Tetrameric silver(I) complex with bridging N-heterocyclic carbene ligands: [(iPr Im)Ag(NO3)]4

The complex [(iPrIm)Ag(NO3)]4 (iPrIm = N,N′-bis(isopropyl)imidazol-2-ylidene) was obtained by reacting Ag(cod)NO3 with [(iPrIm)AgCl]2 in CH2Cl2. The solid-state structure reveals that the complex is composed of a tetrameric core with two different ligands coordinated in both terminal and bridging mode, giving rise to a final formulation better described as [Ag4(iPrIm)2(μ-iPrIm)2(ONO2)2(μ,κO-ONO2)2]. DFT calculations found that the tetramer can exist in two almost isoenergetic isomers, one corresponding to the crystallographic structure and one with terminal-only carbene ligands. Conversely, with halide, only one isomer can be formed.