Well-Defined [Silver(I)(Pyridine-Containing Ligand)] Complexes

Nitrogen containing macrocyclic molecules are naturally occurring species that play a vital role in biological system, such as porphrins, corrins and chlorins. In past years, our attention turned to the development of synthetic pathways that allow to obtain a new class of tetraaza macrocyclic ligands containing pyridine in few synthetic steps, in good yield, and starting from economic and commercially available starting materials The copper(I) complexes of these Pc-L* ligands have been successfully employed as catalyst in the Henry reaction and in the enantioselective cyclopropanation of alkenes. More recently, the silver(I) complexes have demonstrated to be active catalysts for some domino4 and multicomponent reactions.5 Here we report on new chiral [Ag(I))(Pc-L*)] complexes that were synthesized and fully characterized, including structures of some species determined by X-ray diffraction on single crystals. They show a rich coordination chemistry, demonstrating both the sigma-philic (alcohol and nitrile coordination) and the pi-philic (alkyne coordination) nature of silver. The eta2 coordination mode of the naphthyl pendant arm of the ligands on silver has been observed in solution by NMR experiments. 2D-NMR spectroscopy revealed the presence of positive cross peaks due to rotational processes and the rate of rotation was measured by using 2D Exchange Spectroscopy (EXSY).