Structural Variations in Novel Silver(I) Complexes with Bitopic Pyrazole/N-Heterocyclic Carbene Ligands

The synthesis and structural characterization of several new silver complexes of L (L = a bidendate ligand of pyrazole and N-heterocyclic carbene) are described. The result shows that the choice of counterions, N-substitutions of L, and reaction conditions are crucial which lead to a variety of structural motifs, including novel metallomacrocycles [Ag2(mu-L)2]2+ with or without Ag...Ag close contact, a mononuclear [AgL2]+ complex, and a [LAg(NO3)]n coordination polymer. In particular, the nonbonding Ag...Ag distance and the overall geometry of the metallomacrocycles are controllable with different N-substitutions and counterions. All these complexes have been determined by X-ray diffraction. The solid-state aggregates are retained in solution as supported by the electrospray mass spectroscopic studies.