Insights into the Topology and the Formation of a Genuine ppσ Bond: Experimental and Computed Electron Densities in Monoanionic Trichlorine [Cl3]−

Abstract

So far, several publications have discussed the bonding concepts in polyhalides on a theoretical basis. In particular, the trichlorine monoanion is of great interest because its structure should be symmetrical and show two equidistant Cl−Cl bonds. However, apart from matrix-isolation studies, only asymmetric trichlorine anions have been reported so far. Herein, the trichlorine monoanions in 2-chloroethyltrimethylammonium trichloride [NMe3EtCl][Cl3], 1, tetramethylammonium trichloride [NMe4][Cl3], 2, and tetrapropylammonium trichloride [NnPr4][Cl3], 3, are analysed. High-resolution X-ray structures and experimental charge density analyses supported by periodic quantum-chemical calculations provide insight into the influence of the crystalline environment on the structure of these [Cl3]− anions as well as into the progress of the bond formation between a dichlorine molecule and a Cl− anion.