
%0 Journal Article
%A Palaniandavar, M 
%A Natarajan, C 
%T Cobalt(II), nickel(II) and copper(II) complexes of some 2'-hydroxychalcones
%J Australian Journal of Chemistry
%D 1980/04/01
%V 33
%N 4
%P 737-745
%K 
%R https://doi.org/10.1071/CH9800737
%U https://www.publish.csiro.au/paper/CH9800737 
%X Metal(II) bis-chelates of the type ML2 [M = CoII, NiII, CuII; L = 2'- hydroxy-5'-X-chalcone where X = H, CH3, Cl] have been prepared and studied. Structures have been assessed by the measurement of magnetic moments, ligand field and infrared spectra and thermal properties. These chelates possess low-spin trans-square-planar configuration and show resistance to adduct formation in contrast to metal(II) chelates of &#946;-diketones, salicylaldehyde, o-hydroxyaryl ketones and esters and o-hydroxy-crotonophenones, which have high-spin octahedral configuration. Extensive conjugation lowers the energy of the &#960;3* orbital which enters into a very strong d&#960;-&#960;3* interaction leading to spin-pairing.     Infrared spectra indicate that the carbonyl group is perturbed only slightly by coordination to metal. A change in metal ion affects v(C=O), v(M-O) and other vibrations and the order of stability, namely, Co &#8776; Ni < Cu, inferred from these vibrations is as expected for the low-spin square configuration of the chelates. Introduction of substituents (5'-X) alters only v(M-O) significantly and the order of stability, namely, Cl > CH3 > H, derived from v(M-O) is consistent with Taft's resonance polar parameters of the substituents. All these observations are explained by the electron sink property of the phenyl group. 
