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 Os-3(CO)(10)(mu-eta (2)-py)(mu -H) (1) (py = NC5H4) with 1,4-bis(ferrocenyl)butadiyne (2) in the presence of Me3NO has provided two new isomeric triosmium cluster compounds Os-3(CO)(9)(mu -py)(mu (3),eta (3)-CCFcCCHFc) (3) (Fc = C5H4FeC5H5) and Os-3(CO)(9)(mu -py)(mu (3),eta (2)-CCFcCCHFc) (4). Both products were characterized by IR. H-1-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, E-p = + 0.34 and + 0.67 V; for 4, E-p = + 0.47 and + 0.61 V. (C) 2001 Elsevier Science B.V. All rights reserved.