Doubly Pyrazolate-Bridged Dinuclear Complexes of a Highly Constrained Bis-terdentate Ligand: Observation of a [High Spin-Low Spin] State for [Fe II 2 (PMAP) 2 ][SbF 6 ] 2 ·2.25(C 3 H 8 O) (PMAP = 3,5-bis{[ N -(2-pyridylmethyl)amino]-methyl}-1 H -pyrazolate)