Complexes of cobalt(II) and nickel(II) with some bidentate thiosemicarbazones

Abstract

Some new, and some previously reported, bis-chelate complexes of bidentate thiosemicarbazones with a range of cobalt(II) and nickel(II) salts have been isolated, and they have been characterized by infrared and electronic spectra, and by magnetic measurements. The complexes are those of the thiosemicarbazones of acetone, diethyl ketone and cyclopentanone with nickel(II), and the thiosemicarbazones of acetone, ethyl methyl ketone, cyclopentanone and benzaldehyde with cobalt(II). They all have the composition M(tsc)₂X₂ (some being obtained with solvent of crystallization), and the influence of metal ion M, the thiosemicarbazone ligand tsc, and the anion X on the structures is examined. The non-aromatic thiosemicarbazones gave five-coordinate halo complexes of general type [M(tsc)₂X] X (M = Co, Ni; X = halide). The nitrates appear to have formally six-coordinate structures of type [M(tsc)₂(NO₃)]NO₃ involving one bidentate nitrate, although the electronic spectra suggest that the coordination environments of the metal ions resemble those of five- rather than six-coordinate complexes. The thiocyanato and perchlorato complexes are considered to be five-coordinate with cobalt and six-coordinate with nickel. Benzaldehyde thiosemicarbazone (bztsc) did not yield nickel(II) complexes, but gave tetrahedral complexes [Co(bztsc)₂] X₂ with X = halide, and a six-coordinate thiocyanato complex [Co(bztsc)₂(NCS)₂] whose reflectance spectrum may show the effects of tetragonal distortion.