Mononuclear, Nonheme, High-Spin {FeNO}7/8 Complexes Supported by a Sterically Encumbered N4S-Thioether Ligand

The synthesis of a new nonheme iron NO binding complex, [Fe-II(CH3 CN)(N3Py(2ph)SEtCN)](BF4)(2)(1), is reported. Complex 1, which contains two sterically encumbering phenyl substituents, exhibits a high-spin (hs) Fe-II (S = 2) ground state in contrast to the S = 0 ground state for unsubstituted [Fe-II(CH3CN)(N3PySEtCN)-(BF4)(2). Reaction of 1 with NO(g) in CH3CN yields an {FeNO}(7) (S = 3/2 ) complex 2, which slowly decays at 25 degrees C with loss of NO center dot to regenerate 1. One-electron reduction of 2 with Cr(C6H6)(2) at -40 degrees C yields the metastable, S = 1 {FeNO}(8) complex 3. The nitrosyl moieties in thioether-ligated 2 and 3 are significantly less activated than in thiolate-ligated [Fe(NO)(N3PyS)](+/0), a structurally analogous pair of hs {FeNO}(7/ 8) complexes. Calculations reveal that reduction of 2 is iron-centered, which may be a general property of hs {FeNO}(7/8) complexes.