Low-coordinate iron complexes stabilized by N-(tert-hydrocarbyl)anilide ligation: Adduct formation, chemical oxidation, and nitric oxide complexation

Monomeric iron complexes supported by the new, sterically-demanding NRAr(F) (R = C(CD3)(2)CH3, Ar-F = 2,5-C(6)H(3)FMe) and NR'Ar-F (R' = C(CD3)(2)Ph) ligands are described. Four-coordinate Fe(Cl)(TMEDA)(NRAr(F)) (1) was isolated in 87% yield as a colorless solid. The bis(amide) complexes Fe(L)(NRAr(F))(2) (L = pyridine-d(5), 2; L = PEt(3), 3) were isolated in 91% and 80% yields as orange-red and yellow solids, respectively. The related complex Fe(py-d(5))(NR'Ar-F)(2) (4) was prepared in 79% yield, characterized structurally by X-ray diffraction, and found to display chelation of the Ar-F residue via dative Fe ... F interactions. The iodo complex Fe(I)(py-d(5))(NRAr(F))(2) (5) was obtained in 91% yield as a purple solid upon treatment of 2 with 1/2 equiv of iodine; according to an X-ray diffraction study 5 is a pseudotetrahedral monomer. The nitric oxide complexes Fe(NO)(L)(NRAr(F))(2) (L = py-d(5), 6; L = PEt(3), 7) were obtained as wine red crystalline solids in 92% and 89% yields, respectively, upon treatment of 2 or 3 with a slight excess of-gaseous nitric oxide. Nitric oxide abstraction from 6 was accomplished quantitatively upon treatment with Mo(NRAr)(3) (Ar = 3,5-C(6)H(3)Me(2)) or with Cr((NPr2)-Pr-i)(3), regenerating 2 and generating Mo(NO)(NRAr)(3) or Cr(NO)((NPr2)-Pr-i)(3). The homoleptic iron(II) amide [Fe(NRAr)(mu-NRAr)](2) (8) was obtained in 88% yield as a red-orange solid upon treatment of ethereal ferrous chloride with 2 equiv of Li(NRAr)(OEt(2)). ''Ate'' complex (ArRN)Fe(mu-NRAr)(2)Li(OEt(2)) (9) was obtained similarly through treatment of ferrous chloride with 3 equiv of Li(NRAr)(OEt(2)). Ferrocenium triflate oxidation of 9 gave the homoleptic iron(III) amide Fe(NRAr)(3) (10) in 85% yield. All paramagnetic complexes studied here were characterized by magnetic susceptibility studies, by H-2 NMR spectroscopy, and by elemental analysis.