Synthesis, characterisation, crystal structures and electrochemistry of triosmium nitrite carbonyl clusters containing ferrocenyl phosphines

The triosmium nitrite carbonyl cluster [Os3(μ-H)(CO)10(μ-η2-NO2)] (1) was allowed to react with 1,1′-bis(diphenylphosphino)ferrocene (dppf) and N,N-dimethyl-1-[(S)-2-(diphenylphosphino)ferrocenyl]ethylamine (ppfa) in the presence of Me3NO in CH2Cl2, and clusters [Os3(μ-H)(CO)8(μ-η2-NO2)(μ-dppf)] (2) and [Os3(μ-H)(CO)8(μ-η2-NO2)(μ-ppfa)] (3) were afforded in moderate yields. Clusters 2 and 3 were fully characterised by spectroscopic techniques and X-ray crystallography. The nitrite, hydride and the ferrocenyl phosphine ligands are all bridged across the same OsOs edge. The amine group of the ppfa ligand shows a preference to coordinate with the Os atom with a σ-bonded nitrite O atom. The redox properties of the nitrite complexes were investigated using cyclic voltammetry.