The adsorption of benzene on the magnetic Fe-6 Cluster was studied by means of first principles all-electron calculations done with gradient corrected density functional theory. In the M = 2S + 1 = 13 (S is the total spin) ground state (GS) of Fe-6-(C6H6)(3) each benzene is bonded with one Fe atom, forming eta(6) coordinations with C-Fe contacts of 2.12-2.17 angstrom; though the Fe-6 cluster structure is preserved, it presents more distortion than in bare Fe-6. The M = 13 GS of Fe-6-(C6H6)(4) shows a more distorted geometry with three eta(6) and one eta(2) coordinations, as the bonding with the fourth benzene was reduced to two C-Fe bonds. Thus, Fe-6-(C6H6)(4) may be viewed as a Fe-6 core covered by a layer of benzene molecules. The d-pi bonding interactions are clearly reflected by the estimated adiabatic ionization energies (4.60 and 4.42 eV for in = 3 and 4, respectively), because they are significantly smaller than that of bare Fe-6, 6.15 eV. The adiabatic electron affinities also are diminished clearly, 1.02 and 1.13 eV, for in = 3 and 4, respectively, as compared to that of Fe-6, 1.61 eV. The magnetic moments of the Fe-6-(C6H6)(3,4) complexes are strongly quenched, by 8.0 magneton bohrs (mu(B)), with respect to the value, 20.0 mu(B), of the isolated Fe-6 Cluster. Lastly, the vibrational spectra show IR bands placed near those of free benzene and several forbidden IR modes of benzene turn IR active in the reduced symmetry of the complexes.