Copper(II) Prevents the Saccarine-Dialkylcyanamide Coupling by Forming Mononuclear (Saccharinate)(Dialkylcyanamide)copper(II) Complexes

Abstract

The reaction in the system CuII/sacNa(H)/NCNR2 (sacNa(H) = sodium saccharinate (saccharin); R = Me, Et) results in the formation of the complexes [Cu(sac)2(NCNR2)(H2O)2] (R = Me 1, Et 2) instead of the expected products derived from the saccharin–cyanamide coupling. Complexes 1, 2, and hydrate 1·2H2O were characterized by IR, AAS (Cu%), TGA, and also by single-crystal X-ray diffraction for 1 and 1·2H2O. An integrated computational study of model structure 1 in the gas phase demonstrates that the Cu–Ncyanamide and Cu–Nsac coordination bonds exhibited a single bond character, polarized toward the N atom and almost purely electrostatic, with the calculated vertical total energies for the Cu–Ncyanamide and Cu–Nsac of 43.6 and 156.4 kcal/mol, respectively. These data confirmed that the copper(II) completely blocks the nucleophilic centers of ligands via coordination, thus preventing the saccharin–cyanamide coupling.