A comparison of ferrocenyl carbenium/non-carbenium structures in isomeric osmium cluster complexes obtained from the reaction of bis-ferrocenylbutadiyne with Os3(CO)10(μ-py)(μ-H)

The reaction of Os3(CO)10(μ-η2-py)(μ-H) (1) (py=NC5H4) with 1,4-bis(ferrocenyl)butadiyne (2) in the presence of Me3NO has provided two new isomeric triosmium cluster compounds Os3(CO)9(μ-py)(μ3,η3-CCFcCCHFc) (3) (Fc=C5H4FeC5H5) and Os3(CO)9(μ-py)(μ3,η2-CCFcCCHFc) (4). Both products were characterized by IR, 1H-NMR and single crystal X-ray diffraction analysis. Both compounds contain a triply bridging 1,3-bisferrocenylallylcarbyne ligand in an open triosmium cluster. Two of the carbon atoms of the allyl portion of the bisferrocenylallylcarbyne ligand in 3 are coordinated to one osmium atom, but in 4 only one of these carbon atoms is coordinated, and the other carbon atom forms a planar trivalent carbenium center. The bisferrocenylallylcarbyne ligand was formed by insertion of 2 into the osmium-hydrogen bond and a 1–2-shift of one of the ferrocenyl groups along the butadiyne chain. Both compounds exhibit two reversible one electron oxidations for the ferrocenyl groups: for 3, Ep=+0.34 and +0.67 V; for 4, Ep=+0.47 and +0.61 V.