Role of the group 12 metals in tuning the structural motif: From complexes to halometallate salts of 3-carbamoyl-1-methylpyridinium

Abstract

Reactions of the group 12 metal bromides and iodides with 3-carbamoyl-1-methylpyridinium iodide (LI), the quaternary salt of the nicotinamide, were investigated. The [ZnBr2(L–H)2] (1), [ZnI2(L–H)2] (2), [L]2[CdBr4] (3), [L]2[CdI4] (4), {[L][HgBr3]}n (5) and {[L][HgI3]}n (6) have been prepared and characterized by vibrational spectroscopy (IR, Raman) and thermal methods (TG/DSC), and single crystal structures of 1, 2, 4 and 6 were determined by X-ray structure analysis. The reactions of zinc(II) halides performed under solvothermal conditions afforded complex compounds (1 and 2), where coordination of 3-carbamoyl-1-methylpyridinium was possible only upon deprotonation of the amide nitrogen. In both complexes, zinc(II) exhibits tetrahedral coordination geometry with two halide ions and two amide nitrogens in the coordination sphere. For cadmium(II) and mercury(II) halides, reactions performed at ambient as well as solvothermal conditions led to the preparations of tetra- (4) or trihalometallate salts (6) of 3-carbamoyl-1-methylpyridinium, respectively. In cadmium compound (4) monomeric, [CdI4]2−, while in mercury(II) compound (6) polymeric, [HgI3]n−, structures are found. Furthermore, in 4 and 6, the self-complementary amide hydrogen bonds appear to be the main driving force for establishing their crystal structures; in 1 and 2, after deprotonation of the amide nitrogen, the formation of the amide hydrogen bonds does not occur.