Synthesis and characterisation of n-acylsubstituted amid and thioamide complexes of some divalent transition metal sulphates

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Acyclic N-acylsubtituted amides, RCONHCOŔ (I, R=Ŕ=Ph, II, R= Ph, Ŕ=Me) and thioamides, RCSNHCOR (III, R=Ŕ=Ph; IV, R=Me, Ŕ=Ph) were prepared. The N-Benzoylthiobenzamide (III) was synthesized as a new compound and characterized. These ligands were then employed in synthesizing complexes with some first row divalent transition metal sulphates (M(II) =Mn (II), Fe(II), Co (II) Ni(II), Cu(II) and Zn (II)) for the first time using solid-solid interaction. The decomposition temperatures, the temperature dependence of the solubilities and heat of solution in some organic solvents, of these imides and thioimides reported, give an indication of a stronger hydrogenbonding association in RCONHCOR (NH…O=C) than in RCSNHCOR (N-H…S=C). The infra – red spectra of these imide and thiomide complexes reveal that RCONHCOR co-ordinates to M(II) through the oxygen atoms of the imide group (-CO-NH-CS) in trans-trans configuration whilst M(II) complex of RCSNHCOR involve co-ordination through the oxygen and sulphur atoms, of the thio-imide group (-CO-NH-CS-) also in the trans-trans disposition. The replacement of the methyl group in N-Benzoylacetamide with a phenyl group shifts the Imide Ia and Ib bands to lower frequencies, whereas a shift to higher frequencies is observed for the corresponding Imide Ia and Ib bands in going from N-Acetythiobenzamide to N-Benzoylthiobenzamide. Consequently the Metal-ligand bands in N-Acetylthiobenzamide are stronger than the corresponding bands in N-Benzoylthiobenzamide. A similar trend is observed in the case of N-Benzoylacetamide series on one hand, and N-Benzoylbenzamide on the other. The electronic spectral data, supported by magnetic susceptibility data, suggested an octahedral environment for Mn (II), Fe (II), Co (II), Ni (II) and Zn (II) complexes whilst the Cu (II) complexes exhibit square planar configuration.
A thesis submitted to the Board of Postgraduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirements for the award of the Degree of Master of Philosophy, 1988