Crystal structures of [AgHgL2(NO3)]n, where LH = 2-oxazolidone and β-propiolactam: Formation of helical chains and new 12-membered Ag/Hg metallamacrocyclic rings in the propiolactam complex

Abstract

Reaction of 2-oxazolidone (C3H5NO2) or β-propiolactam (C3H5NO) with mercury(II) acetate and silver(I) nitrate in methanol leads to the formation of the polymeric heterometallic complexes [AgHg(C3H4NO2)2(NO3)]n (1) and [AgHg(C3H4NO)2(NO3)]n (2), respectively; the structures of which have been determined by X-ray diffraction methods. In each case, the deprotonated organic ligands bind to the mercury via nitrogen with nearly linear NHgN bonding and to the silver atom via oxygen. Despite the similar nature of the ligands, totally different three-dimensional assemblies are produced. Complex 1 is dimeric with a folded Ag2O2 ring in which the bridging oxygen atoms are provided by the exocyclic oxygen atoms of the 2-oxazolidone anions. These dimers are further linked in pairs to produce a “stepped” Ag4O4 species. Each silver atom is six-coordinate. Weak electrostatic, anion-mediated interact ions bridge these tetrameric units so as to produce loosely linked polymeric sheets. In compound 2 the silver atoms are linked by twisted Hg(β-propiolactam)2 bridges to form a helical chain. Each turn of the helix is bridged by a nitrate anion linking between adjacent silver atoms forming a 12-membered metallamacrocycle. Here the silver atoms are tetrahedrally coordinated.