Transition Metal Complexes Induced Amidine Synthesis, Structure And Characterization

The nucleophilic addition of amines to nitriles provides a convenient route to obtain amidines, which are important molecules in organic synthesis, inorganic synthesis and medicinal chemistry. We have investigated the reactions of the heteroaryl amines with nitrile in the presence of transitional metal compounds includes the perchlorate of Cu, Co, Ni. Herein we reported our research results about the transitional metal-promoted addition of 2-amino-1,3,4-thiadiazole to acetonitrile, leading to nine novel amidine complexes. 1. Cu(HL)2 2. [Cu(H2L)2](ClO4)2 3. [Cu(H2L)2](ClO4)2 4. [Cu (H2O)(H2L)2](ClO4)2·H2O 5. [Cu2(H2L)4(4,4'-bpy)](ClO4)4·(4,4'-bpy)2·(CH3CN)4 6. [Co (H2L)(HL)](ClO4)2 7. [Co(HL)2(Py)2](ClO4)·CH3CN 8. [Ni(H2L)(HL)](ClO4)2 9. Ni(HL)2Complex 1, 9 and 6, 8 have almost the same cell parameter, although they are the different metal compounds. What` more, complex 2 and 3 have the same molecular, formular but different coordinated environment, while the molecules of the two compounds arrange in the different direction, and the distance between ClO4- and metal ion are distinct.It is interesting to note that one or two protons of amidine ligands in some complexes are lost while the other amidine ligands are not deprotonated. There is a square planar unit MN4(M=Cu,Co, Ni) in all of the complexes, the imino-nitrogen atoms from the amidine ligand and heterocycle coordinated to the central metal ion, affording to two stable six-membered ring.Complex 1～9 were charactered by X-Ray diffraction, IR spectroscopy, and UV spectroscopy, cyclic voltammetry. The reaction mechanism for the formation of amidine and amidinated complexes was discussed.