Ruthenocene conformation

For ferrocene the symmetry of the space group requires the two five membered rings to have staggered conformation. In ruthenocene and osmocene the rings adopt the eclipsed conformation. 

Fig. 3.9 Molecular realizations of cylindrical symmetry (a) Dsh ruthenocene in an eclipsed pentagonal prismatic conformation and Dsd ferrocene in a staggered pentagonal antiprismatic conformation (b) top view of the pentagonal antiprism with the position of the five twofold axes perpendicular to the pentagonal direction (c) staggered conformation of triplet ethylene with D2J symmetry and horizontal. 4 axis (in the triplet the two carbon 2 >-orbitals shown are singly occupied) (d) alternative view of the D2d symmetry of a bisphenoid, with vertical S4 axis...

Let us first examine these sandwich metallocenes. Ferrocene has two isoenergetic conformations eclipsed (Da symmetry) and staggered (Dsd symmetry). X-ray crystallographic and electronic diffraction studies in the gas phase indicate an eclipsed conformation as well as for ruthenocene and osmocene. The rotation... 

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