Syntheses, crystal structure and electrochemical characterization of ferrocene-containing nickel(II) complexes with 4,11-dihydro-5,7,12,14-tetramethyldibenzo[b,i][1,4,8,11]tetraazacyclotetradecine

In the title complexes, {[(η-C5H5)Fe(η-C5H4)(CO)](C22H21N4)Ni} (1) and {[(η-C5H5)Fe(η-C5H4)(CO)]2(C22H20N4)Ni} (2), one and two electroactive ferrocenes (Fc) were grafted onto the methine of the nickel complex Nitmtaa (H2tmtaa = 4,11-dihydro-5,7,12,14-tetramethyldibenzo[b,i][1,4,8,11]tetraazacyclotetradecine) through the carbonyl groups. The two new complexes were characterized by IR, UV, MS and NMR spectra as well as by DSC measurements. The crystal structure of 1 was determined. Ni coordinates to four nitrogen atoms of tmtaa, and it is almost in the same plane as the N4 plane. The mean Ni–N bond distance in the N4 plane is 1.866 Å. The non-planar, saddle-shaped conformation of H2tmtaa is almost retained in the nickel complex. The symmetry axis of ferrocene is almost parallel to the N4 plane in Nitmtaa. The dihedral angle between the N4 plane in Nitmtaa and the cyclopentadienyl ring in ferrocene is 98.5°. The electrochemistry of 1 and 2 was studied by cyclic voltammetry in CH2Cl2/1 × 10−1 M n-Bu4NClO4 using a glass carbon working electrode. Because of the electron transfer between the electroactive ferrocene and the completely conjugated system of Nitmtaa, the complexes show novel electrochemical properties and the ferrocenes in 1 and 2 act as electron acceptors.

Two novel ferrocene-containing tmtaa (H2tmtaa = 4,11-dihydro-5,7,12,14-tetra- methyldibenzo[b,i][1,4,8,11]tetraazacyclotetradecine) complexes {[(η-C5H5)Fe(η-C5H4)(CO)](C22H21N4)Ni} (1) and {[(η-C5H5)Fe(η-C5H4)(CO)]2(C22H20N4)Ni} (2) have been synthesized and characterized. The crystal structure of 1 shows that the symmetry axis of ferrocene is almost parallel to Nitmtaa. In 1 and 2, the ferrocene groups act as electron acceptors, not electron donors.Figure optionsDownload as PowerPoint slide