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

Two new iron(II) five-coordinated porphyrin complexes [Na(2,2,2-crypt)] [FeII(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)][FeII(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 Mössbauer 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 ( d xy ) 2 ( d xz ) 1 ( d yz ) 1 ( d z 2 ) 1 ( d x 2 - y 2 ) 1 ground state electronic configuration. mplex 1, the average equatorial iron-pyrrole N bond length (Fe–Np = 2.120(2) Å), the distance between the iron and the 24-atom mean plane of the porphyrin ring (Fe–PC = 0.6805(7) Å) and the distance between the iron and the plane made by the four pyrrole nitrogens (Fe–PN = 0.5923(12) Å) 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 d x 2 - y 2 and dxy orbitals by the negative charge of the pyrrole N atoms in case of 1.