Complexes of the ethylpyridines with the halides of cobalt(II), nickel(II) and copper(II)

Abstract

A series of complexes has been prepared with the halides of cobalt(II), nickel(II), copper(II) and 2-,3-,4-ethylpyridine. The compounds were essentially all octahedral with the exception of those formed between 2-ethylpyridine and the cobalt(II) halides. The stereochemical configurations were deduced using spectral and magnetic properties. The decomposition of the complexes was studied by thermogravimetry and differential thermal analysis.This work is a continuation and an extension of previously reported studies [1-9] on the coordination compounds formed between the halides of cobalt(II), nickel(I1) copper(II) and 2-,3-,4-ethylpyridine. The variation of the ethyl constituent in the 2-, 3-and 4-position of the pyridine ring means that both the donor tendency of the N ring atom and the steric influence of the substituted pyridine molecule can be further investigated. The thermal decomposition of the compounds has been studied. Information regarding the stereochemistry of the compounds was obtained using electronic absorption spectra, far infrared spectra and magnetic measurements over the temperature range 300-100 K. ExperimentalThe complexes were prepared by dissolving the appropriate metal halide in hot ethanolic solution and adding an excess of the nitrogen-base dissolved in ethanol. The precipitated complexes were washed with ethanol and air-dried. The complexes prepared by this method are given in Table 1. References are given to previous preparations; where no reference is given it is believed that these are new compounds.Thermal decomposition studies were carried Out in air on a Stanton Redcroft Model TR-O1 Thermobalance with a DTA attachment.Electronic spectra were obtained on a Beckman ACTA M-IV spectrophotometer using 1 cm cells. The solvent used was AR Chloroform dried over molecular sieves. Far infrared spectra were obtained on a Beckman IR 720 M interferometer using a polythene matrix to support the complexes.

The preparation, characterization and thermal analysis studies on complexes of cobalt(II) with 2-, 3-, 4-cyanopyridines

“…The complexes would appear to fall into three groups: the hydrated complexes which first dehydrate below 373 K and then decompose at temperatures between 702 K and 773 K directly to Co304; the anhydrous complexes which similarly decompose between 340 K and 670 K to Co30 4 and the anhydrous complexes which give intermediate decomposition products between 420 K and 530 K and eventually decompose to give cobalt(ll)chloride and cobalt(ll)bromide. Comparison of these complexes to those reported previously for pyridine methylpyridines, ethylpyridines and cobalt(ll) [10,11] show that the trend in decomposition is similar.…”

“…The complexes have values of 10 Dq <4400 cm-1 [13]. The presence of the 4A2(F) ground state term is shown by the fact that the magnetic moments for the complexes do not vary over the temperature range 300-100 K. The compounds have magnetic moments between 4.23-4.45X 10 -23 Am2 which agree with a tetrahedral environment for the cobalt(l I) ion [10] and obey the Curie-Weiss law with positive values of 0. The visible spectrum of tris(2-cyanopyridine)cobalt(ll)iodide would suggest a trigonal bipyramidal structure [14].…”

The preparation, characterisation and thermal analysis studies on complexes of cobalt(II), nickel(II), and copper(II) with 3-picolylamine

“…The bromo complex undergoes an endothermic reaction at 418 K followed by an exothermic reaction at 646 K with loss of the 3-picolylamine and bromine and the formation of Co304. The electronic spectra of the complexes are typical of the cobalt(II) ion in an octahedral environment [1] and have Dq > 440 cm-1 [4]. The magnetic data for the compounds (Table 3) The nickel complexes have stoichiometry Ni(CNS)2(3-pa)2, NiCl2(3-pa)4 and NiBr2(3-pa)2.…”