AN IRON-CARBONYL DERIVATIVE OF C-60 EXAMINED WITH MOSSBAUER-SPECTROSCOPY

Mossbauer measurements performed between 5 and 300 K on polycrystallin e powder of an iron-carbonyl derivative of C-60 reveal two inequivalen t iron sites. The first site displays a quadrupole split doubler at al l temperatures, assigned to an [{Fe(CO)(4)}(x)(eta(2)-C-60)] adduct (X unknown). This iron site presents an S = 0 spin state and a negative isomer shift indicating that C-60 acts as an electron pair donor to th e metal center. The average effective hyperfine field for the second s ite is characteristic of an Fe(III) high-spin (S = 5/2) state and exhi bits relaxation effects, This Fe(III) sextet splits into two subspectr a, on the application of a magnetic field, which can be assigned to th e octahedral and tetrahedral sites of gamma-Fe2O3 microparticles forme d on the grain surface.