(2,2',2''-Terpyridine)palladium(II) complexes of phenylcyanamide and 1,4-dicyanamide-2,5-dimethylbenzene ligands

摘要

A series of square planar terpyridinepalladium(II) complexes of phenylcyanamide anion ligands (i.e. ((trpy)Pd(pcyd)) (PF$sb6))$ have been synthesized and characterized by IR, $sp1$H NMR, UV-vis spectroscopies and X-ray crystallography. The crystal structure of ((trpy)Pd(pcyd)) (PF$sb6)$ shows that the complex molecule is almost planar and the Pd-NCN bond is bent having a bond angle of 146.4$spcirc.$ The planarity of the complex is important since it allows for the formation of $pi$ stacks in the crystal lattice. The formation of $pi$-stacks in organic charge transfer (CT) salts has been shown to result in highly conductive materials. A mononuclear terpyridinepalladium(II) complex of 1,4-dicyanamide-2,5-dimethylbenzene radical anion ligand and a dinuclear terpyridinepalladium(II) complex of 1,4-dicyanamide-2,5-dimethylbenzene dianion ligand have also been prepared and characterized by IR, $sp1$H NMR, UV-vis spectroscopies and cyclic voltammetry. Almost all of the above complexes show an unusual ligand to metal charge-transfer (LMCT) absorption in the range 360-700 nm. It is suggested that the bending of cyanamide group makes the mixing of metal's $sigmasp*$ and ligand's $pisb{rm nb}$ orbitals possible and results in the LMCT absorption.