Square-planar high-spin Fe(II) molecular compounds are rare, and until recently, the only four examples of nonmacrocyclic or sterically driven molecular compounds of this kind shared a common FeO4 core. The trianionic pincer-type ligand [CF3-ONO]H-3 (1) supports the high-spin square-planar Fe(II) complex {[CF3-ONO]FeCl}{Li(Sv)(2)}(2) (2). In the solid state, 2 forms the dimer complex {[CF3-ONO]Fe}(2){(mu-Cl)(2)(mu-LiTHF)(4)} (3) in 96% yield by simply applying a vacuum or stirring it with pentane for 2 h. A detailed high-frequency electron paramagnetic resonance and field-dependent Fe-57 Mossbauer investigation of 3 revealed a weak antiferromagnetic exchange interaction between the local iron spins which exhibit a zero-field splitting tensor characterized by negative D parameter. In solution, 2 is in equilibrium with the solvento complex {[CF3-ONO]FeCl(THF)}-{Li-2(Sv)(4)} (2 center dot Sv) and the dimer 3. A combination of frozen solution Fe-57 Mossbauer spectroscopy and single crystal X-ray crystallography helped elucidate the solvent dependent equilibrium between these three species. The oxidation chemistry of 2 center dot Sv was investigated. Complex 2 reacts readily with the one-electron oxidizing agent CuCl2 to give the Fe(III) complex {[CF3-ONO]FeCl2}{Li(THF)(2)}(2) (4). Also, 2 center dot Sv reacts with 2 equiv of TlPF6 to form the Fe(III) complex [CF3-ONO]Fe(THF)(3) (5).