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Z. Naturforsch. 2014,
69b, 1188 – 1198
doi:10.5560/ZNB.2014-4175
Synthesis and Characterization of Silver(I) and Gold(I) Complexes Bearing a Pyrido-annelated N-Heterocyclic Carbene: A Rare Example of a Cocrystal Containing Two Different Gold(I) Complexes
1 Institute of Inorganic Chemistry, Johannes Kepler University Linz, Altenbergerstr. 69, 4040 Linz, Austria
2 Institute of Chemical Technology of Organic Materials, Johannes Kepler University Linz, Altenbergerstr. 69, 4040 Linz, Austria
Reprint requests to Dr. U. Monkowius. E-mail:
uwe.monkowius@jku.at
Received August 4, 2014 / published online December 19, 2014
Dedicated to Professor Hubert Schmidbaur on the occasion of his 80th birthday
The cyclohexyl-substituted imidazo[1,5-a]pyridin-2-ium hexafluorophosphate, 2a, has been prepared as precursor for the respective pyrido-annelated N-heterocyclic carbene. [(NHC)2Ag]PF6, 3, has been synthesized by the reaction of 2a with AgCl/KOH in dichloromethane (DCM). Unexpectedly, the reaction of 3 with (tht)AuBr yielded both (NHC)AuBr and [(NHC)Au(tht)]PF6 which formed a 1:1 cocrystal (4a,b). The complexes are aggregated to infinite chains, which are governed by both π-π stacking and weak aurophilic interactions. Subsequent oxidation of the co-crystalline material with CsBr3 gave (NHC)AuBr3, 5. All compounds were characterized by NMR spectroscopy, mass spectrometry and elemental
analysis. Additionally, compounds 2a and 5 were investigated by electronic spectroscopy: 2a behaves like a typical aromatic compound exhibiting absorption and fluorescence bands attributable to π-π* transitions. The Au(III) complex 5 exhibits ligand-centered fluorescence at room temperature and both ligand-centered fluorescence and a weak phosphorescence at 77 K.
Key words: Silver(I), Gold(I), N-Heterocyclic Carbenes, Crystal Structure, Cocrystal