The single line mossbauer spectrum of [Fe(NH3)(6)](2+)

The Mossbauer spectrum of the [Fe(NH3)(6)](2+) cation consists of a single narrow line at room temperature This unusual effect is attributed to the existence of a dynamic Jahn-Teller distortion which inverts the t(2g) orbitals very rapidly such that the time-averaged q(valence) is zero. The observed splitting of 1500 cm(-1) in the 5(Eg) State in the electronic spectrum of [Fe(NH3)(6)]Cl-2 is consistent with this explanation. The Small ferrous quadrupole splittings in [Fe-II(CH3CN)(6)] [FeCl4](2) and [Fe(C6H5CN)(6)] [FeCl4](2), and the three line Mossbauer spectrum of [Fe(NH3)(6)]Cl-2 at 80 degrees K are also discussed.