206977-46-0Relevant academic research and scientific papers
(Nitro)Iron(III) Porphyrins. EPR Detection of a Transient Low-Spin Iron(III) Complex and Structural Characterization of an O Atom Transfer Product
Munro, Orde Q.,Scheidt, W. Robert
, p. 2308 - 2316 (1998)
The reaction of BF3·OEt2 with the bis(nitro) complex of iron(III) picket-fence porphyrin, [K(18C6)(OH2)][Fe-(TpivPP)(NO2)2], leads to the formation of a transient porphyrin intermediate, assigned on the basis of its rhombic low-spin EPR spectrum as the five-coordinate N-bound mono(nitro) iron(III) derivative, [Fe(TpivPP)(NO2)]. This species is reactive and readily undergoes oxygen atom transfer to form [FeIII(TpivPP)(NO3)] and [FeII(TpivPP)-(NO)]. The reactions have been followed by EPR and IR spectroscopy. [Fe(TpivPP)(NO2)] has a rhombic EPR spectrum (g = 2.60, 2.35, and 1.75) in chlorobenzene and CH2Cl2 and is spectroscopically distinct from the bis(nitro) starting material (g = 2.70, 2.50, and 1.57). Oxidation of the nitrosyl species to [Fe(TpivPP)(NO3)] proceeds via an intermediate assigned as [Fe(TpivPP)(NO2)J on the basis of its EPR spectrum. The crystal structure of one of the reaction products, [Fe(TpivPP)(NO3)], has been determined. The nitrate ion of [Fe(TpivPP)(NO3)] is bound to the iron(III) ion in a symmetric bidentate fashion within the ligand-binding pocket of the porphyrin pickets. Individual Fe-O distances are 2.123(3) and 2.226(3) A?. The dihedral angle between the plane of the nitrate ion and the closest Np-Fe-Np plane is 10.0°. The Fe-Np bonds (and trans Np-Fe-Np angles) perpendicular and parallel to the plane of the axial ligand average to 2.060(5) A? (154.84(9)°) and 2.083(3) A? (146.14(9)°), respectively. Crystal data for [Fe(TpivPP)(NO3)]: a = 23.530(2) A?, b = 10.0822(5) A?, c = 48.748-(3) A?, β = 92.145(5)°. monoclinic, space group 121 a, V= 11556.4(14) A?3, Z= 8, FeN9O7C64H64, 8798 observed data, R1 = 0.0606, wR2 = 0.1313, all observations at 127(2) K.
Structural and physical characterization of (nitrato)iron(III) porphyrinates [Fe(por)(NO3)] - Variable coordination of nitrate
Wyllie, Graeme R.A.,Munro, Orde Q.,Schulz, Charles E.,Robert Scheidt
, p. 4664 - 4672 (2008/10/09)
We report the X-ray crystal structures of two different iron(III) porphyrinates: [Fe(OEP)(NO3)] and [Fe(TPP)(NO3)]. The first complex has the nitrate ion coordinated by a single oxygen atom while the second derivative has the nitrate coordinated in a symmetric bidentate fashion. This latter structure is a redetermination that shows some differences from an earlier structure; the difference appears to be the result of an unrecognized nitrate ion disorder in the earlier structure determination. Changes in physical properties of three species [Fe(TPivP)(NO3)], [Fe(OEP)(NO3)], and [Fe-(TPP)-(NO3)] as a function of coordination mode were examined by M?ssbauer and EPR spectroscopies; EPR spectra appear to be most sensitive to the change in coordination mode.
