C-H center dot center dot center dot Pd interactions and cyano-bridged heteronuclear polymeric complexes

Abstract

Three new heterometallic complexes, [Cu(N-Meim)(4)Pd(mu-CN)(2)(CN)(2)](n) (1), [Zn(N-Meim)(3)Pd(mu-CN)(2)(CN)(2)](n) (2) and [Cd(N-Meim)(2)Pd(mu-CN)(4)](n) (3), have been isolated from the reactions of M[Pd(CN)(4)] (M = Cu(II), Zn(II) or Cd(II)) and N-Meim (N-methylimidazole) with in different molar ratios. All complexes have been characterized by X-ray analyses, vibrational (FT-IR and Raman) spectra, thermal and elemental analyses. The crystallographic analysis reveals that the crystal structures of 1 and 2 are 1D coordination polymer, while 3 presents a 20 network. In the Cu(II) and Zn(II) complexes, two cyanide groups of [Pd(CN)(4)](2-) coordinated to the adjacent M(II) ions and distorted octahedral and square pyramidal geometries of complexes are completed by four and three nitrogen atoms of N-Meim ligands, respectively. The Cd(II) ion is six-coordinate, completed with the two nitrogen atoms of N-Meim ligands in the axial positions and the four nitrogen atoms from bridging cyano groups in the equatorial plane. The most striking features of complexes 1-3 are the presence of obvious C-H center dot center dot center dot Pd hydrogen-bonding interactions between the Pd(II) and hydrogen atoms of N-Meim ligand. This weak hydrogen bonding plays a crucial role in the architecture of the network polymers. The adjacent chains are held together by C-H center dot center dot center dot Pd, C-H center dot center dot center dot pi or pi center dot center dot center dot pi interactions, forming three-dimensional network. (C) 2011 Elsevier Ltd. All rights reserved.