Preparation and Molecular Stereochemistry of Six-Coordinate (Isothiocyanato)(pyridine)(porphinato)iron(III) Complexes. (Isothiocyanato)(meso-tetraphenylporphinato)(pyridine)iron(III), a Low-Spin Complex with a Nonlinear Fe-N-C-S Group, and (Isothiocyanato)(octaethylporphinato)(pyridi...

Article abstract of DOI:10.1021/ja00376a021

The preparation and characterization of two six-coordinate (porphinato)iron(III) derivatives having the mixed-axial ligation of pyridine and isothiocyanate is described.One derivate, (isothiocyanato)(meso-tetraphenylporphinato)(pyridine)iron(III), Fe(TPP)(py)(NCS), is essentially a low-spin (S = 1/2) complex while the second derivative, (isothiocyanato)(octaethylporphinato)(pyridine)iron(III), Fe(OEP)(py)(NCS), is a high-spin (S = 5/2) complex.The crystal and molecular structure of the two complexes has been determined.The structure determination of Fe(OEP)(py)(NCS) is the first high-spin six-coordinate iron(III) porphyrinate having nonequivalent axial ligands to be characterized.The structure of Fe(TPP)(py)(NCS) is that expected for a low-spin (porphinato)iron(111) species with an average Fe-N_p distance of 1.988 (9) Angstroem, Fe-N(py) = 2.082 (3) Angstroem, and Fe-N(NCS) = 1.942 (4) Angstroem .The Fe-N-C-S group is partly bent with an Fe-N-C angle of 155.6 (3) deg.The bending is attributed to packing interactions in the solid state.The structure of Fe(OEP)(py)(NCS) shows an average increase in bond distance of 0.115 Angstroem which is quite anisotropic in distribution: average Fe-N_p = 2.048 (4) Angstroem, Fe-N(py) = 2.442 (2) Angstroem, Fe-N(NCS) = 2.031 (2) Angstroem .The iron(III) atom is displaced by 0.24 Angstroem from the mean plane of the core toward the isothiocyanate ligand.The Fe-N-C-S group is linear.Crystal data for Fe(TPP)(py)(NCS): a = 13.238 (3) Angstroem, b = 23.917 (5) Angstroem, c = 14.269 (3) Angstroem, and β = 104.74 (1) deg, Z = 4, space group P2₁/n, 5878 unique observations used in the structure determination.Crystal data for Fe(OEP)(py)(NCS): a = 12.348 (3) Angstroem, b = 15.625 (4) Angstroem, c = 10.535 (2) Angstroem, and α = 92.30 (2) deg, β = 105.10 (2) deg, γ = 101.10 (2) deg, Z = 2, space group P1/, 7549 unique reflections.