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

The heterobinuclear complex OsCl(PPh)[CHC(PPh)CFcO] (Fc = (CH)Fe(CH)) (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 OsCl(PPh) and FcCOC[triple bond, length as m-dash]CH in high yield. Three derivatives (Os(η-OCOO)(PPh)[CHC(PPh)CFcO] (2), Os(NCS)(PPh)[CHC(PPh)CFcO] (3), and OsCl(dppb)[CHC(PPh)CFcO] (dppb = PhP(CH)PPh) (4)) were obtained by the ligand substitution reactions of complex 1 with different reagents (CsCO (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.