Reactions of pyridyl donors with halogens and interhalogens: an X-ray diffraction and FT-Raman investigation

Three different N-donors L, namely N-ethyl-N′-3-pyridyl-imidazolidine-4,5-dione-2-thione (1), N,N′-bis(3-pyridylmethyl)-imidazolidine-4,5-dione-2-thione (2), and tetra-2-pyridyl-pyrazine (3), bearing one, two and four pyridyl substituents, respectively, have been reacted with halogens X2 (X = Br, I) or interhalogens XY (X = I; Y = Cl, Br). CT σ–adducts L · nXY, bearing linear N⋯XY moieties (L = 3; X = I; Y = Br, I; n = 2), and salts containing the protonated cationic donors HnLn+ (L = 1 − 3; n = 1, 2, 4), counterbalanced by Cl−, Br−, I3-, Br3-, I5-, Br5-, I2Br−, I3Br4-, or ICl2- anions, have been isolated. Among the reactions products, (H1+)Cl−, (H1+)Br−, (H2+)I3-, (H232+)(ICl2-)2, and 3 · 2IBr have been characterised by single-crystal X-ray diffraction. The nature of the products has been elucidated based on elemental analysis and FT-Raman spectroscopy supported by MP2 and DFT calculations.

Graphical abstractX-ray diffraction, FT-Raman spectroscopy and MP2/DFT theoretical calculations have been used to elucidate the nature of the products isolated from the reactions between three pyridyl donors, N-ethyl-N′-3-pyridyl-imidazolidine-4,5-dione-2-thione (1), N,N′-bis(3-pyridylmethyl)-imidazolidine-4,5-dione-2-thione (2), and tetra-2-pyridyl-pyrazine (3), and Br2, I2, IBr, and ICl. Both σ-type CT-adducts and polyhalide salts of the protonated donors have been characterised.Figure optionsDownload full-size imageDownload as PowerPoint slide