Evidence for an Unusual Thermally Induced Low-Spin (S=1/2) ⇄ Intermediate-Spin (S=3/2) Transition in a Six-Coordinate Iron(III) Complex: Structure and Electronic Properties of a (1,2-Benzenedithiolato)iron(III) Complex ContainingN,N′-Dimethyl-2,11-diaza[3.3](2,6)pyridinophane as Ligand

A thermally populatedS=3/2 spin state at room temperature is quite unusual for the coordination chemistry of six-coordinate iron(III) ions. For the complex cation [Fe(L-N4Me2Me2)(S2C6H4)]+, the occurrence of a spin crossover between a low-spin state and an intermediate-spin state is established by structural, magnetic and spectroscopic evidence.