CCL:G: Ferrocenium cation

Why is there a problem?  If you are using Mulliken charges, no one takes
 those seriously.  If you are using electron topology-based methods, there
 is probably no problem.  The formal charge of the ferrocenium ion is 1.  It
 does not mean that the charge of the iron is 1.  The overall charge of the
 molecular species is +1.  Just because a result conflicts with your
 chemical intuition does not mean your intuition is right and the
 calculation is wrong.  I'd say ensure the charge derivation method you are
 using is appropriate for the level of theory you are using and interpret
 the results as they are and not what you want them to be.
 On Mon, Nov 9, 2015 at 8:06 PM, Dusan Petrovic dupet100++hhu.de <
 owner-chemistry^-^ccl.net> wrote:
 >
 > Sent to CCL by: "Dusan  Petrovic" [dupet100|hhu.de]
 > Hi,
 >
 > While the calculation of ferrocene was rather straightforward (B3LYP/6-
 > 311++G** and LANL2DZ for iron), calculation of the ferrocenium ion (Fc+)
 > generates problems.
 >
 > During Fc oxidation, one electron is removed from an orbital that formally
 > belongs to iron (which should change iron's oxidation state from Fe+2 to
 > Fe+3). Therefore, I expected that the partial charge on iron in Fc+ will be
 > close to 1 (it was ~0 in Fc).
 >
 > Geometry optimization works well (I tried B3LYP, M06 and B97D functionals
 > with either pure 6-311++G** or mixed 6-311++G**/ LANL2DZ with ECP in
 > Gaussian). The cation multiplicity was set to 2, as the literature suggests
 > a low spin state. However, calculated ESP charge on iron in Fc+ is
 > negative,
 > while hydrogen
 > atoms have relatively high positive charge. Both restricted and
 > unrestricted
 > open shell calculations show very similar results (-0.033 for C, 0.165 for
 > H
 > and -0.315 for Fe).
 >
 > Contrary to that, semiempirical PM7 partial charges look more reasonable:
 > -0.208 for C, 0.232 for H and 0.753 for Fe.
 >
 > What could be the cause of problems in the DFT calculations?
 >
 > Thanks,
 > Dusan>
 >
 >