Sulphur-nitrogen chelating agents. II. Metal complexes of 2-(2-Methylthioethyl) pyridine

Abstract

2-(2-Methylthioethyl)pyridine (N-SMe) has been prepared and its structure has been confirmed by N.M.R. measurements. Complexes with palladium(II), platinum(II), copper(II), copper(I), silver(I), and mercury(II) were obtained but attempts to prepare complexes of cobalt(II) and nickel(II) were unsuccessful. The mono-chelated complexes MX₂(N-SMe) (M = Pd, Pt; X = Cl, Br, I, SCN), CuX₂(N-SMe) (X = Cl, Br), AgClO₄(N-SMe), and HgCl₂(N-SMe), and the bis-chelated complexes [M(N-SMe)₂](ClO₄)₂ (M = Pd, Pt, Cu, Hg) and [Cu(N-SNe)₂]ClO₄ were characterized. Conductimetric titrations of [Pd(N-SMe)₂](ClO₄)₂ in nitrobenzene gave end-points after the addition of two equivalents of halide ion due to the loss of one molecule of ligand to yield PdX₂(N-SMe). The platinum complex [Pt(N-SMe)₂](ClO₄)₂ gives two end-points, the first corresponding to the formation of [Pt(N-SMe)₂X]+ (X = Br, I). The solid reflectance spectra of CuX₂(N-SMe) differ from the absorption spectra in nitromethane solution, indicating a polymeric tetragonal structure in the solid state. The ligand molecules in [Cu(N- SMe)₂](ClO₄)₂ are readily replaced by pyridine. This complex can be reduced to the copper(I) complex [Cu(N-SNe)₂]ClO₄. The infrared spectrum of AgClO₄(N-SMe) seems to indicate that the perchlorato groups are coordinated and the insolubility of the compound suggests a polymeric structure. The mercury complexes apparently contain tetrahedral mercury(II).