Heterobimetallic complexes CpNiCo(CO)2(PPh3)(PhC2C6H4-R -p): their synthesis, electrochemistry and ESR

Abstract

Three new heterobimetallic acetylene complexes CpNiCo (CO)3 (PPh3) (PhC2C4H4-R-p) [R = H (2), Br (3), COCH2 (4)] have been synthesized in suitable yield (31–47%) via the reaction of (PhC2C3H4-R-p)CO2(CO)5 PPh2 with nickelcene in n-octane. The complex CpNiCo(CO)3 (Ph2C3) (1) has also been obtained in 12% by the reaction of (Ph2C2) Co2 (CO)4 with nickelcene. The complexes have been characterized by elemental analysis, IR and 1H NMR. Electrochemical study of redox couples of these complexes was presented by using cyclic voltammetry on Pt electrodes in acetone. At room temperature, all complexes underwent electrochemically reversible or guasi-reversible oneelectron oxidation or reduction to the stable radicals. The radical anions of the complexes could be easily detected by ESR method in situ electrolysis in the THF solution. The isotropic parameters, <a>CO=2.20mT, <g> = 2.052 for the radical anion of complex 1, <a>CO= 2.20 mT, <a>P = 1.42 mT, <g>=2.057 for the radical anion of complex 2, might indicate that NiCoC2 framework is a delocalized unit and the ligand obitals in the complex have more contribution to the LUMO of the complex.