Synthesis and spectroscopic characterisation of cobalt(II), nickel(II) and copper(II) complexes with 5-methyl-1-(2′-pyridyl)pyrazole-3-carbohydrazide

The chelating behaviour of the title pro-ligand, 1 (MPyPzCH), is demonstrated by preparation of a range of its distorted-octahedral Co-II, N i(II) and Cu-II complexes with various counter ions, X (X = Cl, Br, NO3, SCN, BF4, or CIO4)The neutral, tetradentate ligand appears to bind through the pyrazolyl 2(N) and pyridyl 1'(N,) amidic oxygen (ketonic form) and the terminal N of the hydrazide residue, respectively. The anions W in all cases are coordinated. The ESR spectra of some of the Cu-ll complexes indicate dx(2)-y(2) as ground state.