Dicyanamido–metal(II) complexes. Part 3: Hydrolysis of the dicyanamide into amidocyanamide during its interaction with Cu(II) perchlorate and 2-pyridylcarbonyl-N,N-bis(2-pyridylmethyl)amine

Abstract

Abstract The reaction of Cu(ClO4)2, 2-pyridylcarbonyl-N,N-bis(2-pyridylmethyl)amine (DPA-CO-py) and sodium dicyanamide (Nadca) in aqueous medium led to the isolation of three complexes: {[Cu(DPA)(μ1,5-dca)]ClO4}n (1), [Cu2(pic)2(μ1,3-H2NCO–N–CN)2(H2O)2] · 2H2O (2) and Cu(pic)2 · H2O (3). The Cu2+ ion, during its complex formation with DPA-CO-py and dca not only assisted the hydrolysis of DPA-CO-py to the corresponding di(2-methylpyridyl)amine (DPA) and picolinic acid (Hpic) but also resulted in partial hydrolysis of one of the two nitrile groups of the dicyanamide, NC–N–CN− (dca) to amidocynamide, H2NCO–NH–CN. The complexes were structurally characterized and the single X-ray structures for 1 and 2 reveal their identity. Complex 1 forms a 1D polymeric chain with the dca acting as a μ1,5-bridging ligand via the terminal nitrile nitrogen atoms. A distorted SP geometry around the Cu2+ centers was achieved by the three N-atoms of the DPA and by the two nitrile groups of the bridging dca ligands. Complex 2 consists of a dimeric unit with CuN3O2 chromophore in coordination polyhedron that has a distorted SP geometry. The amidocyanamide ion, H2NCO–N–CN− acts as bis(monodentate) μ1,3-bridging ligand via the central amido and terminal nitrile nitrogen atoms whereas the picolinate anion forms a six-membered chelate ring through its pyridyl nitrogen and an oxygen atom of the carboxylate group, and the aqua water occupies the apical position of the structure. Complex 1 exhibits very weak antiferromagnetic coupling (J = −0.31 cm−1) whereas 2 shows a significant antiferromagnetic interaction between the two copper centers (J = −13.6 cm−1).