C−H⋯Pd interactions and cyano-bridged heteronuclear polymeric complexes

Abstract

Three new heterometallic complexes, [Cu( N- Meim) 4Pd(μ-CN) 2(CN) 2] n ( 1), [Zn( N- Meim) 3Pd(μ-CN) 2(CN) 2] n ( 2) and [Cd( N- Meim) 2Pd(μ-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 2D 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⋯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.