Synthesis and redox chemistry of 1,1′-bis(diphenylphosphino)ferrocene derivatives of R2C2Co2(CO)6 (R  MeO2C, CF3)

Fe(C5H4PPh2)2 (dppf) undergoes facile thermal substitution reactions with R2C2Co2(CO)6 (R  MeO2C, CF3) to yield a variety of products. When R  MeO2C, initial coordination gives μ2-(MeO2C2)2C2Co2(CO)5(η1-dppf); its crystal and molecular structure, monoclinic, P21/c, a = 8.954(3), b = 20.211(2) c = 23.836(5)Å, β = 100.55(2)°, Z = 4, R1 = 0.0345 for 5764 reflections 1 > 2σ(1), confirms the monodentate coordination mode for dppf. At low dppf/alkyne-complex ratios, oligomeric products with dppf ligands linking up to five (μ2-MeO2C)2C2Co2 modules have been characterised but, as the proportion of the phosphine ligand increases. unstable products, which include a η1-μ-η1 dppf configuration, are obtained as well. In contrast, for R  CF3, only [(CF3)2C2]Co2(CO)4(η2-dppf) is found in significant yield. A molecule with two different reduction centres, [μ2-(MeO2C)2C2Co2(CO)5](μ-dppf)[Co3(μ3-CPh)(CO)8], was also characterised. Electrochemistry of the dppf complexes was characterised by fast ligand dissociation upon reduction of the (μ-alkyne)Co2 redox centre and oxidation of coordinated dppf. There was no evidence for communication between redox centres.