Synthesis and X-ray structures of Ni and Zn complexes of a novel oxa-azamacrocyclic system

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The Ni ( 5) and Zn ( 6) complexes of a novel oxa-azamacrocycle ( 4) were obtained from the reaction of 4 and the metal chlorides in equimolar amounts. The Ni complex 5 was isolated, in the solid state, as a 1:1 metal:ligand complex while 6 was obtained as a 2:1 metal:ligand complex. The X-ray diffraction structures of 5 and 6 have been obtained. The nickel atom in 5 has an octahedral geometry and it is hexa-coordinated to the four nitrogen atoms of the macrocycle, with two oxygen atoms from the water molecules in axial positions. The nickel atom is situated on the plane formed by four nitrogen atoms and also on the plane formed by four oxygen atoms. In contrast, in 6, two oxygen donors and two chlorine atoms coordinate to each zinc atom in an approximate tetrahedral arrangement such that the zinc atoms lie outside the cavity of the macrocycle.