Low-Coordinate Iron(II) Amido Complexes of β-Diketiminates: Synthesis, Structure, and Reactivity

The synthesis, structure, and reactivity of a series of low-coordinate Fe(II) diketiminate amido complexes are presented. Complexes LRFeNHAr (R = methyl, tert-butyl; Ar = para-tolyl, 2,6-xylyl, and 2,6-diisopropylphenyl) bind Lewis bases to give trigonal pyramidal and trigonal bipyramidal adducts. In the adducts, crystallographic and 1H NMR evidence supports the existence of agostic interactions in solid and solution states. Complexes LRFeNHAr may be oxidized using AgOTf, and the products LRFe(NHAr)(OTf) are characterized with 19F NMR spectroscopy, UV/vis spectrophotometry, solution magnetic measurements, elemental analysis, and, in one case, X-ray crystallography. In the structures of the iron(III) complexes LRFe(NHAr)(OTf) and LRFe(OtBu)(OTf), the angles at nitrogen and oxygen result from steric effects and not π-bonding. The reactions of the amido group of LRFeNHAr with weak acids (HCCPh and HOtBu) are consistent with a basic nitrogen atom, because the amido group is protonated by terminal alkynes and ...