Infrared, Magnetic, Mössbauer, and Structural Characterization of Fe(TPP)(OReO₃)·tol (TPP = Dianion of Tetraphenylporphyrin; Tol = Toluene)


Perrhenatoiron(III) tetraphenylporphyrin has been isolated as its toluene solvate and characterized by using magnetic susceptibility, IR and Mössbauer spectroscopy, and single-crystal X-ray diffraction. Crystal data at 20°C are a = 12.228 (3) Å, b = 12.235 (3) Å. c = 15.968 (4) Å, α = 88.35 (2)°, β = 103.67 (2)°, γ = 113.18 (2)°, Z = 2, and space group P1. The iron atom is shown to be pentacoordinate with the perrhenate ion bound in a monodentate arrangement. The average Fe-N distance is 2.059 (7) Å, and the Fe-O bond distance is 2.024 (9) Å. The toluene molecules are present at a 43° angle to the porphyrin plane. No π-bonding between the solvent and porphyrin or between porphyrin moieties is evident. Two Re-O stretching and bending vibrations at 942, 827 cm-1 and at 336, 321 cm-1, respectively, also support the monodentate coordination of the perrhenate. The compound has a magnetic moment of 5.5 μB at 298 K arising from a quantum-mechanical admixture of S = 5/2 and S = 3/2 iron spin states in which the 5/2 state predominates. The 78 K Mössbauer spectrum shows a quadrupole doublet with parameters consistent with this admixture, and the spectral line shape may indicate the presence of electronic relaxation between the two states on the Mössbauer time scale. © 1990 American Chemical Society.



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© 1990 American Chemical Society (ACS), All rights reserved.

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01 Jan 1990