CRYSTAL-STRUCTURES OF [AGHGL2(NO3)]N, WHERE LH = 2-OXAZOLIDONE AND BETA-PROPIOLACTAM - FORMATION OF HELICAL CHAINS AND NEW 12-MEMBERED AG/HG METALLAMACROCYCLIC RINGS IN THE PROPIOLACTAM COMPLEX

Reaction of 2-oxazolidone (C3H5NO2) or beta-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 interactions bridge these tetrameric units so as to produce loosely linked polymeric sheets. In compound 2 the silver atoms are linked by twisted Hg(beta-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.