Syntheses, structural characterisation and electronic structures of ferrocenyl-osmafuran heterobinuclear organometallic complexes.

The heterobinuclear complex OsCl2(PPh3)2[CHC(PPh3)CFcO] (Fc = (C5H4)Fe(C5H5)) (1) in which the two metal centers were connected by the skeleton of the osmafuran and cyclopentadienyl was synthesized via a one-pot reaction of OsCl2(PPh3)3 and FcCOC[triple bond, length as m-dash]CH in high yield. Three derivatives (Os(η2-OCOO)(PPh3)2[CHC(PPh3)CFcO] (2), Os(NCS)2(PPh3)2[CHC(PPh3)CFcO] (3), and OsCl2(dppb)[CHC(PPh3)CFcO] (dppb = Ph2P(CH2)4PPh2) (4)) were obtained by the ligand substitution reactions of complex 1 with different reagents (Cs2CO3 (2), NaSCN (3) and dppb (4)), respectively. All of these complexes were characterized by NMR spectroscopy and elemental analysis and the structures of complexes 1, 3 and 4 were further confirmed by single crystal X-ray diffraction. Their electrochemical properties were studied by cyclic voltammetry and square wave voltammetry. The first redox wave was ascribed to the couple Os(ii)/Os(iii). All of these complexes exhibit two redox processes with a large peak separation. However, UV-Vis-NIR combined with theoretical calculation clearly indicated that (1) the Os center plays a major role in the one-electron oxidation process of heterobinuclear complexes 1-4 and the osmafuran could be better described as a carbene ligand; (2) the electronic communication between the Os and Fe center is absent, and the osmafuran with the electron-withdrawing phosphonium substituent actually functioned as an insulating bridge.

Conformational Tuning of the Intramolecular Electronic Coupling in Molecular-Wire Biruthenium Complexes Bridged by Biphenyl Derivatives.

The synthesis and characterization of a series of biphenyl-derived binuclear ruthenium complexes with terminal {RuCl(CO)(PMe3)3} moieties and different structural arrangements of the phenyl rings are reported. Electrochemical studies revealed that the two metal centers of the binuclear ruthenium complexes interact with each other through the biphenyl bridge, and the redox splittings ΔE1/2 show a strong linear correlation with cos(2) ϕ, where ϕ is the torsion angle between the two phenyl rings. A combination of electrochemical, UV/Vis/NIR, and in situ IR differential spectroelectrochemical analysis clearly showed that: 1) the intramolecular electronic couplings in the binuclear ruthenium complexes could be modulated by changing ϕ; 2) the electronic ground state of the mixed-valent cations changes from delocalized to localized through the biphenyl bridge with increasing torsion angle ϕ, that is, the redox processes of these complexes change from significant involvement of the bridging ligand to an oxidation behavior with less participation of the bridge.