Molecular Switching through Chalcogen-Bond-Induced Isomerization of Binuclear (Diaminocarbene)PdII Complexes

Abstract

Binuclear diaminocarbene complexes, which form as a regioisomer mixture in the reaction between isocyanide–palladium(II) complex cis-[PdCl2(CNXyl)2] and 1,3-thiazol-2-amine, are able to exchange an anionic chloride ligand with other halides, such as Br or I. This process also affords binuclear complexes as mixtures of kinetically and thermodynamically controlled regioisomers. In CDCl3 solutions, we observed interconversion of kinetically and thermodynamically controlled regioisomers. The results of the DFT calculations revealed that in CHCl3 solution, each pair of the isomers exhibited two different types of chalcogen bonding such as S···X or S···N; the presence of CBs for two complexes in the solid state was also proven through X-ray crystallographic study. Based on the combined experimental and theoretical data, it could be concluded that thermodynamic favorability for the formation of thermodynamically controlled regioisomers increases in the Cl < Br ≈ I row and correlate well with the energy difference between S···N and S···X (X = Cl, Br, I) chalcogen bonds in kinetically and thermodynamically controlled products. This means that it is possible to change the structure of metallocycles in binuclear diaminocarbene complexes by simply replacing one halide ligand with another.