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 (CH 3 CN)(N3Py 2Ph SEtCN)](BF 4 ) 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 (CH 3 CN)(N3PySEtCN)(BF 4 ) 2 . Reaction of 1 with NO (g) in CH 3 CN yields an {FeNO} 7 ( S = 3 / 2 ) complex 2 , which slowly decays at 25 °C with loss of NO • to regenerate 1 . One-electron reduction of 2 with Cr(C 6 H 6 ) 2 at -40 °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.