Reaction chemistry of 1,1′-ferrocene dicarboxylate towards M(II) salts (M = Co, Ni, Cu): solid-state structure and electrochemical, electronic and magnetic properties of bi- and tetrametallic complexes and coordination polymers

The synthesis and characterisation of a series of novel complexes of type [((tmeda) M-OC(O)-fc-(mu-CO2)) (2)(mu-H2O)] (M = Co, 4; M = Ni, 5), zwitter-ionic [((pmdta)(H2O) Cu+-OC(O)-fc-CO2-)(CH3OH)] (9), and coordination polymer [(tmeda) Cu((OC(O))(2)fc)](n) (7) (fc = ferrocene-1,1'-diyl, (eta(5)-C5H4)(2)Fe; tmeda = N,N,N',N'-tetramethylethylenediamine; pmdta = 1,1,4,7,7-N,N,N',N '',N ''-pentamethyldiethylenetriamine) composed of ferrocene dicarboxylates and [(tmeda)/(pmdta)M](2+) entities is reported. These complexes could be prepared from [M(NO3)(2)(tmeda)] (M = Co, 2; M = Ni, 3; M = Cu, 6) and [Cu(NO3)(2)(pmdta)] (8), respectively, with stoichiometric amounts of 1,1'-ferrocene dicarboxylic acid (1) in presence of [n-Bu4N]OH-H2O. The molecular structures of 4, 5, 7, and 9 in the solid state have been determined by single-crystal X-ray structure analysis. Electrochemical and UV-vis-NIR spectroscopic studies of these complexes are discussed in terms of electronic communication between the redox-active transition metals. In addition, the magnetic properties of 4 and 5 have been studied by susceptibility measurements vs. temperature. In complex 4, the two cobalt(II) ions are antiferromagnetically coupled, while in 5 the Ni-Ni coupling is ferromagnetic with J approximate to +2.2(1) cm(-1).