charge & multiplicity for ab-initio calc.

[tblee #*at*# camd.soongsil.ac.kr]

 Dear CCLers,
 I would like to know the setting of charge & multiplicity for benzene ring
 - metal atom(Al, Mg, Cu.....) system. As I know, the cation-pi electron
 interaction is strong, the starting structure is the binding between metal
 cation and benzene ring. My query is the value of charge & multiplicity for
 this non-neutral strcuture. In this case, the system is neutral or charged?
 From the geometry optimization calculation of the OH- ion,
 ----------------------------------------------------------------------------
 ------------
 INPUT :
 Gaussian generated by Cerius2
  -----------------------------
  Symbolic
 Z-matrix:
     Charge =-1 Multiplicity = 2
 OUTPUT :
  THE SPECIFIED CHARGE AND MULTIPLICITY ARE IMPOSSIBLE IN THIS MOLECULE.
 THE SUM OF THE ATOMIC NUMBERS IS 10, NATOMS IS  2
   ATOMIC NUMBER VECTOR
 8  1
  Error termination via Lnk1e in
 /usr/people/guest/g94/l301.exe.
 --------------------------------------------
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 I didn't know the proper value for this system and was very confused by
 this charged system!
 If some example about the charged system or the other calculation technique
 exist,
 it will be very helpful for me.