C-H⋯Pd Interactions and Cyano-Bridged Heteronuclear Polymeric Complexes

Abstract

Three new heterometallic complexes, [Cu(N-Meim)<inf>4</inf>Pd(μ-CN) <inf>2</inf>(CN)<inf>2</inf>]<inf>n</inf> (1), [Zn(N-Meim)<inf>3</inf>Pd(μ- CN)<inf>2</inf>(CN)<inf>2</inf>]<inf>n</inf> (2) and [Cd(N-Meim) <inf>2</inf>Pd(μ-CN)<inf>4</inf>]<inf>n</inf> (3), have been isolated from the reactions of M[Pd(CN)<inf>4</inf>] (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 2D network. In the Cu(II) and Zn(II) complexes, two cyanide groups of [Pd(CN) <inf>4</inf>]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⋯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⋯Pd, C-H⋯π or π⋯π interactions, forming three-dimensional network. © 2011 Elsevier Ltd. All rights reserved.