Ferrocene, point group

Unsymmetrically disubstituted (and hence chiral) metallocenes (with point group C,) such as the ferrocene 122) provide a rather special problem they were first defined as planar chiral 19) and the specification of molecular chirality (descriptors Rp and Sp) applied accordingly19). Several authors still classify these structures as planar chiral21 23-24). 

There are now no planes of symmetry. Hence, the point group is D5. Thus, as one ring in ferrocene is rotated relative to the other the symmetry... 

This situation affects all aspects of Chemistry. For example, ths frontier orbital theory of reaction mechanisms (57) stresses the symmetry properties of the highest occupied MO (HOMO) and of the lowest occupied MO (LUMO) of the reacting species in the point group of the transition state. Suppose we are discussing the protonation of ferrocene the question arises, what is the HOMO of the ferrocene molecule Is it the orbital given by Koopmans sequence of eigenvalues, or is it the 2g orbital whose energy on protonation may follow the ionization pattern and be hi er than that of the protonated orbital ... 

For each of the following, determine the molecular and corresponding crystallographic point groups (a) a piece of 8.5" x 11" paper (no lines), (b) staggered ferrocene, (c) eclipsed ferrocene, (d) hydrogen peroxide, (e) cyclopropane. 

Figure 3,21 Example molecules belonging to D a point groups (a) propa-1,2-diene, Did, (b) ferrocene, Djd.

A hypothetical cyclic voltammogram for the surface-confined redox reaction is shown in Figure 13.2. On the forward (positive-going) scan, an anodic wave is observed this wave is associated with oxidation of the -Fc groups (Fig. 13.1). This wave rises to a peak and then decays to zero current at potentials positive of the peak. This points out the first difference between a surface-confined redox reaction and a redox reaction in which the electroactive species is dissolved in solution. If the ferrocene were dissolved in the electrolyte solution... 

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