The reaction of the four-coordinate picket fence iron(II) porphyrin complex [Fe(TpivPP)] with cryptand-solubilized KNO2 yields the five-coordinate porphyrin species [Fe(TpivPP)(NO2)](-). The six-coordinate complexes, [Fe(TpivPP)(NO2)(PMS)](-) and [Fe(TpivPP)(NO2)(Py)](-), are obtained when pentamethylene sulfide or pyridine is added anaerobically to the preformed five-coordinate porphyrin species; These novel species are characterized by UV-vis, IR, and Mossbauer spectroscopies as well as single-crystal structure determinations. The Mossbauer investigation shows that the isomer shifts and quadrupole splittings for [Fe(TpivPP)(NO2)(PMS)](-) and [Fe(TpivPP)(NO2)(Py)](-) are typical for six-coordinate, low-spin (S = 0) iron(II) porphyrinate complexes. This is in distinct contrast to the unusually large quadrupole splitting of the five-coordinate species [Fe(TpivPP)(NO2)](-). The molecular structures of [Fe(TpivPP)(NO2)(PMS)](-) and [Fe(TpivPP)(NO2)(Py)](-) show that the nitro groups are inside the "pocket" of the porphyrin trans to the neutral sulfur- or nitrogen-donating axial ligand. In all species, the projection of the nitrite ion onto the porphyrin plane bisects a N-p- Fe-N-p angle. In the pyridine derivative, the dihedral angle between the two axial ligand planes is 81.4 degrees. In the pentamethylene sulfide derivative, Fe-N-p = 1.990(6) Angstrom, Fe-N(NO2) = 1.937(3) Angstrom, and Fe-S(PMS) = 2.380(2) Angstrom, while in the pyridine derivative Fe-N-p = 1.990(15) Angstrom, Fe-N(NO2) = 1.951(5) Angstrom, and Fe-N(Py) = 2.032(5) Angstrom. In [Fe(TpivPP)(NO2)](-), Fe-N-p is 1.970(4) Angstrom while Fe-N(NO2) is a very short 1.849(6) Angstrom. The structural and spectroscopic data are interpreted as showing a significant difference in the [Fe-NO2] pi interaction on change in coordination number.