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