Incorporation of lead(II) by copper(II)-salicylaldimine type ligand complexes: Cation-π interactions in controlling the distortion of coordination geometry around lead(II)

Two tri-nuclear, hetero-metallic copper(II)-lead(II) complexes, [(CuL1)(2)Pb(NCS)(2)] (1) and [(CuL2)(2)Pb(NCS)2(]) (2) have been synthesized by reacting the "ligand-complex" [CuL1] and [CuL2] respectively with Pb(CH3COO)(2)center dot 3H(2)O and ammonium thiocyanate (where H2L1 = N,N'-bis(salicylidene)-1,3-propanediamine and H2L2 = N,N'-bis(alpha-methylsalicylidene)-1,3-propanediamine are the tetradentate di-Schiff base ligands) in EtOH-water medium. Both complexes have been characterized by X-ray single crystal structural analyses. In both structures, the central Pb(II) is six-coordinate, being bonded to four oxygen atoms from two terminal square planar CuL units and a couple of thiocyanate nitrogen atoms. The geometry around Pb(B) in both complexes is far from ideal octahedron and the distortion is more severe in (2). The coordination environment around all Cu(II) centres are square planar with different degrees of tetrahedral distortions. There are significant intra- and intermolecular cation-it interactions between the phenyl rings of the Schiff base and Cu(II) that seem to control the distortion around Pb(II).