Solution Structures and Dynamics of [HOs3(CO)10(sigma, pi-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, pi motion of the vinyl group does not cause a cis-trans interconversion of the terminal hydrogens in [HOs3(CO)10(CH=CH2)] which simply takes place by alternating the pi-electron cloud to opposite osmium centres. The 1H chemical shift of the =CHR moieties is a useful probe to assess the coordination mode of the vinyl ligand. In [HOs3(CO)10(CPh=C(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 Jcc information has been obtained from a sample of [HOs3(CO)10(CH=CH2)] C-13 labelled in the vinyl ligand.