Axel Schulz and colleagues, Universität Rostock, Germany, synthesized salts bearing the tetracyanopyrrolide anion (TCP) in good yields starting from tetracyano-1,4-dithiin (3) and sodium azide.
The structure and bonding of such salts is discussed for the first time. The anion can be referred to as a pseudohalide with π bonds highly delocalized over the entire anion including the four cyano groups. The planar TCP anion is C2v symmetric. It represents a multifunctional binary CN ligand as demonstrated in a series of state structures.