Complexes of copper and silver with tetracyanobiimidazole

We have recently reported the synthesis and properties of a remarkable new ligand 4,4′,5,5′-tetracyano-2,2′-biimidazole (H₂Tcbiim).¹ This acidic ligand readily binds metal ions in its dianionic form and appears to act as a strong pi acceptor. Its use as a quadridentáte bridging ligand allows study of metal-metal interactions through a planar conjugated system and extends earlier work by us² and by Hendrickson and coworkers³ on 2,2′-biimidazole. In this communication we report on the reactions of H₂Tcbiim with Ag(I), Cu(I) and Cu(II) salts.