bis(2-Aryldecahydroquinolin-4-onedithiocarbamato)-metal(II) Complexes: A New Preparative Method and Characterization Along with ¹³C and ¹H NMR Decoupling Studies

Abstract

2-Aryldecahydroquinolin-4-ones, unlike mere piperidines, do not form dithiocarbamic acids on addition of carbon disulphide under alkaline condition. Invariably, xanthates are formed when carbon disulphide is added to the amine in the presence of alcohol. In the present study dithiocarbamato complexes involving 2-aryldecahydroquinolin-4-ones and Ni(II) and Cu(II) metal ions are reported for the first time. The deprotonation of 2-aryldecahydroquinolin-4-ones takes place in a NH₃/NH₄ Cl buffer medium (pH=10) in acetonitrile followed by the addition of carbon disulphide and the corresponding aqueous solution of the metal ion. The isolated complexes were of the formula M(Ldtc)₂; M(II) = Ni(II) and Cu(II), Ldtc = 2-aryldecahydroquinolin-4-onedithiocarbamate anion derivatives. These complexes were characterized by microanalyses, IR, UV, TG and mass spectral studies. A representative nickel(II) complex has also been subjected to an extensive ¹H NMR decoupling study along with ¹³C NMR and mass spectral analysis, clearly indicating the manifestation of complexation on the stereochemistry of the bicyclic ring of the ligand frame work. ¹H NMR spectral data indicated the significance of the ‘thioureide’ structure contribution to the stability of the present set of complexes which is not available from IR studies. The downfield shift of the ¹H NMR signals and the upfield shift of the C(2) carbon in ¹³C NMR spectra of the complexes indicates that the heterocyclic ring deviates from the normal chair conformation on complexation.