[en] seven coordinate ; high-spin iron ; Mössbauer spectroscopy
[en] We present a new structurally determined seven-coordinate iron platform supported by the tris(2picolyl)amine ligand 6,60 -(pyridin-2-ylmethylazanediyl)bis(methylene)bis(N-tert-butylpicolinamide) (TPA 2C(O)NHtBu, 3) and its reactivity with oxo and nitrene transfer agents. Oxidation of the pentagonal bipyramidal, seven-coordinate iron(II)–triflate complex [TPA 2C(O)NHtBuFeII(OTf)][OTf] (4) with PhIO produces the corresponding diiron(III) l-oxo complex [(TPA 2C(O)NHtBuFeIII) 2(O)][OTf]4 (5). Mossbauer and magnetic measurements on 5 in the solid-state establish antiferromagnetic coupling between its two Fe(III) centers. Reactions of 4 with the nitrene transfer agents PhINTs (Ts = p-MeC6H4SO2) and PhINNs (Ns = p-NO2C6H4SO2) provide the corresponding iron(III)-amide congeners [TPA 2C(O)NHtBuFeIII(NHTs)][OTf]2 (6) and [TPA 2C(O)NHtBuFeIII(NHNs)][OTf] 2 (7), respectively, affording a rare pair of isolable Fe(III)-amide compounds formed from nitrene transfer. By characterizing well-defined products in the crystalline form, derived from atom and group transfer to seven-coordinate iron, the collective data provide a starting point for the exploration of high-valent and metal–ligand multiply bonded species supported by approximate pentagonal-type ligand fields.