Synthesis and Characterization of an Open and a Cyclic Polyaza Complexes of Copper(II) Having Caged Moiety; Cyclization Through Copper(II) Enhanced Hydrolysis from Nitrile to Amide

The preparation, X-ray structure and properties of noncyclic (1) and cyclic (2) polyaza copper(II) complexes with caged moiety, and copper(II) enhanced hydrolysis of acetonitrile participated in the cyclization of 1 to 2 are reported. The average Cu-N distances of complex 1 and 2 are somewhat shorter than those of square-planar or square-pyramidal complexes of analogue [14]-membered ring copper(II) complexes. These results derived from the squeeze effect of caged moiety of bicyclononan. Reaction of formaldehyde and complex 1 in the presence of base in acetonitrile solution produced complex 2. In this catalytic route, coordination of acetonitrile onto Cu(II) ion, a Lewis acid, of complex 1 makes the electrophilicity of the carbon of nitrile increased. Absorption maximum of the complex 2 is shifted to somewhat shorter wavelength than that of the complex 1. It is supposed to the higher ligand field stabilization energy of complex 2, which has cyclized ligand, comparing that of the complex 1, which has open ligand. These complexes are stable against disproportionation in copper(I) state.