Metal complexes with pendant-armed oxaazamacrocycles. The crystal structures of dimeric Ca(II) and Sr(II) complexes

A new series of alkaline-earth and transition metal complexes of Ca(II), Sr(II), Ba(II), Co(II), Ni(II) and Cu(II) with two pendant-arm oxaaza macrocyclic ligands, L1 and L2, with N4O2 and N4O3 donor sets, respectively, were synthesized by reaction of the ligand and the appropriate perchlorate salt in refluxing acetonitrile. The reactions gave analytically pure products that were characterized by elemental analysis, FAB mass spectrometry, IR and 1H NMR spectroscopy. The crystal structure of L1·3H2O, [Sr2(L2-H)2(ClO4)2] and [Ca2(L2-H)2(ClO4)2]·2.5CH3CN could be also determined. ystal structures of the Ca(II) and Sr(II) complexes with L2 show similar dimeric compounds with the two metal ions joined through the deprotonated phenolic oxygen from two salicylaldehyde groups. Both metal ions are in a seven coordination environment. In these dimeric compounds each metal ion is exomacrocyclicly bonded to the four nitrogen atoms from one ligand molecule, one oxygen atom from a monodentate perchlorate anion and the bridge oxygen atom of the salicylaldehyde group from both ligand molecules.