Crystal structure of hetero(bi- and tetra-)metallic complexes of compartmental Schiff bases uniting uranyl and transition metal (Ni2+, Cu2+) ions

The first crystal structures of hetero(bi- and tetra-)metallic uranyl/3d metal ion complexes with hexadentate Schiff bases are reported. The two Schiff bases N,N'-bis(3-hydroxysalicylidene)-1,3-propanediamine (H4L-1) and N,N'-bis(3-hydroxysalicylidene)-2-methyl-1,2-propanediamine (H4L2) have been used. Both ligands complex the 3d metal ion (Ni2+ or Cu2+) in the inner N2O2 coordination site, with n additional axial pyridine ligands (0 less than or equal to n less than or equal to 2) and the uranyl ion in the outer O-4 cavity. In order to match the usual pentagonal bipyramidal geometry, the coordination sphere of the uranyl ion is completed by either a chlorine atom, giving the binuclear complex [Ni(py)(2)(L-1)UO2Cl][Hpy], or by a water molecule, resulting in the hydrogen bonded binuclear dimer [Ni(L-2)UO2(H2O)](2) or by a phenoxide oxygen atom of a second Schiff base in the tetranuclear [Cu(py)(L-1)UO2](2) species. (C) 2003 Elsevier Ltd. All rights reserved.