Preparation of the hexadentate ligand (–)₅₄₆-2,2'-[(1,1'-Binaphthalene-2,2' diyl)bis{methylenethio(ethane-1,2-diyl)nitrilomethylidyne}]bisphenol and a study of the stereochemistry of its cobalt(III) complex

Abstract

The hexadentate ligand (-)₅₄₆-2,2'-[(1,1'-binaphthalene-2,2'- diyl)bis{methylenethio(ethane-1,2-diyl)-nitrilomethylidyne}]bisphenol (the doubly deprotonated form is abbreviated as nmep) has been prepared in the S-absolute configuration with respect to the binaphthyl group by reactions on 1,1'-binaphthyl-2,2'-dicarboxylic acid of known absolute configuration S that do not involve the asymmetric binaphthyl moiety.    

The cobalt(III) complex (+)₅₄₆-[Co(-)₅₄₆(nmep)] ClO₄ has been prepared by metal exchange of cobalt(II) ions on the zinc(II) complex followed by air oxidation. The preparative method yielded only one isomer. The complex is a uni-univalent electrolyte in nitromethane.    

Measurement of ¹³C spectra in dimethyl[D₆] sulfoxide, circular dichroism and ultraviolet/visible spectra in dimethylformamide and Dreiding molecular models indicate that the complex has the α- geometrical structure, and that the optically active binaphthyl group directs the absolute configuration at the dissymmetric cobalt centre to be Λ (IUPAC) or Δ (C₂). The thiomethyl sulfur atoms have the S-absolute configuration.