Syntheses and characterizations of two-dimensional heteronuclear tetracyanonickelate(II) complexes with 4-ethylpyridine and investigation of the catalytic activity of [Cd(4epy)2Ni(µ-CN)4

Abstract

Three new 2D heteronuclear tetracyanonickelate(II) complexes with 4-ethylpyridine (4epy), [Cu(4epy)2Ni(µ-CN)4]n (1), [Zn(4epy)2Ni(µ-CN)4]n (2) and [Cd(4epy)2Ni(µ-CN)4]n (3), were synthesized and characterized by vibrational (FT-IR and Raman) spectroscopy, elemental and thermal analyses, single crystal (SC-XRD) and powder X-ray diffraction (PXRD) techniques. The single crystal X-ray analysis reveals that each metal ion (Cu(II), Zn(II), and Cd(II)) is coordinated by two nitrogen atoms from 4epy ligands and four nitrogen atoms from cyanide ligands and Ni(II) ions are coordinated by four carbon atoms from cyanide ligands showing a distorted octahedral and square planar coordination geometries, respectively. The most outstanding features of the complexes are the weak intermolecular C–H⋅⋅⋅Ni interactions between the Ni(II) ion and hydrogen atom of the ethyl group of the 4epy ligand. Adjacent 2D structures are further combined by these C–H⋅⋅⋅Ni interactions, generating a 3D network. The heterogeneous catalytic activity of 3 was investigated for oxidation of some primary and secondary aliphatic or aromatic alcohols; no acid formation was observed in some aromatic alcohols after 24 h and 100% aldehyde selectivity was determined.