Solution structures and dynamics of [HOs₃(CO)₁₀(σ,π vinyl)] complexes

No interconversion has been found to occur on the NMR time scale between the structural arrangements found in the solid state. The σ, π motion of the vinyl group does not cause a cis-trans interconversion of the terminal hydrogens in [HOs₃(CO)₁₀(CHCH₂)] which simply takes place by alternating the π-electron cloud to opposite osmium centres. The ¹H chemical shift of the =C {A figure is presented} moieties is a useful probe to assess the coordination mode of the vinyl ligand. In [HOs₃(CO)₁₀(CPhC(H)Ph)], a trigonal twist process has been shown to occur at the Os(CO)₄ unit. For the same unit ²J_c-c trans have been obtained for all the reported derivatives and their magnitude is almost unchanged along the series. Further J_cc information has been obtained from a sample of [HOs₃(CO)₁₀(CHCH₂)] C-13 labelled in the vinyl ligand.