich
Source :
Molecules; Volume 22; Issue 7; Pages: 1133
Publication Year :
2017
Publisher :
Multidisciplinary Digital Publishing Institute, 2017.

Abstract

This study was motivated by our recent observation that the analytical reagent Nitron (2) is an “instant carbene”, whose reaction with coinage metal salts MX afforded complexes of its carbenic tautomer 1,4-diphenyl-3-phenylamino-1,2,4-triazol-5-ylidene (2′). Our aim was to establish an alkyl homologue of 2 in order to achieve a carbenic tautomer of higher donicity. For this purpose 1-tert-butyl-4-methyl-1,2,4-triazol-4-ium-3-tert-butylaminide (6) was synthesized. Its reactions with MX afforded complexes of the carbenic tautomer 1-tert-butyl-3-tert-butylamino-4-methyl-1,2,4-triazol-5-ylidene (6′). With a stoichiometric ratio of 1:1 complexes of the type [MX(6′)] were obtained. A ratio of 2:1 furnished complexes of the type [MX(6′)2] or [M(6′)2]X. 6′ is a better σ-donor and less electrophilic than 2′ according to NMR spectroscopic data of 6H[BF4] and 6′ = Se, respectively, and IR spectroscopic data of [RhCl(6′)(CO)2] confirm that its net electron donor capacity is superior to that of 2′. A comparison of the complexes of 2′ and 6′ reveals two pronounced structural differences. [CuX(6′)2] (X = Cl, Br) exhibit more acute C‒Cu‒C bond angles than [CuX(2′)2]. In contrast to [CuCl(2′)], [CuCl(6′)] aggregates through Cu···Cu contacts of ca. 2.87 Å, compatible with cuprophilic interactions. These differences may be explained by the complementary steric requirements of the t-Bu and the Me substituent of 6′.

Details

Language :
English
ISSN :
14203049
Database :
OpenAIRE
Journal :
Molecules; Volume 22; Issue 7; Pages: 1133
Accession number :
edsair.multidiscipl..3a77bbba66cbe1cbf1ef024cc6425fac
Full Text :
https://doi.org/10.3390/molecules22071133