Abstract Mr = 460.36, monoclinic. P21/c, a = 13.718(1), b = 11.090(1), c = 14.985(1) Å, β = 98.162(2)°, V = 2256.67(9) Å3, Z = 4, Dx = 1.355 Mgm−3, μ = 0.933 mm−1, F(000) = 968, room temperature, final R = 0.047 (Rw = 0.048) for 3184 [I ⩾ 3 σ(I)] observed reflections. The title compound has the “three-legged piano stool” geometry, i.e. the coordination geometry of the iron can be regarded as a distorted octahedron with aη 5 – C5Me5 group occupying three coordination sites. Like its nonmethylated analogue it contains an unusually monodentate dithiophosphate ester ligand.