Coordination of 1-methyl-1,3-dihydro-2H-benzimidazole-2-selone to zinc and cadmium: Monotonic and non-monotonic bond length variations for [H(sebenzim(Me))](2)MCl2 complexes (M = Zn, Cd, Hg)

摘要

The reactions of 1-methyl-1,3-dihydro-2H-benzimidazole-2-selone, H(sebenzim(Me)), towards the zinc and cadmium halides, MX2 (M = Zn, Cd; X = CI, Br, I), afford the adducts, [H(sebenzim(Me))](2)MX2, which have been structurally characterized by X-ray diffraction. The halide ligands of each of these complexes participate in hydrogen bonding interactions with the imidazole N-H moieties, although the nature of the interactions depends on the halide. Specifically, the chloride and bromide derivatives, [H(sebenzim(Me))](2)ZnX2 and [H(sebenzim(Me))](2)CdX2 (X = Cl, Br), exhibit two intramolecular N-H center dot center dot center dot X interactions, whereas the iodide derivatives, [H(sebenzim(Me))](2)ZnI2 and [H(sebenzim(Me))](2)CdI2, exhibit only one intramolecular N-H center dot center dot center dot I interaction. Comparison of the M-Se and M-Cl bond lengths of the chloride series, [H(sebenzim(Me))](2)MCl2 (M = Zn, Cd, Hg), indicates that while the average M-Cl bond lengths progressively increase as the metal becomes heavier, the variation in M-Se bond length exhibits a non-monotonic trend, with the Cd-Se bond being the longest. These different trends provide an interesting subtlety concerned with use of covalent radii in predicting bond length differences. In addition to tetrahedral [H(sebenzim(Me))](2)CdCl2, [H(sebenzim(Me))](3)CdCl2 center dot[H(sebenzim(Me))](4)CdCl2, which features both five-coordinate and six-coordinate coordinate centers, has also been structurally characterized. Finally, the reaction between Cdl(2) and H(sebenzim(Me)) at elevated temperatures affords the 1-methylbenzimidazole complex, [H(sebenzim(Me))][H(benzim(Me))]Cdl(2), a transformation that is associated with cleavage of the C-Se bond. (C) 2019 Elsevier Ltd. All rights reserved.