Synthesis, spectroscopic and structural characterization of the high-spin Fe(II) cyanato-N and thiocyanato-N 'picket fence' porphyrin complexes

摘要

Two new iron(II) five-coordinated porphyrin complexes [Na(2,2,2-crypt)] [Fe~(II)(TpivPP)(NCO)] (1) (TpivPP = α,α,α,α- tetrakis(o-pivalamidophenyl) porphyrin known as picket fence porphyrin and 2,2,2-crypt is the cryptand-222) and [K(2,2,2-crypt)][Fe~(II)(TpivPP) (NCS)] (2) have been prepared and characterized. The UV-Vis and IR spectroscopic data are consistent with a cyanato-N and thiocyanato-N ferrous porphyrinates. The M?ssbauer data and the X-ray structural analysis indicate that the Fe(II) cation in 1 and 2 is high-spin (S = 2) and has the (dxy)2(dxz)1(dyz) 1(dz2)1(dx2-y2)1 ground state electronic configuration. For complex 1, the average equatorial iron-pyrrole N bond length (Fe-N_p = 2.120(2)), the distance between the iron and the 24-atom mean plane of the porphyrin ring (Fe-P_C = 0.6805(7)) and the distance between the iron and the plane made by the four pyrrole nitrogens (Fe-P_N = 0.5923(12)) are longer than those of complex 2 and similar five-coordinated Fe(II) high-spin porphyrinates. This is probably due to the significant electronic repulsion of the dx2-y2 and d_(xy) orbitals by the negative charge of the pyrrole N atoms in case of 1.