Preparation and structure of silver complexes with 4-nitroimidazole

Abstract

The reaction of 4-nitroimidazole (NO 2 ImH) with AgNO 3 and AgBF 4 in neutral or weakly acidic aqueous media yielded the insoluble [Ag(NO 2 Im)] compound, whose infrared and 13 C NMR spectra are consistent with a polymeric chain of deprotonated ligands bridging silver atoms via the endocyclic nitrogen atoms. In strongly acidic solution, [Ag(NO 2 ImH) 2 ]X salts (X = NO 3 , BF 4 ) were obtained and their crystal structures were determined. [Ag(NO 2 ImH) 2 ]NO 3 : monoclinic, P2/n, a = 14.214(1), b = 12.571(2), c = 14.222(1) Å, β = 111.38(7)°, Z = 8, R = 0.021, 3443 observed reflections; [Ag(NO 2 ImH) 2 ]BF 4 ; monoclinic, P2 1 /c, a = 9.543(4), b = 6.478(2), c = 20.869(9) Å, β = 90.84(3)°, Z = 4, R = 0.027, 1646 observed reflections. In both compounds, the two-coordinated metal forms roughly collinear bonds to two neutral ligands via the endocyclic nitrogen atom adjacent to the nitro group. One oxygen of each nitro group makes a secondary Ag—O bond near the equatorial plane. The anions are hydrogen bonded to the ligand N—H groups and do not directly interact with the metal. Solution 1 H and 13 C NMR spectra show that the cationic complexes dissociate in DMSO. The infrared and CP-MAS 13 C NMR spectra are discussed in connection with the coordination patterns observed. Keywords: silver, imidazole, crystal structure, infrared spectroscopy, nuclear magnetic resonance.