A comparison of ferrocenyl carbenium/non-carbenium structures in isomeric osmium cluster complexes obtained from the reaction of bis-ferrocenylbutadiyne with Os 3(CO) 10(μ-py)(μ-H)

Abstract

The reaction of Os 3(CO) 10(μ-η 2-py)(μ-H) ( 1) (py=NC 5H 4) with 1,4-bis(ferrocenyl)butadiyne ( 2) in the presence of Me 3NO has provided two new isomeric triosmium cluster compounds Os 3(CO) 9(μ-py)(μ 3,η 3-CCFcCCHFc) ( 3) (Fc=C 5H 4FeC 5H 5) and Os 3(CO) 9(μ-py)(μ 3,η 2-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, E p=+0.34 and +0.67 V; for 4, E p=+0.47 and +0.61 V.